Horizon (1964) s54e02 Episode Script
What’s The Right Diet For You? (2)
1 We are conducting one of Britain's biggest diet experiments.
It's based on the idea that instead of reaching for the latest fad diet, successful dieting should be tailored to each of us, as individuals.
We're working with Britain's leading obesity scientists for this unique study.
They've taken 75 overweight individuals and divided them into three groups based on their genes their hormones and their psychological profile.
So far, each group has been given a different diet, according to what makes them overeat.
But in this programme, we're going to find out what happens when our volunteers take their diets home.
We'll discover how our biology can make temptation difficult to resist It's hard, it's a hard slog.
Mentally, that is.
But I am winning.
.
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how understanding the brain reveals what makes us comfort-eat That explains why, when I get upset, straight to the cupboard.
Wow! .
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and what science can tell us about why we make disastrous food choices.
Let me tell you that this table managed a staggering 61,000 calories! We're one week into this ground-breaking experiment, and it's time to follow the volunteers as they return to the real world.
Until now, our dieters have been under constant supervision at our residential diet lab.
But now they're on their own, and it's time to see if they can put their new diets into practice in everyday life.
'I'm Chris van Tulleken.
'I'm a medical doctor and a research scientist.
' 'And I'm Professor Tanya Byron, a clinical psychologist.
'I often work with people with eating disorders.
'For this experiment, 'we've teamed up with specialists in obesity 'from Oxford and Cambridge Universities.
' We know that being overweight is due to overeating.
But people overeat for different reasons, and the latest science shows that it may be due to our individual make-up.
This series is about discovering the individual causes for overeating, and the answer could lead each of us to the perfect diet.
So far, our scientists have put the volunteers into one of three groups They have genes that increase their risk of obesity.
I've always maintained it was in my genes, and nobody would listen to me.
They comfort-eat in response to negative feelings.
The way I feel at t'minute I just want to cry.
They produce less of a hormone that tells them when they're full.
He's had about 12 plates already - more than half of his daily calories already, just in the first half of this meal.
Each group has been put on a different diet, designed to deal with their reasons for overeating.
And this is where the scientists are running the experiment from.
It's called the nerve centre, and it's here that they can monitor how the volunteers are doing, they can also track their data and their results, and also here they can come up with ideas and ways in which all the groups can cope better with their different diets.
Our dieters have now left the lab and are heading home.
They're going to have to stick to their diets with all the stresses and temptations of real life.
So the first group we're catching up with is the Constant Cravers.
Now, they're the ones who are always thinking about food.
The Constant Cravers were identified using genetic tests.
They scored highly for the genes that give them a stronger drive to eat.
And 51-year-old Mo Crookes is particularly unlucky - he's got many of these genes.
I'm constantly wanting to eat.
I'll graze.
I cannot sit down to three big meals a day because I just can't eat 'em, I'm stuffed.
I can't eat any more.
But I can eat constantly - every ten minutes, all through the day, I could put a sausage roll in me mouth.
At the diet lab, Mo learned all about the plan the scientists want the Constant Cravers to follow.
It's known as the intermittent fasting diet.
It means Mo and the Constant Cravers eat normally for five days, and then restrict their food intake for two.
On these fasting days, they're only allowed 800 calories - the equivalent of just a single meal, like a large curry.
Every diet I've ever seen, I've thought, "I can't stick to that, "I can't stick to that.
" Very defeatist before I've even started.
Now, with this knowledge that they've given me, this is the diet I thought I could achieve.
I've abused myself seven days a week, 52 weeks a year, all my life, so if I can't, for two days a week, for the next year or so, just pay back, pay the piper back And, in the end, I win.
I win, my family wins, we all win.
The fasting diet means our Constant Cravers only have to control their appetite for two days out of seven.
But today is a fasting day, and Mo's back at work as a volunteer driver for the ambulance service.
And there's danger lurking around every corner.
Every second shop appears to have something calling your name.
Like a sausage roll shouting, "Maurice! Come and eat me, Maurice!" There's KFC on every street corner, or McDonald's, or fish and chip shops Bloody Domino's Pizza there with a great big fat juicy pizza in the window! You've got a newsagents that sells Mars bars and chocolates.
Subway - there you go.
Mo's facing a problem we all have - we're constantly bombarded with adverts for food.
But Mo seems particularly drawn to them, so we've asked our scientists to investigate why this might be more of a problem for our Constant Cravers than other people.
Geneticist Dr Giles Yeo has arranged an experiment here at a fun park in Southend.
He wants to explore the effects that hungry genes have on our volunteers' behaviour.
Could they actually biologically programme our Constant Cravers to notice food more? Mo's here, along with fellow Constant Craver Danielle but, crucially, for comparison, so are Nikki and Sara from our other dieting groups.
Giles, this is not quite what I was expecting.
I was expecting a genetics lab and we seem to be at a funfair.
Ah, we can run experiments everywhere.
So, the point is, I'd like to really test how you guys interact with the world and, in particular, what you look at.
And to do this, Giles has brought with him an unusual pair of specs - eye-tracking glasses.
These record every tiny movement our volunteers' eyes make as they scan the environment .
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and so track precisely what they're looking at.
So I want you guys to put this on, wander around where your eyes will naturally actually go, OK for ten minutes, and we'll be able to see.
Giles asks everyone to take exactly the same route around the fun park.
# Oh, yes, I'm lookin' at the world Through rose-coloured glasses But he doesn't tell them the real goal of the experiment.
All around them, they see rides .
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hordes of people and, of course, food - loads of food.
And to up the ante, Giles has added some extra snack vendors and food signs.
Yes, everything is rosy no-o-ow! The experiment's over and the data is extracted from the glasses.
Giles analyses the results to see if there's a difference between what each dieting group looked at.
So, Giles, put us out of our misery.
What was that all about - what are the results? As I understand it, you guys had eaten already, so you shouldn't have been hungry.
No! The important and interesting thing that we actually found was that the Constant Cravers, as a group - that's Danielle and, in particular, actually, Mo - you guys spent a whole lot of A vast amount of your time looking at food, and not just the quantity of food, but the variety of food.
We can't keep on living like this Mo and Danielle's eye-tracking data reveals EXACTLY what they focused on.
MUSIC: Temptation by Heaven 17 # All I desire Temptation # Keep climbing higher and higher Temptation # Adorable creatures Temptation # With unacceptable features Temptation Trouble is coming Without any instruction from Giles, Mo alone clocked a total of 16 hits on food.
Despite the dieters from the other groups having their own issues with food, they averaged just six glances each.
In fact, the Constant Cravers were drawn to DOUBLE the number of food items compared with everyone else.
Remember, none of them knew what Giles was looking for in the experiment.
It's confirmation that Mo and the Constant Cravers see the world differently.
Did you know you were doing that, Mo? Yes.
Surprisingly, actually, because, as I say, I wasn't hungry at all, and then as you're going round, there's hot dogs and there's ice cream and there's crisps and people stuffing their faces full of chips and burgers, et cetera, and you're just looking at everything.
OK, so it seems like so far, so good.
The test we did at the funfair seems to back up what we know about people like Constant Cravers, but why, what's going on? What is happening with the Constant Cravers is and what happens is you are hungrier than other people.
You may be 5% hungrier than the person next to you, but that 5% hunger adds up over your lifetime - it actually adds up.
So it is part of your brain controlling the food intake, and your brain is feeling hungry all the time.
Being permanently hungry gives our Constant Cravers a greater drive to search out food.
But HOW are their genes making this happen in the first place? For most people, when our fat stores are at a sufficient level, signals are sent to our brain to tell us we don't need to eat.
But scientists have discovered Constant Cravers have genes which disrupt the way these signals are received.
They trick our brains into thinking the fat stores continually need to be replenished.
The result - they want to eat the whole time.
This is what it's like to be a Constant Craver, the reality of living with hungry genes.
So what can Mo and Danielle actually do about it? So, guys, problems are evident everywhere.
When you walk through town, you see all these food cues - they're trying to sell you a burger, they're trying to sell you sweets.
A useful strategy might be to think, "These guys are trying to sell me a burger.
" You know, almost conceptualise that your problem is the food company that's trying to sell - which they are! It's easier to think, "OK, I'm fighting someone else's urges, someone else's plan "to make ME buy the food," than it is for you to fight your own urges.
Yeah, I can see that working.
It's achievable, easily achievable.
But, like you say, there's going to be a lot of thinking at first.
And what do you think, then, about the strategy, which I? I'm not saying that all companies are bad, but the strategy of actually blaming it on someone else's urging you to buy the food Like you said, it passes the burden, doesn't it, so the burden's not solely on you.
Being aware of the power of food advertising is a technique anyone can try, but will it work for Mo? After the funfair experiment, he's back on his rounds.
My biggest let down, if you like, when I do get tempted without thinking about it, is when I fill up with fuel, cos I'm out every day, all day, driving.
When confronted with a world of treats, he's going to imagine it's all a battle with food companies instead of his own cravings.
So here we go.
I'm going to pay for the petrol, I'm going to get in me car and I'm going to leave.
And here we go, soon as I walk in, it's all there, staring at me - big bars of chocolate, biscuits, and I'm not having it, no.
They've told me how to deal with this, I can deal with this.
I'm just going to pay.
