We're 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 volunteers...
and divided them into three groups, based on their genes,
their hormones and their psychological profiles.
Our groups have been put on different diets according to
what makes them overeat.
After the first month,
volunteers were well on the way to their weight loss goals.
You, as a group, have now lost,
in total, 53st!
CHEERING AND APPLAUSE
That's amazing.
But, as we near the end of the experiment,
it's starting to get more difficult.
Now, for many, the honeymoon period is over - it's getting harder
and harder to lose weight as their minds and bodies fight back.
This time, we find out
if the new personalised diets will help them stay on course.
And our experts reveal the scientific secrets to
permanent dieting success.
Three quarters of successful dieters have one thing in common, OK?
And they actually have breakfast.
We find out how small changes to your lifestyle can make a big
difference.
We're not walking very fast, we're strolling along,
and he's at about six, six-and-a-half calories per minute.
Just walking along.
And how you get back on track when you break a diet.
Boy, did you blow it, you ate eight times as much cake as these guys.
LAUGHTER
Oops.
We're now at the final stage of our diet experiment
and it's getting really tough.
So what can our volunteers do to keep off the weight for good?
'I'm Dr Chris van Tulleken, a medical doctor
'and a research scientist.'
'And I'm Professor Tanya Byron, a clinical psychologist.
'I often work with people with eating disorders.'
And 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.
So this series is about discovering the individual causes for
overeating, and the answer could lead each of us to the perfect diet.
So far the scientists have put our 75 volunteers through
a series of tests at our diet lab, here at Liverpool Hope University.
They've split them into three groups, based on why they eat too much.
The first group are the constant cravers.
They've got a greater number of what our scientists are calling hungry
genes, and these genes give them a higher drive to eat every day.
I can eat constantly every ten minutes, all through the day.
I could put a sausage roll in my mouth.
Next up, our emotional eaters.
This group were found to use food to manage their emotional state.
Something happens and I run for the biscuit barrel.
And finally, we have our feasters.
And they've got a specific problem.
Once they start eating, they can't stop.
They produce less of a hormone that tells them when they're full.
Sometimes I would actually order a takeaway, even
after having an evening meal.
Each group has been put on a diet that targets the main
cause of their overeating.
For two months they've been following these personalised diets.
There's just four weeks left until the end of the experiment.
At our nerve centre, nutrition scientist, Professor Susan Jebb,
is analysing the recent progress of our volunteers.
They've been sending in reports of how they're getting on.
Found it a bit hard this week,
I've not lost any weight as yet, It's Friday.
I was hoping to have lost at least a pound or so.
You could've knocked me down with a minuscule feather when I realised
I'd actually gained 2.5 lbs.
I know I haven't cheated, I know I've stuck to the regime.
Very disappointed. The scales are showing 174.6, which is
a gain of 2 lbs.
I've stuck to the diet, diet, so I'm very disappointed.
I'm going to have to make some enquiries as to what's gone
wrong there.
That's really interesting. Everyone's saying very much the same thing.
Why isn't this getting easier to stick to as they go along?
It's really still too early for them
to have established those solid, healthy eating habits.
They're at the stage where it's still really hard.
So now they're complaining they're not losing weight, or
they're even gaining weight. Is that normal?
It's certainly very common. We often see that people have
that initial early, quite rapid weight loss, then it slows down.
And most people will often find themselves
moving into a complete plateau when their weight's totally stable.
One of the constant cravers, Morgan Missoum,
has lost just over a stone so far.
But in recent weeks his weight loss has started to level off.
When everything slowed down, you slow down, too, in your head.
"Why am I doing that for?"
Now my question is how I am going to be able to speed that up.
What's going to bring me to the next step?
We're here with Morgan, we can see his graph has plateaued.
Is there some way of finding out what's going on with their bodies?
Yes. There's certainly an element of biology about this.
There are physiological processes, which are beginning to kick in
and trying to maintain the body's weight effectively.