How are you? I'm fine, thank you.
How's yourself, OK? Good, thank you.
Thanks, all the best.
Cheers, goodbye! And goodbye to you, cos I'm not buying No chance.
No, no, I can resist.
I don't want There's nothing here I need.
I need to go.
There's nothing I need.
The techniques that came from the funfair It was absolutely It was an eye-opener, it really was an eye-opener.
And I'd say, so far, it's about 7-3 to me.
It's hard, it's a hard slog.
Mentally, that is, but I am winning.
Of course, these are still very early days for Mo and the rest of our Constant Cravers.
Back at the nerve centre, the experts are keeping tabs on all of the dieters.
Weight-loss data is streaming in from the 75 volunteers in the three dieting groups.
And this is where the scientists are collecting it for analysis.
The next group are our Emotional Eaters, so-called because they turn to food in emotional situations.
At the start of our experiment, we identified this group using psychological questionnaires.
We also saw how stress, brought on by a fake driving test, made them eat much more than the other two groups.
You know, how I feel at minute, I just want to cry.
As a clinical psychologist, I've treated many people who have difficult relationships with food.
It can happen for any number of reasons - stress, anxiety, or depression.
But sometimes, it's caused by traumatic events.
And that's what happened to Alison Vaughan.
When I'm stressed, when I'm anxious, I'll use going to the kitchen cupboard or the fridge as a distraction.
Alison Vaughan.
APPLAUSE AND CHEERING If I was angry I would eat, and I'd eat lots, I would stuff, basically.
I would comfort-eat quite a lot.
I've yo-yo dieted since I was 15 and I'm 53 now, so time to stop and perhaps take some control.
Alison's story is particularly harrowing.
Her problematic relationship with food started as a child.
My relationship with food Mmm.
It's been quite negative in the past.
And where that comes from That's as a result of being deliberately deprived of food when I was very small.
Alison was abused when she was younger.
She was starved of food, and bread and water was used as punishment at mealtimes.
If I'd been naughty, I wouldn't be allowed to run round the house with the other children.
I would have been in bed.
And then (It's OK, I'm not there now.
It's all right.
) And then I'd be called downstairs, and sat at this table.
And the table had a drawer in it, I remember.
And I'd be presented with this In fact, it'd be more soggy than that.
That's it - it would be well soaked.
And I'd be given that and I'd be given a spoon, and it'd be this size spoon.
And I'd be told that that was what I'd got to eat for my tea.
I think that's at the core, that's what kick-started things off in terms of food.
Nearly 50 years have since passed, and Alison is now happy.
She's married with a family.
But her troubled relationship with food remains, and she's hoping that science can help.
I feel quite relieved about being classified as an emotional eater, becauseit kind of gives you a footing from which to continue.
Because unless you can see what the issue is, you've really not got any hope of changing.
Alison's experience is extreme amongst our emotional eaters, but it can tell us something more general about why they all eat too much.
Our scientists are keen to discover what happens in their brain that compels them to comfort-eat.
'Alison and I have arranged 'to meet up at a research centre in Cambridge.
' Hello.
I'd just like to introduce you to Alison.
Hi, I'm Hisham.
'Neuroscientist Dr Hisham Ziauddeen is going to analyse Alison's brain 'when she's presented with food.
'To do this, he's going to use an fMRI scanner.
' How do you feel, are you all right? You're not claustrophobic, are you? No.
Well, I'll see you on the other side then.
Good luck, see you later! 'While she's being scanned, 'Alison's told she's about to be given something she likes.
'A chocolate milkshake - fed into her mouth by a tube.
' 'Two seconds before Alison receives the milkshake, 'the letter A appears on the screen in front of her.
'It means Alison can anticipate it before she actually tastes it.
' You'll then receive a little chocolate milkshake when there's a "taste" red flag up on the screen.
That OK? Yep.
'Hisham's focusing on one key region of Alison's brain.
The bit that we're interested in is actually plum here in the centre at the bottom.
And why we're interested in that area is that's where a lot of the brain's reward circuitry is based.
Food is obviously one of the most common biological rewards we encounter, but it's the same area of the brain that actually responds to other kinds of reward - be they money, be they drugs, be they sex.
It's telling you something coming in, or something out there, is pleasurable.
It also is doing the computations that allow you to act upon that pleasure - "Do I want to go and get it?" The activity in this area of the brain just before Alison gets the milkshake tells Hisham how much she desires it.
Alison is in a good mood for these first scans.
But for the next stage, Hisham wants her in a very different state of mind.
He's going to use a tried and tested psychological technique to induce a depressed mood.
You may feel a little down, but that's the whole idea of this session.
Alison's played sad music MUSIC: Adagio in G minor by Tomaso Albinoni .
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and made to read statements known to make people feel low.
MUSIC CONTINUES And in this mental state, she's again told to anticipate more milkshake.
The scans are complete, and Hisham's experiment is over.
Welcome back! I was crying in there.
Were you crying? Yeah.
Oh, no! So, are you all right now? Yeah, yeah, yeah.
'Clearly Alison felt sad, 'but what difference did it make to how her brain responded to food?' Alison, what we have here are a set of images of your brain from when you were lying in the scanner.
'In a good mood, 'Alison's brain activity increased in various places - 'including the all-important reward circuit.
' 'The greater the activity, the brighter the colours appear.
'Red is a low score, orange and yellow are higher, 'and white is the highest.
' So this is actually fairly typical of what you'd expect in most people's brains if we were presenting them with something that they liked, like a chocolate milkshake.
What I'm going to show you next is what happened after we did the mood induction, when you were feeling quite down and, again, we're going to look at your brain's anticipatory response when you were waiting for the milkshake to come with just the A on the screen.
'The reward circuit in her sad mood looks different.
' 'It glows bright white.
' 'Far more intense than when Alison was in a good mood.
' Wow! Gosh.
In that negative mood, the value of that particular milkshake that you were about to get was much higher.
That explains why, when I get upset, I'm straight to the cupboard - biscuits.
It's fascinating, isn't it? The big change we saw was in the anticipation.
It was.
Quite extraordinary.
'All our emotional eaters desire food more 'when they feel low, sad, stressed or angry.
' 'At those times, the kind of reaction we saw in Alison 'is very likely to be happening in their brains too.
' So, that was quite a revelatory experience.
Amazing.
I now know my own brain works against me, actually.
That's pretty much it, Hisham, is that right? There's a part of your brain that's conditioned to respond that way to food, and it has been doing that for years.
'Our scientists gave the emotional eaters a dieting plan 'that targets their particular problem with food.
' 'One part of this is group support.
'This uses the encouragement of others 'to help stop you turning to food when you're down.
' 'To get that support, 'our emotional eaters are all attending dieting clubs.
' Four and a half pounds off, Alison, well done.
Our scientists have also advised the emotional eaters to support each other online.
And they've recommended cognitive behavioural therapy, which helps them manage the thoughts, feelings and behaviours associated with comfort-eating.
To discover more about this kind of therapy - and the dieting strategies for all three groups in our ambitious diet experiment, head to: And if you're curious about what kind of eater you may be, go to the website and use our diet calculator to find out.
Back at the nerve centre, our scientists are busy keeping up with all our dieting groups.
So far, they've checked in with the constant cravers, and the emotional eaters.
The third and final group are the feasters.
Our feasters tend to overeat at mealtimes - once they start, they can't stop.
And that's because they just don't feel full.
In the assessments at the very start of our experiment, the scientists tested our volunteers' levels of one particular gut hormone.
At mealtimes, this hormone tells your body when you've eaten enough.
But we discovered our feasters produce much less of this.
This means the food they eat doesn't make them feel as full.
In the last episode, our scientists put on a never-ending sushi banquet but none of our volunteers knew it was actually a test.
Well, I've been watching Heidi, who has managed to power her way through about 12 dishes so far.
The feasters ate a LOT more than the other two groups.
And, in total, Heidi Locke polished off 15 plates.
That's over 2,000 calories even before the wine.
To the future! Yes.
Now, Heidi's back at work as an air hostess.
She's trying to stick to the diet our scientists gave feasters like her.
When I was told that I was a feaster and the reasoning and the science behind it, kind of a light bulb went on, you know? It makes sense now that I'm not producing enough of this gut hormone to tell myself to stop.
You know, "Stop eating, Heidi!" "No!" It's kind of nice to know that it's not just me - there's an actual physiological reason behind it.
Thinking that I have to tell myself to stop eating, my brain's not going to do it, and that's something that's a new tool in the box, if you will.
The diet we've given the feasters is designed to boost the feeling of fullness from meals.
Lots of protein and, also, foods with a low Glycaemic Index, or low GI.
These take a longer time to be processed by the gut.
So, what would the ideal meal for a feaster look like? A quarter would be lean protein, like chicken or fish.
A quarter low GI carbohydrates, like pasta or basmati rice.
And the remaining half? Vegetables.
For desserts and snacks, the feasters should stick to fruit.
This diet requires you to eat like this every day.
But it's just two weeks in, and Heidi's already finding it tough.
I didn't anticipate in any way, shape, or form, how hard it would be, and how difficult it would be to continually try to stick to it.
For Heidi, fruit and veg are no substitute for her favourite foods - pastries and cakes.
They have my favourites - I mean, they have the Bakewell slice, they have the cherry pie and my apple strudel.
Normally, I'd just be popping in there for something nice but, no, I'm just going to go for the fruit today.
The challenge Heidi faces is common to all our feasters.
If you're really fond of sugary and fatty foods, then suddenly changing your diet can be really difficult.
And what's even harder is substituting fruit and veg in place of those foods.
That's particularly true with veg.
So our scientists are hoping to discover if there's a way to get all the benefits of fresh vegetables, only without it seeming like a chore.
They're inviting all the feasters back to the diet lab to run some tests.
They want to know what happens inside the feasters' bodies after they eat either a plate of cooked veg or that same veg blitzed up with water into a soup.
Professor Fiona Gribble wants to see what's going on inside the feasters' stomachs, and she's going to use ultrasound.
First up - whole veg.
I'll be honest, ultrasound always looks like a badly-tuned telly to me.
What are we looking at here? You had chickpeas.
And what you can see here is the solid food within the stomach, which are these white areas here and very little in the way of gas, so the stomach is actually full with the food, and it's holding it there.
'Now, that's what you'd usually expect.
'Veg typically remains in the stomach for a couple of hours 'whilst it's being digested, 'and that actually helps our feasters feel full.
' Nice.
Now we know what a chickpea looks like on an ultrasound scan.
Or 100 of them! LAUGHTER Gut hormones aren't the only way we feel full when we eat.
There's another mechanism.
Our stomachs are lined with thousands of nerves.
They send signals to the brain about how full or empty the stomach is.
Bulky food like veg really stretches the stomach, stimulating those nerves.
That makes it filling, even for our feasters.
The food is still sitting in the stomach - the stomach will be having to work on that to break it down, to mix it with enzymes, break it down into small pieces before it will let it out of your stomach.
So while it's there, it should actually be stretching your stomach and sending signals back to your brain to say, "My stomach is full, it's still got this food in it, "don't eat any more.
" But there's a problem.
Many of the feasters don't enjoy this sort of food.
Not something I'd choose for a meal.
I didn't really enjoy it, obviously.
I couldn't eat any more.
So, what about the soup? Won't it just pass right through their stomachs, and not fill them up? I'm feeling like I'm pretty full.
I do feel quite full from just a small bit of soup, which is quite good.
That's really satisfied my appetite, that.
I'd like to know the recipe.
It seems as though the soup is making the feasters feel full, and Fiona knows why.
She's prepared a glass model of the stomach to help reveal how the soup can be just as filling as the veg.
The oesophagus drains food into it, and out of it you have an opening that goes into the intestines.
So, here's soup going into the stomach.
OK, so the soup is trickling through, but slowly.
That's right.
It's very well established that a thicker solution in the stomach will actually hold these food contents in the stomach for longer just because the nature is such that the food can't empty so quickly through this narrow gap, so that will give this greater sensation of fullness.
Thick soup stretches the stomach and, crucially, stays there for a long time.
That's why, in scientific tests, soup has sometimes been shown to fill you up even more than solid veg.
This is what makes it a handy dieting tool .
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especially for our feasters.
Our experiment is now well under way.
Regular video diaries from our dieters continue to pour in and nutritionalist Professor Susan Jebb is monitoring them from the nerve centre.
Everything's been superb.
Everything's gone brilliant.
Weighed myself on Saturday and I've lost approximately half a stone.
I've lost five pounds, which I'm over the moon at, because that takes me down to the next stone, so that makes you feel as if you're heading in the right direction.
Well, this is my second full week at Slimming World, just got back.
I've lost two and a half pounds this week, which I'm delighted with.
I've had to do my trousers up with an elastic band because, when I put my phone in my pocket, they fall down.
I have lost somewhere in the region of a stone.
I'm absolutely blown away by that.
That's mind-boggling to me.
I'm so delighted.
Well chuffed with myself.
That's a lot of very happy dieters.
It's a really good start and, as we can see here, the rate of weight loss in each of the three groups is pretty similar.
And what is the rate of weight loss on average? We were hoping that people would lose about two pounds a week.
In fact, on average, they're losing three pounds a week and, as we've heard, some people are losing much more than that.
'It sounds like fantastic news, 'but our dieters are about to get a cruel surprise.
'A substantial amount of that weight loss isn't actually fat.
' We know that people tend to lose weight more rapidly in the early weeks of the diet, and some of that is just a little bit of water loss.
So, we lose water at the beginning of a diet.
How much, in general, are we going to lose in those early weeks? Well, certainly a pound, maybe even two or three, but, by the end of the first week, it's probably mostly over.
The reason that water loss happens at the start of a diet is that, while the body begins to burn fat, it's also using up another temporary energy store - sugars stored in your liver and muscles.
All this sugar is kept in a solution with water.
For every one gram of sugar, there are about three grams of water and, when the sugar goes, your body loses that water too.
In some people, this can account for more than two pounds of weight loss.
Regardless of the diet we're on, most of us lose weight quickly at the start, but that inevitably slows down and progress begins to feel much harder.
So what can we do at this stage? Well, some of our dieters, from all three groups, have decided to try something they wouldn't normally do.
Exercise.
Whether it's classes at the gym, roller-skating, or swimming, time and again, it's the one thing recommended to go alongside a diet.
The popular belief is that exercise automatically helps you lose weight, but there's a catch.
In principle, weight loss should be pretty straightforward.
We just have to make sure we use up more calories than we eat.
So, on that basis, for our dieters, exercise should increase the amount of weight that they lose, but is it really that simple? We've called on a leading scientist in exercise, Dr Jason Gill from the University of Glasgow.
Until now, each experiment has targeted just one of our three groups, but all our dieting groups are exercising, so we've got a mix here today.
Brian, Derek, Susan, Nicola and Kirsty.
So what we're going to do is try to work out whether exercise can help us with weight loss.
So, to do that, we're going to get you to wear these devices, which are called accelerometers and they measure all your body's movements.
So I'm going to ask you to just tape it on to your thigh and leave it there for a week.
'Once fitted, the devices start monitoring their activity levels 'by counting the number of steps they take.
' So the more you move, the more calories you burn.
So all I want you to do is just wear these accelerometers for the next week and just carry on doing your normal daily activities, don't change anything.
For the first seven days, our five dieters are living life as normal with no additional exercise.
This gives Jason a measure of how much activity they do in a normal week.
It's their baseline.
But, for the second seven days, he's shaking things up a bit with a personal trainer who is going to put our dieters through hell.
Hold it! Ten, nine, eight, seven, six, five, four, four, three, two, one, up you come, well done.
Shake out the legs a little bit.
OK, we're going to go down.
Big strong push through the heel.
Try to work on your bum.
Jason wants to see what intensive exercise does to their bodies.
Lean back.
First two, you're off and away.
Oh, go you! Go you! Dynamo! Slow and controlled.
Bring the hand up.
Good.
Keep the bum down.
Keep the weight pushed forwards from your hips to your toes.
In just one week, our dieters endure three exercise sessions.
Can I just stay here and you just come back for me in the morning? Our volunteers don't know it, but this experiment isn't just about what they're doing in these sessions.
They'll keep wearing the accelerometers when they're back at home too.
What we're very interested in is the effect of this exercise session on their activities over the rest of the day and over the rest of the week.
Finally, the accelerometers are removed and Jason extracts the data.
Everyone's activity levels have been totalled up.
In the first week, without exercise, the group averaged 8,000 steps per day, but in the second week, on the three days they exercised, they averaged far more - over 11,000 steps.
So, that can be difficult to visualise, but we can visualise it in the form of a universal energy currency of swiss roll.
How much of the swiss roll do you think you burnt in your exercise sessions? One bit.
One bit.
OK, so A third of it.
A third.
So, we've got between a slice and a third.
You actually burnt off all of it.
Wow.
It's a good visualisation, isn't it? Are you pleased? Absolutely, yeah.
'Over the three days of exercise, 'each dieter burnt off the calorie equivalent of this much swiss roll.
'It seems impressive, 'but Jason's got bad news too.
' But there is a "but" here.
Yes, we measured what you did on the days when you did the planned exercise sessions, but we also measured what you did on the days when you didn't do the exercise sessions, and the graph looks something like this.
Here's the twist.
On the four other days, the ones when they weren't exercising, their general activity levels plummeted.
In fact, they did over 1,000 steps fewer than they normally would.
You look really surprised.
That surprised me, because I felt, after the exercise, I was really motivated and I got a real buzz off it, so I thought, the next day, I would be more empowered to do more, so that's really shocked me.
It's a well-known phenomenon.
So, what happens is you do your exercise and then, in the time when you're not exercising, you might actually do a little bit less activity than you would have done otherwise.
You think you've earnt a reward.
But there's a term for this, isn't there? Yeah, it's called compensation.
Compensation hits many of us after we exercise.
Either consciously or subconsciously, we rest up more than we normally would.
This can take a big slice off the total number of calories we use up over the week.
So, if we take this sort of whole swiss roll that you burnt in the sessions, you guys, with your compensation, actually lost about a third of it.
That goes away.
Oh! Oh.
That's still pretty good, but it's a third less because you're compensated.
Fortunately, Jason has a solution.
It's a little device called a pedometer and it lets our dieters see exactly how many steps they're doing every day.
They're not very expensive.
They're about £20.