In our diet lab's Great Hall, we're going to test Morgan
and his fellow dieters, to see what's causing their biological backlash.
Just cross your arms.
You comfy?
Susan wants to look at a specific biological
process that could be slowing down their weight loss.
And it involves breathing into these strange-looking hoods.
OK, so we've got everyone in the room looking like we're
about to send them all to Mars. What exactly are we doing here?
Well, many of our dieters are experiencing that plateau
when they're finding it hard to lose weight and that's partly
because their body's beginning to fight back,
so what we're doing is measuring their metabolic rate.
Our metabolism breaks down food and changes it into energy.
The speed at which your body does this is called your metabolic rate.
It's a measure of how fast we burn calories.
Our metabolic rate is influenced by lots of factors, such as age,
gender and size.
So at the start of the experiment, we measured everyone's metabolic
rate, and what I want to do today is see just how that's
changed as a result of the weight that they've lost.
I've heard a lot of people say that their excess weight is
because they've got a slow metabolism.
Is that true?
That's not really the case at all. In fact, quite the contrary.
What we know is that bigger people actually have a higher metabolic
rate. That's because they've got a bigger heart, lungs, their muscles
are bigger. It takes more calories just to keep their body ticking over.
It's rather like a big car uses up more fuel than a smaller car.
Really? So I think that's very counter intuitive. I think
most people would assume that slim people have a higher metabolism
but that's not the case.
No, that's one of the great myths of dieting.
'Today, Susan is measuring the dieters' resting metabolic rate.
'That's the amount of energy it takes to run their bodies while at rest.
'It will tell her the number of calories they use
'just to carry out basic functions, like breathing and circulation.'
OK, so we've got Morgan plugged into the machine.
We're getting live data through the tube.
What am I looking at?
What this is telling us is how many calories Morgan is
burning off just lying here completely at rest, so we're measuring,
minute by minute, his energy expenditure. And this is calories
per day. So he's... It looks like on average he's a little bit over 2,000.
What was he when we measured this before?
That's the remarkable thing because
when we first measured, at the start of the experiment, he was using a
couple of hundred calories more than this because he was a bit heavier.
So Morgan's body now uses 200 calories a day
less than it did at the start of the diet
eight weeks ago.
Oh, Morgan, well done, that's great. How are you?
After 30 minutes under the hoods, it's time to see what's happened
to the whole groups' metabolic rate compared with two months ago.
So this was the measurement at the start,
and this is the measurement we've made today.
On average, metabolic rate has gone down by about 5%.
So their metabolic rate has slowed down.
That's absolutely right.
But remember, all of our dieters have lost weight.
They're smaller people now, they've got less body mass to support.
OK, so that's' great in some ways, but of course it's going to
make it harder for them to lose weight. Absolutely. And
so it's this decline in metabolic rate which is part of the reason why
it gets harder to lose weight over time, and some people even experience
a plateau. If you're going to keep up your rate of weight loss,
you're going to have to make permanent changes to your eating habits.
That's a bit of a bombshell.
As you lose weight, your metabolic rate goes down.
So if you want to keep losing weight at the same rate,
you have to eat less as your diet goes on.
The metabolic rate hurdle applies to all of our groups.
This stage of a diet is hard for everyone.
But our experts have come up with a series of ways to
help our groups keep their weight loss on track.
So we're starting to get a sense of why it's
so hard to stick to a diet as weeks turn to months.
But for one of our groups, there's another reason why keeping the weight
off is going to be a big challenge, and that's because for this group
the desire to eat large quantities of food is simply enormous.
Our feasters tend to overeat at meal-times.
They produce less of a hormone that tells them when they're full.
For most of us, when food arrives in our intestines,
hormones are released.
These hormones are chemical signals.
They travel through the blood and reach the brain.
This is how they tell us
when we've had enough food and should stop eating.
But people in our feasters group produce less of these gut hormones.
In particular, one called GLP-1.
It means the signal that tells them to stop eating is weaker.