So, what they do is they give you feedback and so, by giving you feedback, you have to sort of work to a goal and you can see whether you're achieving that goal.
You want to keep your steps up to your target and that stops you from doing the compensation and reducing the activity outside the planned activities.
And the idea is to build to a step number that's 3,000-4,000 per day more than you started off with.
Here's the truth about exercising while you diet.
You need to be really careful not to slob out on non-exercise days and, while exercise is really good for your overall health, the most effective way to lose weight will almost always be to change your diet.
It's nearly a month since the start of the experiment and, in all three groups, things are getting even tougher for our volunteers.
A bit of a harder day today for some reason.
It's the first day erm, that I've wanted things.
My weight loss seems to have ground to a halt this last week, which is a bit frustrating.
I must admit that it is frustrating, because I'm starting to starve, or I think I'm starving myself and not losing any weight at the moment.
I don't know why that is, but we'll have to wait and see.
Well, I went to slimming club last night and I've put on half a pound.
Gutted.
I've just had a A disastrous weekend, a disastrous week.
I just don't want to do this any more.
I want to lose weight and I want to lose it now.
My next-door neighbour has fish and chips and it's actually seeping through the walls and I can smell it.
So what's going on? Because we saw them two weeks ago and they were just full of life, loving it, no-one was complaining and they were all losing weight? Well, if we look at our group total weight loss here, what you can see is that the rate of weight loss really has started to slow down after that very successful first week.
So they lost masses there, and then much less over this period of time.
Yeah, and that's obviously pretty demoralising for people.
Losing weight requires real effort and mental energy, and that in itself is quite tiring.
Now that the honeymoon period is over, they're really reaching the point where it's getting hard to work up the energy and the motivation.
This tiredness, the mental fatigue you're talking about, that can't be helpful.
This is an incredibly risky time because there's a danger we get into a vicious cycle.
So, then, of course, they find it even harder to lose weight, they get more fatigued or tired and then the problem continues.
You're absolutely right.
It's a scary thought.
Tiredness in itself can lead to a diet failing.
And to investigate just how much tiredness can affect our ability to make good food choices, Susan's arranged a trip to the shops for our volunteers.
The thing is, there are so many temptations in life that can lead us away from healthy decision-making, but how can our state of mind impact on our ability to make those healthy decisions? A supermarket is a surprisingly dangerous place for our volunteers.
It's incredibly important, if you're going to stick to your eating plan, that you make the right choices whilst you're shopping.
Here you've got a choice of, you know, 20,000 or 30,000 different foods to choose from.
Once you're in your kitchen, you're stuck with the choices you've already made, so it's really important to get it right here.
Our experts think that, because of their psychology, the emotional eaters might be particularly vulnerable to the effects of tiredness.
So Susan has recruited ten of them for an experiment.
She's going to test the effects of exhaustion on the food they choose to buy.
First, she needs to mess with their sleep.
Five of them are going to bed early, while the rest have to keep each other entertained late into the night.
Swimming! It's currently 12:30.
We have to now stay up until three.
Shark.
Whale.
Godzilla.
Forgive me if I'm a bit cranky in the morning.
I do apologise.
Our five sleep-deprived dieters only get three hours' kip, so what difference will this make? The well-rested emotional eaters turn up at the supermarket bright-eyed and bushy-tailed.
The sleep-deprived team are rather more subdued.
Good morning, everybody.
So nice to see you.
You have slept all night, yes? Yes.
You haven't slept very much at all? So, you need to know why we're at the supermarket.
So, Susan, why don't you explain? So we want to do a shopping task for us.
I'm going to give you a list, £25 and just 20 minutes to go and do your shopping.
OK, are you up for the challenge? ALL: Yes.
It's like a game show, right? 'Both teams have just 20 minutes 'to buy four different categories of food.
' Oh, fish.
'A breakfast cereal' Oh, that's a bloody bargain, that.
£1.
99.
'.
.
a ready meal' Anybody can run.
'.
.
dinner for four' Pizza, garlic bread, mayonnaise.
'.
.
with drinks' Include drinks.
I need my drinks.
That'll do nicely.
'.
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and a snack that they want to eat right there and then.
' 'Of course, none of our dieters know what Susan is hoping to discover.
' Both teams finish and the food is laid out.
And it's immediately obvious that the tired group have made different choices to the rested group.
I'm sorry, I feel like we've tortured you here, in the name of science, but are you seeing differences in the tables? Yeah, their table looks a lot healthier compared to ours.
There's cake on our table.
There's a lot of cake on your table.
There's a stack of cake on your table.
Yeah.
Chantelle, did you make any specific choices shopping when tired? I did get a specific brand of pork pies because I was whizzing past and I thought, "Oh, I've just got to have them.
" What? Now? Yeah.
Right that second.
And why did you have to have them right that second? Because they're just really fatty and just really yummy, and fatty food's just good when you're tired and exhausted.
So, it's clear to everyone that there are some differences.
Susan's analysed everyone's shopping and the nutritional content starts to reveal the true extent of the problem for our tired shoppers.
There are two and a half times as much sugar in these breakfast cereals as our sleepers had in their choice of breakfast cereals.
So, we asked you to choose a ready meal.
When we look at what you've chosen, you might be surprised to hear that you've chosen more than three times as much saturated fat as you're well-rested colleagues over here.
But the biggest shock is when Susan compares everything the well-rested dieters bought to what the tired group bought.
This table over here, I can tell you that you're shopping today is about 37,000 calories.
That might seem a lot, but let me tell you that this table managed a staggering 61,000 calories.
That's more than one and a half times as many calories.
It might seem obvious that being tired can lead to a few poor choices, but Susan's experiment shows it's actually a dieting catastrophe.
Tiredness messes with your decision-making, increasing your desire for foods high in sugar and fat.
Yummy.
The reality of most people's lives is that they are time-starved.
Most of us are completely exhausted when we go shopping, so how can we avoid this, then? How can we make it different? Well, recognising that that's going to happen is really important, because if you know you're going to be caught out in the shop when you're tired, you can prepare for that in advance.
So if you know you're going to be going to do your big shop on the way home from work, then make a list the night before or the morning before, sometime when you're feeling fresh.
Make a plan, make a list, take it with you and stick to it.
If you do that whilst you're losing weight, then, over time, you will develop those new healthy habits and you will be able to just breeze in to the supermarket and make good choices.
We're bringing everyone back to our diet lab in Liverpool for their one-month weigh-in.
Yay! Hello! How are you? I hope you know I was married.
He ain't now! At the very start of the experiment, we set them the goal of losing more than 5% of their body weight in just three months through personalised dieting.
Other studies show that this is a tough target to reach.
Today, we're going to find out how they're getting on so far.
Good morning, everyone.
It's great to see you all back.
Now, you've been dieting for one month out of the three, so it's time for a checkup, and we want to find out how the diets are actually going for each of you.
The feasters have been following the fullness diet - rich in protein and low-GI foods.
What were you before, when we started? When we started I was 18.
9.
18.
1.
8 lbs.
8 lbs.
Yeah, I think that's fabulous.
I think that's fabulous.
The emotional eaters have been following the diet plan based on group support and using cognitive behavioural therapy.
So, you were before 17.
2.
And that says, now, 16.
8.
Yeah.
I'm very pleased with that 8 lbs.
You couldn't get into this dress before, could you? No, no.
This is an old dress that got too tight on you - and now look at you, you look great in it.
It's so nice.
'Finally, the constant cravers.
'They've been following the intermittent fasting diet.
' 22.
11.
What were you before, Brian? 24.
8.
So, you've lost almost 2st.
Far, far better than I expected.
It's the first diet I've ever done that I know I can stick to and I will stick to, and I can see it really long-term.
But not everyone is as pleased.
Let's have a look.
God, it's awful.
It's not even OK, what sort of loss is that? About 6 lbs.
No more than that.
And how are you about that? Not great.
I mean, I am a craver, I am a constant craver, so I am always thinking about food, day and night.
Admittedly, I'm honest, I haven't worked as hard as I should, I'm not going to deny it.
6 lbs in four weeks.
That's not bad.
That's healthy, that's slow, but that's steady.
It's slow, yeah.
Please don't think you've failed or you haven't worked hard enough.
You've done what you've done, now we kick up to the next gear.
Yeah.
Move up.
'So, that's individuals, 'but now we'll see how the whole group has fared overall 'and what progress they have made towards that target of 5%.
' OK, everybody, the numbers are in and, since our first weigh-in, you as a group have now lost in total 53st! That's amazing! Extraordinary! And, of course, as individuals, what that means is you've lost, each, on average, 4% of your body weight.
But, listen, the honeymoon period is over.
You're going to have to steel yourselves for the next couple of months.
You've got your targets, we know you can get there, but it is going to be tough.
What happens now is about whether or not you can turn what you've accomplished recently into long-term change.
So, good luck, everybody, and well done.
Well done.
If you want to see if you match up with one of our groups, head to .
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and use our diet calculator.
Discover which diet might suit you, your family or friends, and get more weight-loss tips.
Next time on What's The Right Diet For You?, our scientists bust the myths about metabolism, reveal the secrets of our most successful dieters That's a 25-kilo sack of chicken feed and that's just about what I've lost in weight.
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and discover how to keep weight off for ever.