Our scientists have put our feasters on a high protein, low GI diet.
Low GI stands for low Glycaemic Index,
These foods are digested slowly.
That means meat, beans, lentils,
lots of fantastic grains and cereals.
This makes them feel fuller quicker and for longer.
Feaster Bob Marchant manages a B&B with his wife in Yorkshire
and he's constantly faced with fry-ups every morning.
When they split us into groups and they told me I was a Feaster,
I was not surprised.
Because I really can eat and eat and eat
and my brain doesn't get the message that I'm full.
Stupidly, I didn't relate the fact that I'd just had a meal
to not allowing me to have a piece of cake
or a biscuit with a cup of tea afterwards.
I just don't feel full.
At the beginning of the experiment, Bob was 23 stone.
By eating foods that make him feel fuller,
he's managed to lose two stone in two months.
In here, I've got a whole section of stuff
that has become my Feaster's shelf.
So we've got cannellini beans, borlotti beans,
black turtle beans,
bulgur wheat, green lentils, quinoa.
But his wife thinks Bob's eating habits have room for improvement.
If I was still eating mine and I had some chips on my plate,
but Bob had finished, he'd eat my chips before I'd finished eating.
I would say he eats fast
and he just continues to eat.
He doesn't stop.
Bob eventually wants to lose another two stone,
so he still has a way to go to reach his weight-loss target.
Our Feasters are now thinking about
how they can keep off weight in the long term.
And there may be a way to help them
that's got less to do with what they eat
and much more to do with how fast they eat it.
Gut-hormone specialist, Professor Fiona Gribble,
has brought the Feasters to a fast-food van to set them a test.
So today's experiment is to look at how fast people eat
and what effect this has on people's gut-hormone levels.
And why are we interested in how fast people eat?
Well, there's evidence to show that people who eat too fast
tend also to eat too much.
And not only that, but fast eaters
tend also to be the people who are overweight.
Fiona's going to get our Feasters to eat a fast-food classic, a burger.
We're telling them we're testing the effect
the burger has on their gut-hormone levels.
But this is only half the story.
What we're not telling them
is that what we're really interested in is how fast they eat it.
OK, everyone, we've equipped you with one burger each,
you're standing in a field,
Fiona, explain to them what we're up to.
So what we want to do is
to measure the effect of this takeaway on your gut-hormone levels.
But there are some rules.
So you have to finish the burger,
we don't want any talking
and because we're measuring the hormone levels,
we need you all to start at exactly the same time, OK?
So in three, two, one, eat.
Why have we got them standing up?
Well, the reason we've got them standing up is
because if you're standing up, you have nowhere else to put your food,
you tend to eat faster. Right.
Our Feasters know we're filming them.
But what they don't know is that Fiona has a team of scientists
secretly timing how fast they eat the burger.
Looks like Mike is about to finish, isn't he?
And we're about two-and-a-half minutes in.
That's a very fast rate to eat over 500 calories.
Bob and Alistair are about to finish
and we must be now about four minutes.
The whole group are looking as if they're coming towards the end now.
Time to reveal what we've been up to.
What we're interested in is, we are going to measure the gut hormones,
but we want to know how fast you ate the burgers.
THEY LAUGH
So, who was first to finish?
Mike, you were. Mike, do you know how fast you ate the burger?
It was just over two-and-a-half minutes.
How did you feel immediately after you'd finished it?
Like I wanted another one.
You'd have quite liked another one? Yeah, easily.
You're not getting another one. THEY LAUGH
Bob and Alistair, you guys were next quickest at just under four minutes.
Do you normally eat takeaway food that quickly?
Do you consider yourselves fast eaters?
Certainly, if I'm sat around a dinner table,
my plate's empty before most other people's, yeah.
Really? Yeah, absolutely.
On average, our Feasters ate their burgers in under five minutes.
Fiona and her team are taking blood samples
so that they can see what effect eating quickly
has had on the levels of the fullness hormone, GLP1.
The next day, our burger van is open for business again.
Fiona wants our Feasters to eat the exact same meal,
but today, they must eat their burger sitting down
and in a slow 30 minutes.
So if everyone's ready, I'm going to count you down.
Three, two, one, eat.
Slowly.
THEY LAUGH
Fiona, have you got tips for everyone while they're eating
about how to eat slowly?
Because I don't find it easy.
You can chop up your food,
put your knife and fork down between mouthfuls.
You can have a glass of water
and you can take a sip of water between mouthfuls.
You could try using chopsticks,
particularly if you're not very good at using chopsticks.
That would really slow you down eating a burger, wouldn't it?
It would slow me down, eating a burger with chopsticks!
OK, so we're coming right up to the end. 10 seconds left.
Let me give you the countdown. Ten, nine...
THEY LAUGH
..two, one.
Once again, Fiona and her team take blood samples.
This time, they want to see what's happened
to the levels of the Feasters' fullness hormone
when they've eaten slowly.
Back at the diet lab, Fiona has pulled together
the results of all the gut-hormone tests.
On the top in red is when they ate their burgers slow
and in blue is when they ate it fast.
And you can see there's a suggestion
that when they ate the burger slowly,
their GLP1 levels went up higher.
This is great. Because for this group,
we think part of the reason they might be overweight
is because they have lower levels of this fullness hormone, the GLP1.
So this could be a game-changer for them.
A little tweak like this might get them fuller. That's right.
They not only have less time afterwards to eat more food,
but their fullness hormone, their GLP1 levels, go up a bit higher,
they will be fuller at the end
and feel fuller for a bit longer.
That's brilliant. OK, a double win.
So it turns out that when your parents told you to eat more slowly,
they had a point.
This is the sort of science that will help the Feasters
lose those final pounds before the end of the experiment.
After I had finished the burger that took 30 minutes to eat,
I did feel as if I'd had a meal.
I felt as if, um...I'd taken my time.
It didn't feel almost...
Yesterday, I felt like it was a snack almost
that you just ate on the hoof, you got it down and that was it.
Slowing down how fast you eat is a good tip
not just for the Feasters, but for everyone.
If you want to find more tips for losing weight
and what type of eater you are, go to -
For our next diet group, keeping their weight on track until the end
is going to be difficult
because food is always on their minds.
Hello! Hi!
You all right?
How are you? Are you well?
The Constant Cravers were identified using genetic tests.
They scored highly for genes
that give them a stronger drive to eat.
They're constantly hungry.
Earlier in the experiment, our scientists asked the different groups
to wear eye-tracking glasses at a funfair.
The Constant Cravers looked at double
the number of food items compared to the rest.
This group have been put on an intermittent fasting diet.
This means they eat normally for five days,
then go on a calorie-restricted diet for two days.
For two days each week, you're going to have no more than 800 calories.
The benefit of this diet is they only need to battle
with their hunger for a couple of days a week.
For Constant Craver Mo Crookes from Sheffield,
a hungry feeling is still ever present.
I'm constantly wanting to eat. I crave food.
Mo's start weight was 23-and-a-half stone.
He's been doing well, having lost just over a stone.
But sticking to the plan when the scales aren't moving
is really upsetting him.
The first few weeks, weight seemed to abandon ship,
but then it's half a pound, a pound.
Take my bloody socks off and I've lost half a pound.
Now, I've learned a lot of lessons
and my mind's in a totally different place.
BUT I'm still finding it hard to cope with the frustration.
It gets you down, it gets you black, it gets you pissed off
and you think of your hard work and you think,
"I'm just wasting my time."
"I've always been a loser, I've always been fat.
"Why is it going to change now?"
Many of the Constant Cravers are finding the dieting
especially tough at the moment.
Geneticist Dr Giles Yeo has brought them to a meat cold store
for an unusual demonstration of one reason why.
He believes that the Constant Cravers' genes
may be making them even hungrier now they're shedding the pounds.
OK? Come in, come in.