It's going to give hope to millions of people out there who have dieted and failed in the past.
It's based on the idea that instead of reaching for the latest fad diet, successful dieting should be tailored to each of us, as individuals.
We're working with Britain's leading obesity scientists for this unique study.
They've taken 75 overweight individuals and divided them into three groups based on their genes their hormones and their psychological profile.
So far, each group has been given a different diet, according to what makes them overeat.
But in this programme, we're going to find out what happens when our volunteers take their diets home.
We'll discover how our biology can make temptation difficult to resist It's hard, it's a hard slog.
Mentally, that is.
But I am winning.
.
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how understanding the brain reveals what makes us comfort-eat That explains why, when I get upset, straight to the cupboard.
Wow! .
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and what science can tell us about why we make disastrous food choices.
Let me tell you that this table managed a staggering 61,000 calories! We're one week into this ground-breaking experiment, and it's time to follow the volunteers as they return to the real world.
Until now, our dieters have been under constant supervision at our residential diet lab.
But now they're on their own, and it's time to see if they can put their new diets into practice in everyday life.
'I'm Chris van Tulleken.
'I'm a medical doctor and a research scientist.
' 'And I'm Professor Tanya Byron, a clinical psychologist.
'I often work with people with eating disorders.
'For this experiment, 'we've teamed up with specialists in obesity 'from Oxford and Cambridge Universities.
' We know that being overweight is due to overeating.
But people overeat for different reasons, and the latest science shows that it may be due to our individual make-up.
This series is about discovering the individual causes for overeating, and the answer could lead each of us to the perfect diet.
So far, our scientists have put the volunteers into one of three groups They have genes that increase their risk of obesity.
I've always maintained it was in my genes, and nobody would listen to me.
They comfort-eat in response to negative feelings.
The way I feel at t'minute I just want to cry.
They produce less of a hormone that tells them when they're full.
He's had about 12 plates already - more than half of his daily calories already, just in the first half of this meal.
Each group has been put on a different diet, designed to deal with their reasons for overeating.
And this is where the scientists are running the experiment from.
It's called the nerve centre, and it's here that they can monitor how the volunteers are doing, they can also track their data and their results, and also here they can come up with ideas and ways in which all the groups can cope better with their different diets.
Our dieters have now left the lab and are heading home.
They're going to have to stick to their diets with all the stresses and temptations of real life.
So the first group we're catching up with is the Constant Cravers.
Now, they're the ones who are always thinking about food.
The Constant Cravers were identified using genetic tests.
They scored highly for the genes that give them a stronger drive to eat.
And 51-year-old Mo Crookes is particularly unlucky - he's got many of these genes.
I'm constantly wanting to eat.
I'll graze.
I cannot sit down to three big meals a day because I just can't eat 'em, I'm stuffed.
I can't eat any more.
But I can eat constantly - every ten minutes, all through the day, I could put a sausage roll in me mouth.
At the diet lab, Mo learned all about the plan the scientists want the Constant Cravers to follow.
It's known as the intermittent fasting diet.
It means Mo and the Constant Cravers eat normally for five days, and then restrict their food intake for two.
On these fasting days, they're only allowed 800 calories - the equivalent of just a single meal, like a large curry.
Every diet I've ever seen, I've thought, "I can't stick to that, "I can't stick to that.
" Very defeatist before I've even started.
Now, with this knowledge that they've given me, this is the diet I thought I could achieve.
I've abused myself seven days a week, 52 weeks a year, all my life, so if I can't, for two days a week, for the next year or so, just pay back, pay the piper back And, in the end, I win.
I win, my family wins, we all win.
The fasting diet means our Constant Cravers only have to control their appetite for two days out of seven.
But today is a fasting day, and Mo's back at work as a volunteer driver for the ambulance service.
And there's danger lurking around every corner.
Every second shop appears to have something calling your name.
Like a sausage roll shouting, "Maurice! Come and eat me, Maurice!" There's KFC on every street corner, or McDonald's, or fish and chip shops Bloody Domino's Pizza there with a great big fat juicy pizza in the window! You've got a newsagents that sells Mars bars and chocolates.
Subway - there you go.
Mo's facing a problem we all have - we're constantly bombarded with adverts for food.
But Mo seems particularly drawn to them, so we've asked our scientists to investigate why this might be more of a problem for our Constant Cravers than other people.
Geneticist Dr Giles Yeo has arranged an experiment here at a fun park in Southend.
He wants to explore the effects that hungry genes have on our volunteers' behaviour.
Could they actually biologically programme our Constant Cravers to notice food more? Mo's here, along with fellow Constant Craver Danielle but, crucially, for comparison, so are Nikki and Sara from our other dieting groups.
Giles, this is not quite what I was expecting.
I was expecting a genetics lab and we seem to be at a funfair.
Ah, we can run experiments everywhere.
So, the point is, I'd like to really test how you guys interact with the world and, in particular, what you look at.
And to do this, Giles has brought with him an unusual pair of specs - eye-tracking glasses.
These record every tiny movement our volunteers' eyes make as they scan the environment .
.
and so track precisely what they're looking at.
So I want you guys to put this on, wander around where your eyes will naturally actually go, OK for ten minutes, and we'll be able to see.
Giles asks everyone to take exactly the same route around the fun park.
# Oh, yes, I'm lookin' at the world Through rose-coloured glasses But he doesn't tell them the real goal of the experiment.
All around them, they see rides .
.
hordes of people and, of course, food - loads of food.
And to up the ante, Giles has added some extra snack vendors and food signs.
Yes, everything is rosy no-o-ow! The experiment's over and the data is extracted from the glasses.
Giles analyses the results to see if there's a difference between what each dieting group looked at.
So, Giles, put us out of our misery.
What was that all about - what are the results? As I understand it, you guys had eaten already, so you shouldn't have been hungry.
No! The important and interesting thing that we actually found was that the Constant Cravers, as a group - that's Danielle and, in particular, actually, Mo - you guys spent a whole lot of A vast amount of your time looking at food, and not just the quantity of food, but the variety of food.
We can't keep on living like this Mo and Danielle's eye-tracking data reveals EXACTLY what they focused on.
MUSIC: Temptation by Heaven 17 # All I desire Temptation # Keep climbing higher and higher Temptation # Adorable creatures Temptation # With unacceptable features Temptation Trouble is coming Without any instruction from Giles, Mo alone clocked a total of 16 hits on food.
Despite the dieters from the other groups having their own issues with food, they averaged just six glances each.
In fact, the Constant Cravers were drawn to DOUBLE the number of food items compared with everyone else.
Remember, none of them knew what Giles was looking for in the experiment.
It's confirmation that Mo and the Constant Cravers see the world differently.
Did you know you were doing that, Mo? Yes.
Surprisingly, actually, because, as I say, I wasn't hungry at all, and then as you're going round, there's hot dogs and there's ice cream and there's crisps and people stuffing their faces full of chips and burgers, et cetera, and you're just looking at everything.
OK, so it seems like so far, so good.
The test we did at the funfair seems to back up what we know about people like Constant Cravers, but why, what's going on? What is happening with the Constant Cravers is and what happens is you are hungrier than other people.
You may be 5% hungrier than the person next to you, but that 5% hunger adds up over your lifetime - it actually adds up.
So it is part of your brain controlling the food intake, and your brain is feeling hungry all the time.
Being permanently hungry gives our Constant Cravers a greater drive to search out food.
But HOW are their genes making this happen in the first place? For most people, when our fat stores are at a sufficient level, signals are sent to our brain to tell us we don't need to eat.
But scientists have discovered Constant Cravers have genes which disrupt the way these signals are received.
They trick our brains into thinking the fat stores continually need to be replenished.
The result - they want to eat the whole time.
This is what it's like to be a Constant Craver, the reality of living with hungry genes.
So what can Mo and Danielle actually do about it? So, guys, problems are evident everywhere.
When you walk through town, you see all these food cues - they're trying to sell you a burger, they're trying to sell you sweets.
A useful strategy might be to think, "These guys are trying to sell me a burger.
" You know, almost conceptualise that your problem is the food company that's trying to sell - which they are! It's easier to think, "OK, I'm fighting someone else's urges, someone else's plan "to make ME buy the food," than it is for you to fight your own urges.
Yeah, I can see that working.
It's achievable, easily achievable.
But, like you say, there's going to be a lot of thinking at first.
And what do you think, then, about the strategy, which I? I'm not saying that all companies are bad, but the strategy of actually blaming it on someone else's urging you to buy the food Like you said, it passes the burden, doesn't it, so the burden's not solely on you.
Being aware of the power of food advertising is a technique anyone can try, but will it work for Mo? After the funfair experiment, he's back on his rounds.
My biggest let down, if you like, when I do get tempted without thinking about it, is when I fill up with fuel, cos I'm out every day, all day, driving.
When confronted with a world of treats, he's going to imagine it's all a battle with food companies instead of his own cravings.
So here we go.
I'm going to pay for the petrol, I'm going to get in me car and I'm going to leave.
And here we go, soon as I walk in, it's all there, staring at me - big bars of chocolate, biscuits, and I'm not having it, no.
They've told me how to deal with this, I can deal with this.
I'm just going to pay.
How are you? I'm fine, thank you.
How's yourself, OK? Good, thank you.