Come on in, guys. Welcome!
OK, Giles, why have you brought us to a meat freezer?
TANYA LAUGHS
It's all about this stuff over here.
This white squidgy stuff is fat, OK,
and it sits underneath your skin.
Now, our body has a very good gauge
about how much fat you guys actually have.
The body uses a hormone called leptin to measure our fat levels.
Leptin is produced by fat cells
and signals to the brain how much fat we have.
The higher our fat levels, the more leptin we produce.
And the stronger the signal to our brain
that are fat stores are well stocked.
Imagine this to be a representation of yourself.
Your body, here's your fat.
This dial here represents your leptin levels, OK.
So as you lose fat...
..your leptin levels begin to go down.
Your brain senses this and does everything it can
to bring you up towards your pre-diet weight.
So as you lose weight, your brain does not like that at all
and has to defend against it.
So when we lose fat, our leptin levels go down
and signal to the brain that our fat stores need to be replenished.
This happens to all of us,
but if you have obesity genes, these play a trick on your brain.
These genes we've measured in you guys,
what they do is interfere with leptin-signalling to the brain.
So your brain thinks you have less leptin and therefore, less fat
than you actually do, OK.
And the effect of this is to make you feel hungry.
So when you then started your diets and you started then losing weight
and your leptin levels started going back,
you're then fighting a losing battle.
You're getting hungrier and hungrier as your leptin levels dip
even below what they were when you started.
The Constant Cravers do appear to have a raw deal.
As they lose weight, their hunger levels rise higher
than those without the genes.
And they were hungrier to start with.
Does this kind of resonate with your experience
in terms of how it's been throughout the diet?
Do you find you're hungrier now
than you were before you started the diet?
I still crave and still feel hungry.
I still have food on the brain constantly.
I've gone through two or three weeks where it's been really difficult.
Is it because you're feeling hungrier? Yes.
Because you've lost a lot of weight,
but actually, you're feeling hungrier. Yes.
Bye. See you later. Bye.
So dieting is going to be more difficult for the Constant Cravers.
But Giles thinks he might know a way to help.
He wants to see what effect breakfast has
on their food choices for the rest of the day.
Giles has split the Constant Cravers into two groups.
One group is allowed to eat breakfast,
but the other group is only allowed to sip water.
I'm grateful that I've been chosen to have the opportunity
to have something to eat for breakfast
and not have to skip breakfast.
Thank you.
I think I would've been very grumpy
if I didn't have the breakfast, to be honest.
I'm not thinking about it, that's what I'm trying to do.
I'm concentrating, keep sipping the water. Think positively.
Because they're all friends. Might not be for much longer(!)
Yeah.
I can see the nice sausages and things over there, so...
Oh, God! THEY LAUGH
With lunchtime drawing near,
Giles is ready for the next stage of the experiment.
So, hello, guys. So half of you have had breakfast...
Yay! ..and half of you have not had breakfast.
THEY GROAN
What you have in front of you, each of you has a tablet
and a score sheet.
And on the tablet, there are 108 pictures of foods.
And what I want you to do
is to score the foods that you like and don't like.
If you like the food, give them a five,
if you don't like them, give them a one
and everywhere in between.
OK, so let's go.
Our Constant Cravers have a choice of healthy foods
verses fatty and sugary foods on their tablets.
Giles wants to find out which ones they find most appealing.
We're interested in trying to see which foods they find desirable
and which foods they don't find desirable.
Remembering that half have had breakfast
and half have not had breakfast.
I'm particularly interested in the differences between the two groups.
Our two groups have rated their preferences
for the healthy and unhealthy foods.
After some number crunching, Giles has the results.
So the results of the experiment are in and they are very interesting.
Amazingly, those of you who had breakfast actually preferred
the lower calorie foods to the high calorie foods.
Hmm!
In fact, the group who did not have breakfast
preferred the sugary and fatty foods 40% more
than the group who ate breakfast.
So what does this mean for our constant cravers?
I think for those of you with hungry brains,
if you have breakfast, I think then it will help you desire
less calorie dense food throughout the day.
So this is a good tip for losing weight,
and also for maintaining weight loss.
Yes, because three quarters of successful dieters have breakfast.
Is that something you knew about? How do you feel about that?
Anything that makes life easier and helps maintain the weight loss,
and, once I get to where I want to be, keep it off,
it has got to be worth doing that, and introducing a lifestyle change.
OK, Sharon, you have said you found the die harder and harder
because you felt hungrier and hungrier.
Does this information kind of change the way you think
about how you are going to run the diet?
It does make sense,
because I have been trying to get into having breakfast, but,
you know, time, and tired,
and things happening, I do sometimes skip.
So it is a definite positive piece of information
that I need to keep here, and it will help me move forward.
We are 10 weeks into our diet experiment.
Weight-loss has been slowing down for many of the dieters.
But our experts have been giving them advice
to help them through this rough patch.
We have discovered that as you lose weight
you should eat less, to counter changes in your metabolic rate.
We found that the slower you eat, the fuller you will feel.
And that eating breakfast may help you
make healthier choices later in the day.
Now, our experts want to help our last group
to know what to do if they break their diets.
At the start of our experiment we identified the Emotional Eaters
using psychological questionnaires.
These are people who turn to food when anxious, depressed, or stressed.
We put them through a fake driving test...
THUDDING
How I feel at the minute, I just want to cry!
..and saw that stress made them eat much more
than people from the other groups.
Our scientists put them on a group support plan.
This uses the encouragement of others to help stop them
turning to food when they are down.
To get that support they are all attending dieting clubs.
And they are also receiving cognitive behavioural therapy.
This gives them techniques to manage the thoughts, feelings,
and behaviour associated with comfort eating.
Derek is an Emotional Eater from Edinburgh.
He started the experiment at 22 stone
and has lost just over a stone so far.
But he still sometimes turned to food, like chocolate,
to help him get through the day.
If I'm feeling really upset, or if I am feeling stressed,
it is such a powerful emotion to want to eat those things.
I have found that when I have been tempted
and given in to that temptation it is almost too easy to then
fall off the wagon, so to speak, and then want to have more.
Behavioural scientist, Prof Paul Aveyard,
wants to see how our Emotional Eaters respond when they break their diets.
He has invited them to meet master cake baker, Jill Blackhall.
They are being split into two groups, purple and orange.
Each group will be told two very different stories
about these two very indulgent cakes.
So, these two cakes are decorated differently
but actually underneath they are identical.
A slice of each of these cakes is a whopping 700 calories.
Now, each of our Emotional Eaters will be given a slice of cake
but our first group getting a slice of this cake will be told the truth.
We will tell them this is highly calorific so that they know
that once they have eaten the cake they have broken their diet.
However, our second group of Emotional Eaters getting a slice of this cake
will be told exactly the opposite,
they will be told that it is low in fat and sugar,
so once they have eaten it
they will believe that they have kept their eye on track.
With the purple group we want to see if knowing
that they have had a lapse in their diet
will trigger a common psychological response.
One that lies behind why so many diets fail.
Oh, wow!
Absolutely gorgeous. Do you want to...? It smells gorgeous.
It does smell gorgeous, doesn't it?
Do you want to describe what we have got here?
Yes, underneath the rose swells here this is a red velvet cake.
ALL GASP
So, very indulgent.
We are telling them they are here to learn about calories.
The purple group is being told the truth about the calorie content
of each slice, so when they eat it they will know
they have broken their diets.
I don't want to ruin the enjoyment,
but it is interesting to note the calories this slice would be.
Can you guess? What do you think? About 500. OK. What do you reckon?
About 450. OK. And the grand total is...? 700.
Wow!
And observe that we really are upset about it(!)
ALL GASP
And now for the deception.
We are going to pretend to the orange group that this cake
is low in calories, so they will believe they haven't
broken the diet by eating it.