Thanks, all the best.
Cheers, goodbye! And goodbye to you, cos I'm not buying No chance.
No, no, I can resist.
I don't want There's nothing here I need.
I need to go.
There's nothing I need.
The techniques that came from the funfair It was absolutely It was an eye-opener, it really was an eye-opener.
And I'd say, so far, it's about 7-3 to me.
It's hard, it's a hard slog.
Mentally, that is, but I am winning.
Of course, these are still very early days for Mo and the rest of our Constant Cravers.
Back at the nerve centre, the experts are keeping tabs on all of the dieters.
Weight-loss data is streaming in from the 75 volunteers in the three dieting groups.
And this is where the scientists are collecting it for analysis.
The next group are our Emotional Eaters, so-called because they turn to food in emotional situations.
At the start of our experiment, we identified this group using psychological questionnaires.
We also saw how stress, brought on by a fake driving test, made them eat much more than the other two groups.
You know, how I feel at minute, I just want to cry.
As a clinical psychologist, I've treated many people who have difficult relationships with food.
It can happen for any number of reasons - stress, anxiety, or depression.
But sometimes, it's caused by traumatic events.
And that's what happened to Alison Vaughan.
When I'm stressed, when I'm anxious, I'll use going to the kitchen cupboard or the fridge as a distraction.
Alison Vaughan.
APPLAUSE AND CHEERING If I was angry I would eat, and I'd eat lots, I would stuff, basically.
I would comfort-eat quite a lot.
I've yo-yo dieted since I was 15 and I'm 53 now, so time to stop and perhaps take some control.
Alison's story is particularly harrowing.
Her problematic relationship with food started as a child.
My relationship with food Mmm.
It's been quite negative in the past.
And where that comes from That's as a result of being deliberately deprived of food when I was very small.
Alison was abused when she was younger.
She was starved of food, and bread and water was used as punishment at mealtimes.
If I'd been naughty, I wouldn't be allowed to run round the house with the other children.
I would have been in bed.
And then (It's OK, I'm not there now.
It's all right.
) And then I'd be called downstairs, and sat at this table.
And the table had a drawer in it, I remember.
And I'd be presented with this In fact, it'd be more soggy than that.
That's it - it would be well soaked.
And I'd be given that and I'd be given a spoon, and it'd be this size spoon.
And I'd be told that that was what I'd got to eat for my tea.
I think that's at the core, that's what kick-started things off in terms of food.
Nearly 50 years have since passed, and Alison is now happy.
She's married with a family.
But her troubled relationship with food remains, and she's hoping that science can help.
I feel quite relieved about being classified as an emotional eater, becauseit kind of gives you a footing from which to continue.
Because unless you can see what the issue is, you've really not got any hope of changing.
Alison's experience is extreme amongst our emotional eaters, but it can tell us something more general about why they all eat too much.
Our scientists are keen to discover what happens in their brain that compels them to comfort-eat.
'Alison and I have arranged 'to meet up at a research centre in Cambridge.
' Hello.
I'd just like to introduce you to Alison.
Hi, I'm Hisham.
'Neuroscientist Dr Hisham Ziauddeen is going to analyse Alison's brain 'when she's presented with food.
'To do this, he's going to use an fMRI scanner.
' How do you feel, are you all right? You're not claustrophobic, are you? No.
Well, I'll see you on the other side then.
Good luck, see you later! 'While she's being scanned, 'Alison's told she's about to be given something she likes.
'A chocolate milkshake - fed into her mouth by a tube.
' 'Two seconds before Alison receives the milkshake, 'the letter A appears on the screen in front of her.
'It means Alison can anticipate it before she actually tastes it.
' You'll then receive a little chocolate milkshake when there's a "taste" red flag up on the screen.
That OK? Yep.
'Hisham's focusing on one key region of Alison's brain.
The bit that we're interested in is actually plum here in the centre at the bottom.
And why we're interested in that area is that's where a lot of the brain's reward circuitry is based.
Food is obviously one of the most common biological rewards we encounter, but it's the same area of the brain that actually responds to other kinds of reward - be they money, be they drugs, be they sex.
It's telling you something coming in, or something out there, is pleasurable.
It also is doing the computations that allow you to act upon that pleasure - "Do I want to go and get it?" The activity in this area of the brain just before Alison gets the milkshake tells Hisham how much she desires it.
Alison is in a good mood for these first scans.
But for the next stage, Hisham wants her in a very different state of mind.
He's going to use a tried and tested psychological technique to induce a depressed mood.
You may feel a little down, but that's the whole idea of this session.
Alison's played sad music MUSIC: Adagio in G minor by Tomaso Albinoni .
.
and made to read statements known to make people feel low.
MUSIC CONTINUES And in this mental state, she's again told to anticipate more milkshake.
The scans are complete, and Hisham's experiment is over.
Welcome back! I was crying in there.
Were you crying? Yeah.
Oh, no! So, are you all right now? Yeah, yeah, yeah.
'Clearly Alison felt sad, 'but what difference did it make to how her brain responded to food?' Alison, what we have here are a set of images of your brain from when you were lying in the scanner.
'In a good mood, 'Alison's brain activity increased in various places - 'including the all-important reward circuit.
' 'The greater the activity, the brighter the colours appear.
'Red is a low score, orange and yellow are higher, 'and white is the highest.
' So this is actually fairly typical of what you'd expect in most people's brains if we were presenting them with something that they liked, like a chocolate milkshake.
What I'm going to show you next is what happened after we did the mood induction, when you were feeling quite down and, again, we're going to look at your brain's anticipatory response when you were waiting for the milkshake to come with just the A on the screen.
'The reward circuit in her sad mood looks different.
' 'It glows bright white.
' 'Far more intense than when Alison was in a good mood.
' Wow! Gosh.
In that negative mood, the value of that particular milkshake that you were about to get was much higher.
That explains why, when I get upset, I'm straight to the cupboard - biscuits.
It's fascinating, isn't it? The big change we saw was in the anticipation.
It was.
Quite extraordinary.
'All our emotional eaters desire food more 'when they feel low, sad, stressed or angry.
' 'At those times, the kind of reaction we saw in Alison 'is very likely to be happening in their brains too.
' So, that was quite a revelatory experience.
Amazing.
I now know my own brain works against me, actually.
That's pretty much it, Hisham, is that right? There's a part of your brain that's conditioned to respond that way to food, and it has been doing that for years.
'Our scientists gave the emotional eaters a dieting plan 'that targets their particular problem with food.
' 'One part of this is group support.
'This uses the encouragement of others 'to help stop you turning to food when you're down.
' 'To get that support, 'our emotional eaters are all attending dieting clubs.
' Four and a half pounds off, Alison, well done.
Our scientists have also advised the emotional eaters to support each other online.
And they've recommended cognitive behavioural therapy, which helps them manage the thoughts, feelings and behaviours associated with comfort-eating.
To discover more about this kind of therapy - and the dieting strategies for all three groups in our ambitious diet experiment, head to: And if you're curious about what kind of eater you may be, go to the website and use our diet calculator to find out.
Back at the nerve centre, our scientists are busy keeping up with all our dieting groups.
So far, they've checked in with the constant cravers, and the emotional eaters.
The third and final group are the feasters.
Our feasters tend to overeat at mealtimes - once they start, they can't stop.
And that's because they just don't feel full.
In the assessments at the very start of our experiment, the scientists tested our volunteers' levels of one particular gut hormone.
At mealtimes, this hormone tells your body when you've eaten enough.
But we discovered our feasters produce much less of this.
This means the food they eat doesn't make them feel as full.
In the last episode, our scientists put on a never-ending sushi banquet but none of our volunteers knew it was actually a test.
Well, I've been watching Heidi, who has managed to power her way through about 12 dishes so far.
The feasters ate a LOT more than the other two groups.
And, in total, Heidi Locke polished off 15 plates.
That's over 2,000 calories even before the wine.
To the future! Yes.
Now, Heidi's back at work as an air hostess.
She's trying to stick to the diet our scientists gave feasters like her.
When I was told that I was a feaster and the reasoning and the science behind it, kind of a light bulb went on, you know? It makes sense now that I'm not producing enough of this gut hormone to tell myself to stop.
You know, "Stop eating, Heidi!" "No!" It's kind of nice to know that it's not just me - there's an actual physiological reason behind it.
Thinking that I have to tell myself to stop eating, my brain's not going to do it, and that's something that's a new tool in the box, if you will.
The diet we've given the feasters is designed to boost the feeling of fullness from meals.
Lots of protein and, also, foods with a low Glycaemic Index, or low GI.
These take a longer time to be processed by the gut.
So, what would the ideal meal for a feaster look like? A quarter would be lean protein, like chicken or fish.
A quarter low GI carbohydrates, like pasta or basmati rice.
And the remaining half? Vegetables.
For desserts and snacks, the feasters should stick to fruit.
This diet requires you to eat like this every day.
But it's just two weeks in, and Heidi's already finding it tough.
I didn't anticipate in any way, shape, or form, how hard it would be, and how difficult it would be to continually try to stick to it.
For Heidi, fruit and veg are no substitute for her favourite foods - pastries and cakes.
They have my favourites - I mean, they have the Bakewell slice, they have the cherry pie and my apple strudel.
Normally, I'd just be popping in there for something nice but, no, I'm just going to go for the fruit today.
The challenge Heidi faces is common to all our feasters.
If you're really fond of sugary and fatty foods, then suddenly changing your diet can be really difficult.
And what's even harder is substituting fruit and veg in place of those foods.
That's particularly true with veg.
So our scientists are hoping to discover if there's a way to get all the benefits of fresh vegetables, only without it seeming like a chore.
They're inviting all the feasters back to the diet lab to run some tests.
They want to know what happens inside the feasters' bodies after they eat either a plate of cooked veg or that same veg blitzed up with water into a soup.
Professor Fiona Gribble wants to see what's going on inside the feasters' stomachs, and she's going to use ultrasound.
First up - whole veg.
I'll be honest, ultrasound always looks like a badly-tuned telly to me.
What are we looking at here? You had chickpeas.
And what you can see here is the solid food within the stomach, which are these white areas here and very little in the way of gas, so the stomach is actually full with the food, and it's holding it there.
'Now, that's what you'd usually expect.
'Veg typically remains in the stomach for a couple of hours 'whilst it's being digested, 'and that actually helps our feasters feel full.
' Nice.
Now we know what a chickpea looks like on an ultrasound scan.
Or 100 of them! LAUGHTER Gut hormones aren't the only way we feel full when we eat.
There's another mechanism.
Our stomachs are lined with thousands of nerves.
They send signals to the brain about how full or empty the stomach is.
Bulky food like veg really stretches the stomach, stimulating those nerves.
That makes it filling, even for our feasters.
The food is still sitting in the stomach - the stomach will be having to work on that to break it down, to mix it with enzymes, break it down into small pieces before it will let it out of your stomach.
So while it's there, it should actually be stretching your stomach and sending signals back to your brain to say, "My stomach is full, it's still got this food in it, "don't eat any more.
" But there's a problem.
Many of the feasters don't enjoy this sort of food.
Not something I'd choose for a meal.
I didn't really enjoy it, obviously.
I couldn't eat any more.
So, what about the soup? Won't it just pass right through their stomachs, and not fill them up? I'm feeling like I'm pretty full.
I do feel quite full from just a small bit of soup, which is quite good.
That's really satisfied my appetite, that.
I'd like to know the recipe.
It seems as though the soup is making the feasters feel full, and Fiona knows why.
She's prepared a glass model of the stomach to help reveal how the soup can be just as filling as the veg.
The oesophagus drains food into it, and out of it you have an opening that goes into the intestines.
So, here's soup going into the stomach.
OK, so the soup is trickling through, but slowly.
That's right.
It's very well established that a thicker solution in the stomach will actually hold these food contents in the stomach for longer just because the nature is such that the food can't empty so quickly through this narrow gap, so that will give this greater sensation of fullness.
Thick soup stretches the stomach and, crucially, stays there for a long time.
That's why, in scientific tests, soup has sometimes been shown to fill you up even more than solid veg.
This is what makes it a handy dieting tool .
.
especially for our feasters.
Our experiment is now well under way.
Regular video diaries from our dieters continue to pour in and nutritionalist Professor Susan Jebb is monitoring them from the nerve centre.
Everything's been superb.
Everything's gone brilliant.
Weighed myself on Saturday and I've lost approximately half a stone.
I've lost five pounds, which I'm over the moon at, because that takes me down to the next stone, so that makes you feel as if you're heading in the right direction.
Well, this is my second full week at Slimming World, just got back.
I've lost two and a half pounds this week, which I'm delighted with.
I've had to do my trousers up with an elastic band because, when I put my phone in my pocket, they fall down.
I have lost somewhere in the region of a stone.
I'm absolutely blown away by that.
That's mind-boggling to me.
I'm so delighted.
Well chuffed with myself.
That's a lot of very happy dieters.
It's a really good start and, as we can see here, the rate of weight loss in each of the three groups is pretty similar.
And what is the rate of weight loss on average? We were hoping that people would lose about two pounds a week.
In fact, on average, they're losing three pounds a week and, as we've heard, some people are losing much more than that.
'It sounds like fantastic news, 'but our dieters are about to get a cruel surprise.
'A substantial amount of that weight loss isn't actually fat.
' We know that people tend to lose weight more rapidly in the early weeks of the diet, and some of that is just a little bit of water loss.
So, we lose water at the beginning of a diet.
How much, in general, are we going to lose in those early weeks? Well, certainly a pound, maybe even two or three, but, by the end of the first week, it's probably mostly over.
The reason that water loss happens at the start of a diet is that, while the body begins to burn fat, it's also using up another temporary energy store - sugars stored in your liver and muscles.
All this sugar is kept in a solution with water.
For every one gram of sugar, there are about three grams of water and, when the sugar goes, your body loses that water too.
In some people, this can account for more than two pounds of weight loss.
Regardless of the diet we're on, most of us lose weight quickly at the start, but that inevitably slows down and progress begins to feel much harder.
So what can we do at this stage? Well, some of our dieters, from all three groups, have decided to try something they wouldn't normally do.
Exercise.
Whether it's classes at the gym, roller-skating, or swimming, time and again, it's the one thing recommended to go alongside a diet.
The popular belief is that exercise automatically helps you lose weight, but there's a catch.
In principle, weight loss should be pretty straightforward.
We just have to make sure we use up more calories than we eat.
So, on that basis, for our dieters, exercise should increase the amount of weight that they lose, but is it really that simple? We've called on a leading scientist in exercise, Dr Jason Gill from the University of Glasgow.
Until now, each experiment has targeted just one of our three groups, but all our dieting groups are exercising, so we've got a mix here today.
Brian, Derek, Susan, Nicola and Kirsty.
So what we're going to do is try to work out whether exercise can help us with weight loss.
So, to do that, we're going to get you to wear these devices, which are called accelerometers and they measure all your body's movements.
So I'm going to ask you to just tape it on to your thigh and leave it there for a week.
'Once fitted, the devices start monitoring their activity levels 'by counting the number of steps they take.
' So the more you move, the more calories you burn.
So all I want you to do is just wear these accelerometers for the next week and just carry on doing your normal daily activities, don't change anything.
For the first seven days, our five dieters are living life as normal with no additional exercise.
This gives Jason a measure of how much activity they do in a normal week.
It's their baseline.
But, for the second seven days, he's shaking things up a bit with a personal trainer who is going to put our dieters through hell.
Hold it! Ten, nine, eight, seven, six, five, four, four, three, two, one, up you come, well done.
Shake out the legs a little bit.
OK, we're going to go down.
Big strong push through the heel.
Try to work on your bum.
Jason wants to see what intensive exercise does to their bodies.
Lean back.
First two, you're off and away.
Oh, go you! Go you! Dynamo! Slow and controlled.
Bring the hand up.
Good.
Keep the bum down.
Keep the weight pushed forwards from your hips to your toes.
In just one week, our dieters endure three exercise sessions.
Can I just stay here and you just come back for me in the morning? Our volunteers don't know it, but this experiment isn't just about what they're doing in these sessions.
They'll keep wearing the accelerometers when they're back at home too.
What we're very interested in is the effect of this exercise session on their activities over the rest of the day and over the rest of the week.
Finally, the accelerometers are removed and Jason extracts the data.
Everyone's activity levels have been totalled up.
In the first week, without exercise, the group averaged 8,000 steps per day, but in the second week, on the three days they exercised, they averaged far more - over 11,000 steps.
So, that can be difficult to visualise, but we can visualise it in the form of a universal energy currency of swiss roll.
How much of the swiss roll do you think you burnt in your exercise sessions? One bit.
One bit.
OK, so A third of it.
A third.
So, we've got between a slice and a third.
You actually burnt off all of it.
Wow.
It's a good visualisation, isn't it? Are you pleased? Absolutely, yeah.
'Over the three days of exercise, 'each dieter burnt off the calorie equivalent of this much swiss roll.
'It seems impressive, 'but Jason's got bad news too.
' But there is a "but" here.
Yes, we measured what you did on the days when you did the planned exercise sessions, but we also measured what you did on the days when you didn't do the exercise sessions, and the graph looks something like this.
Here's the twist.
On the four other days, the ones when they weren't exercising, their general activity levels plummeted.
In fact, they did over 1,000 steps fewer than they normally would.
You look really surprised.
That surprised me, because I felt, after the exercise, I was really motivated and I got a real buzz off it, so I thought, the next day, I would be more empowered to do more, so that's really shocked me.
It's a well-known phenomenon.
So, what happens is you do your exercise and then, in the time when you're not exercising, you might actually do a little bit less activity than you would have done otherwise.
You think you've earnt a reward.
But there's a term for this, isn't there? Yeah, it's called compensation.
Compensation hits many of us after we exercise.
Either consciously or subconsciously, we rest up more than we normally would.
This can take a big slice off the total number of calories we use up over the week.
So, if we take this sort of whole swiss roll that you burnt in the sessions, you guys, with your compensation, actually lost about a third of it.
That goes away.
Oh! Oh.
That's still pretty good, but it's a third less because you're compensated.
Fortunately, Jason has a solution.
It's a little device called a pedometer and it lets our dieters see exactly how many steps they're doing every day.
They're not very expensive.
They're about £20.
So, what they do is they give you feedback and so, by giving you feedback, you have to sort of work to a goal and you can see whether you're achieving that goal.