We need to talk about calories. Can you guess?
Is it 500 calories a slice? OK.
I am guessing, about 200, 250 calories a slice?
190 calories per slice. Wow! That size of slice? Yeah, yeah.
That is amazing!
That's the white lie, of course. Now for a spot of cake decorating.
At the deep end each group will have a tea party
where they can eat their decorated cakes.
What Paul is interested in is how much of these cakes
each groups eats when they are left alone with them.
Now, you might think it is a bit cruel of us
to encourage one of our groups to fall off the wagon
but it is for a very good reason.
Temptation is everywhere whether you are eating with your friends,
at a wedding, or maybe there is a birthday party at the office.
And, really, for our participants to manage their diets successfully
one of the things we have to help them learn
is how to deal properly with those, sometimes normal, small indulgences.
The tea parties have been recorded in secret.
Paul wants to see
if the two groups eat different amounts of their decorated cakes.
First up, the purple group, who know they have broken their diets.
So, the experiment has started.
I suppose we are looking here to see
whether they have got the coping strategies not to regress.
Yes.
That's definitely got that home-made taste, hasn't it?
We could do a cake diet. Take for dinner, for breakfast...
That cake is really, really nice, I enjoyed that.
They are obviously really, really enjoying the cake,
don't seem to be worried about eating it,
even though they are on these diets.
They are saying, "Let's do a cake diet",
so they are loving the cake. Yeah, yeah.
What we are looking at, really, is to see whether this...
When they know they have broken their diet,
will that trigger a relapse?
See, what a lot of people do when they have a lapse and they eat
something they know they shouldn't, it triggers catastrophic thinking.
Catastrophic thinking?
Yes, so people will say to themselves,
"Look, I just can't stick to a diet."
So they give up on the diet and they overeat in a major way,
and have a major relapse.
And now for the orange group, who think they have stuck to their diet.
Right, how many calories is in this one?
Shouldn't really eat this, but I'll need a little bit.
Oh, so Brent just said we shouldn't really be eating this.
Now, this is the group think the slice of cake
they had earlier was low-calorie.
So presumably they are not thinking they have already broken the diet.
So what are you seeing here?
This group are practising restraint, and that is because
they believe they have not fallen off the wagon,
they have not broken the diet,
so that has not triggered those catastrophic thoughts
which undermined the motivation
to carry on with their weight loss programme.
Behind the scenes, Jill has weighed the cakes
before and after the tea parties
to measure just how much each group has eaten.
It is time to find out the results.
What this experiment was doing was looking at how much cake you
would eat in the second sitting,
based on what you thought you had eaten in the first piece of cake.
So, we told you it was 700 calories in a slice, and we told you
that it was a low-fat, low sugar cake, and 190 calories per slice.
It was 700 calories per slice. OK? Oh, no!
What you thought was you had only had a few calories in that cake.
So you were still on your diet plan, still on track for the day,
so when it came to the second sitting of cake,
you only ate a small amount.
What do you guys thought... LAUGHTER
What you thought was that when you had eaten the first slice of cake,
that the diet was already blown, right?
Yeah, pretty much!
And so when it came to the second sitting of cake, you thought,
well, that's it, yeah, what the heck? Let's just blow this diet!
Talk about going for a curry! LAUGHTER
And, boy, did you blow it!
You ate eight times as much cake as these guys, in the second sitting.
It's a staggering difference.
The purple group, who thought they had broken their diet,
eight nearly two kilos of cake between the four of them.
So, this experiment was about what we call catastrophic thinking.
And what we've been working on together over the time
is the way in which you can turn those thoughts around
and not let a lapse,
a non-planned cake eating incident, lead to a relapse.
Even if you do have a really bad day,
get back on track as soon as possible.
That's the curry out the window! That's the curry out the window!
Even a few weeks ago I fell off the wagon
and I did exactly what the other group had done, I kind of thought,
oh, well, as well to be hung for a sheep as a lamb, sort of thing.