You want to keep your steps up to your target and that stops you from doing the compensation and reducing the activity outside the planned activities.
And the idea is to build to a step number that's 3,000-4,000 per day more than you started off with.
Here's the truth about exercising while you diet.
You need to be really careful not to slob out on non-exercise days and, while exercise is really good for your overall health, the most effective way to lose weight will almost always be to change your diet.
It's nearly a month since the start of the experiment and, in all three groups, things are getting even tougher for our volunteers.
A bit of a harder day today for some reason.
It's the first day erm, that I've wanted things.
My weight loss seems to have ground to a halt this last week, which is a bit frustrating.
I must admit that it is frustrating, because I'm starting to starve, or I think I'm starving myself and not losing any weight at the moment.
I don't know why that is, but we'll have to wait and see.
Well, I went to slimming club last night and I've put on half a pound.
Gutted.
I've just had a A disastrous weekend, a disastrous week.
I just don't want to do this any more.
I want to lose weight and I want to lose it now.
My next-door neighbour has fish and chips and it's actually seeping through the walls and I can smell it.
So what's going on? Because we saw them two weeks ago and they were just full of life, loving it, no-one was complaining and they were all losing weight? Well, if we look at our group total weight loss here, what you can see is that the rate of weight loss really has started to slow down after that very successful first week.
So they lost masses there, and then much less over this period of time.
Yeah, and that's obviously pretty demoralising for people.
Losing weight requires real effort and mental energy, and that in itself is quite tiring.
Now that the honeymoon period is over, they're really reaching the point where it's getting hard to work up the energy and the motivation.
This tiredness, the mental fatigue you're talking about, that can't be helpful.
This is an incredibly risky time because there's a danger we get into a vicious cycle.
So, then, of course, they find it even harder to lose weight, they get more fatigued or tired and then the problem continues.
You're absolutely right.
It's a scary thought.
Tiredness in itself can lead to a diet failing.
And to investigate just how much tiredness can affect our ability to make good food choices, Susan's arranged a trip to the shops for our volunteers.
The thing is, there are so many temptations in life that can lead us away from healthy decision-making, but how can our state of mind impact on our ability to make those healthy decisions? A supermarket is a surprisingly dangerous place for our volunteers.
It's incredibly important, if you're going to stick to your eating plan, that you make the right choices whilst you're shopping.
Here you've got a choice of, you know, 20,000 or 30,000 different foods to choose from.
Once you're in your kitchen, you're stuck with the choices you've already made, so it's really important to get it right here.
Our experts think that, because of their psychology, the emotional eaters might be particularly vulnerable to the effects of tiredness.
So Susan has recruited ten of them for an experiment.
She's going to test the effects of exhaustion on the food they choose to buy.
First, she needs to mess with their sleep.
Five of them are going to bed early, while the rest have to keep each other entertained late into the night.
Swimming! It's currently 12:30.
We have to now stay up until three.
Shark.
Whale.
Godzilla.
Forgive me if I'm a bit cranky in the morning.
I do apologise.
Our five sleep-deprived dieters only get three hours' kip, so what difference will this make? The well-rested emotional eaters turn up at the supermarket bright-eyed and bushy-tailed.
The sleep-deprived team are rather more subdued.
Good morning, everybody.
So nice to see you.
You have slept all night, yes? Yes.
You haven't slept very much at all? So, you need to know why we're at the supermarket.
So, Susan, why don't you explain? So we want to do a shopping task for us.
I'm going to give you a list, £25 and just 20 minutes to go and do your shopping.
OK, are you up for the challenge? ALL: Yes.
It's like a game show, right? 'Both teams have just 20 minutes 'to buy four different categories of food.
' Oh, fish.
'A breakfast cereal' Oh, that's a bloody bargain, that.
£1.
99.
'.
.
a ready meal' Anybody can run.
'.
.
dinner for four' Pizza, garlic bread, mayonnaise.
'.
.
with drinks' Include drinks.
I need my drinks.
That'll do nicely.
'.
.
and a snack that they want to eat right there and then.
' 'Of course, none of our dieters know what Susan is hoping to discover.
' Both teams finish and the food is laid out.
And it's immediately obvious that the tired group have made different choices to the rested group.
I'm sorry, I feel like we've tortured you here, in the name of science, but are you seeing differences in the tables? Yeah, their table looks a lot healthier compared to ours.
There's cake on our table.
There's a lot of cake on your table.
There's a stack of cake on your table.
Yeah.
Chantelle, did you make any specific choices shopping when tired? I did get a specific brand of pork pies because I was whizzing past and I thought, "Oh, I've just got to have them.
" What? Now? Yeah.
Right that second.
And why did you have to have them right that second? Because they're just really fatty and just really yummy, and fatty food's just good when you're tired and exhausted.
So, it's clear to everyone that there are some differences.
Susan's analysed everyone's shopping and the nutritional content starts to reveal the true extent of the problem for our tired shoppers.
There are two and a half times as much sugar in these breakfast cereals as our sleepers had in their choice of breakfast cereals.
So, we asked you to choose a ready meal.
When we look at what you've chosen, you might be surprised to hear that you've chosen more than three times as much saturated fat as you're well-rested colleagues over here.
But the biggest shock is when Susan compares everything the well-rested dieters bought to what the tired group bought.
This table over here, I can tell you that you're shopping today is about 37,000 calories.
That might seem a lot, but let me tell you that this table managed a staggering 61,000 calories.
That's more than one and a half times as many calories.
It might seem obvious that being tired can lead to a few poor choices, but Susan's experiment shows it's actually a dieting catastrophe.
Tiredness messes with your decision-making, increasing your desire for foods high in sugar and fat.
Yummy.
The reality of most people's lives is that they are time-starved.
Most of us are completely exhausted when we go shopping, so how can we avoid this, then? How can we make it different? Well, recognising that that's going to happen is really important, because if you know you're going to be caught out in the shop when you're tired, you can prepare for that in advance.
So if you know you're going to be going to do your big shop on the way home from work, then make a list the night before or the morning before, sometime when you're feeling fresh.
Make a plan, make a list, take it with you and stick to it.
If you do that whilst you're losing weight, then, over time, you will develop those new healthy habits and you will be able to just breeze in to the supermarket and make good choices.
We're bringing everyone back to our diet lab in Liverpool for their one-month weigh-in.
Yay! Hello! How are you? I hope you know I was married.
He ain't now! At the very start of the experiment, we set them the goal of losing more than 5% of their body weight in just three months through personalised dieting.
Other studies show that this is a tough target to reach.
Today, we're going to find out how they're getting on so far.
Good morning, everyone.
It's great to see you all back.
Now, you've been dieting for one month out of the three, so it's time for a checkup, and we want to find out how the diets are actually going for each of you.
The feasters have been following the fullness diet - rich in protein and low-GI foods.
What were you before, when we started? When we started I was 18.
9.
18.
1.
8 lbs.
8 lbs.
Yeah, I think that's fabulous.
I think that's fabulous.
The emotional eaters have been following the diet plan based on group support and using cognitive behavioural therapy.
So, you were before 17.
2.
And that says, now, 16.
8.
Yeah.
I'm very pleased with that 8 lbs.
You couldn't get into this dress before, could you? No, no.
This is an old dress that got too tight on you - and now look at you, you look great in it.
It's so nice.
'Finally, the constant cravers.
'They've been following the intermittent fasting diet.
' 22.
11.
What were you before, Brian? 24.
8.
So, you've lost almost 2st.
Far, far better than I expected.
It's the first diet I've ever done that I know I can stick to and I will stick to, and I can see it really long-term.
But not everyone is as pleased.
Let's have a look.
God, it's awful.
It's not even OK, what sort of loss is that? About 6 lbs.
No more than that.
And how are you about that? Not great.
I mean, I am a craver, I am a constant craver, so I am always thinking about food, day and night.
Admittedly, I'm honest, I haven't worked as hard as I should, I'm not going to deny it.
6 lbs in four weeks.
That's not bad.
That's healthy, that's slow, but that's steady.
It's slow, yeah.
Please don't think you've failed or you haven't worked hard enough.
You've done what you've done, now we kick up to the next gear.
Yeah.
Move up.
'So, that's individuals, 'but now we'll see how the whole group has fared overall 'and what progress they have made towards that target of 5%.
' OK, everybody, the numbers are in and, since our first weigh-in, you as a group have now lost in total 53st! That's amazing! Extraordinary! And, of course, as individuals, what that means is you've lost, each, on average, 4% of your body weight.
But, listen, the honeymoon period is over.
You're going to have to steel yourselves for the next couple of months.
You've got your targets, we know you can get there, but it is going to be tough.
What happens now is about whether or not you can turn what you've accomplished recently into long-term change.
So, good luck, everybody, and well done.
Well done.
If you want to see if you match up with one of our groups, head to .
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and use our diet calculator.
Discover which diet might suit you, your family or friends, and get more weight-loss tips.
Next time on What's The Right Diet For You?, our scientists bust the myths about metabolism, reveal the secrets of our most successful dieters That's a 25-kilo sack of chicken feed and that's just about what I've lost in weight.
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and discover how to keep weight off for ever.
It's going to give hope to millions of people out there who have dieted and failed in the past.