So, yeah, it definitely all made sense this afternoon.
OK, fair enough, I have had the cake,
but I don't have to continue by going for the curry.
I am not going to beat myself up about it, I am back on track.
And that's something that's... It's another vital moment.
There is now only one week of our diet experiment left.
At the nerve centre our experts want to see
if their tips are helping the dieters
through this difficult stage.
So, I was previously...here.
And where I am you can see. Now here.
When I went to screening I was 24, 25 stone.
I mean, way out of control.
Doing things like this brought it home to me,
because that's a 25 kilo sack of chickenfeed.
And that is just about what I have lost in weight.
And heaving that around, as you can see, is quite hard work.
12 weeks ago I was carrying this with me,
24/7, every day of the week.
I know other people on the dieting experience
have been losing weight faster than I am,
but I am really, really happy with my weight loss.
Really happy with that two lbs a week.
If I can do that and create this new eating lifestyle
and new approaches, I think I am fantastic.
I am now more than two stone lighter,
so absolutely chuffed with that.
It is a lot more than I anticipated.
The challenge now is trying to keep it off.
I need to make a life change and this is what is going to be hard.
Anybody can do anything for about 12 weeks,
about what we would be on this programme for.
And I don't want to do it for just 12 weeks.
There is so much positivity there.
How are they going to keep this up?
Because they want this to last forever.
This is really the key issue and Heidi is absolutely right,
they need a plan to maintain their weight loss.
People really need to remember that keeping the weight off
takes real effort and energy.
And if they don't concentrate on this they will very easily
slip back into their old habits and put the weight back on again.
So as we near the end of the experiment
the volunteers are starting to think about how
they will maintain their weight loss for the rest of their lives.
Putting the pounds back on again is a common problem for many dieters.
There is one thing that could help all three groups
keep the weight off for good.
Exercise.
Exercise isn't the most effective way to lose weight, initially.
But once you have successfully lost weight
exercise is one of the best ways to make sure it stays off.
For one of the Constant Cravers, make-up artist, Morgan,
doing exercise is good in theory, but, like most of us,
he finds it harder in practice.
There we go.
9:20PM. I have just come back from work. I don't want to exercise.
I am tired, I don't want to bother, I just want to go with
a glass of a diet drink, watching a bit of TV, and just relax.
I was ready.
I'm a kid, I booked myself to go for a spin class,
but now I'm too exhausted.
Fitness scientist, Jason Gill, from the University of Glasgow,
believes he might have a way to fit exercise into our daily routine.
And he is going to test his theory by putting Morgan
through his paces for the day.
So what we are going to do, a lot of things today,
the first thing I want you to do is just do an exercise
session on the, sort of, exercise bike.
Today Jason want to measure how many calories Morgan burns
during different types of activity over the course of the day.
First he wants to see the effect of an intensive workout.
Start pedalling and I will set the work rate.
Just like the hoods we saw earlier this kit measures how much oxygen
Morgan breathes in, and how much carbon dioxide he breathes out.
Only this time, it is when he is active.
It calculates how many calories he has used up.
So, keep pedalling at the same speed.
I am just going to make the resistance a bit higher.
Look, you're cycling for France!
That's great. Keep those legs going, Morgan, that's really, really good.
Last 10. Just keep driving those legs, Morgan. That's really good.
And easy. Ease it back, ease it back.
Well done, that's you done, Morgan.
James Bond!
Morgan doesn't know it yet
but he has burned 240 calories in 30 minutes.
Get out, get a shower, and then I'll get you,
we'll see you for the next bit.
Jason now wants to see whether he can get Morgan
to burn the same number of calories
doing everyday activities.
So, we are taking the calorie counter out and about.
First up, a spot of food shopping.
Right, all I need you to do is to grab a basket,
walk round the shop, and grab at least 20 items
to fill the basket up.
OK, let's do it. OK, off you go.
Jason is recording how many calories Morgan uses
going around the supermarket.
He has asked him to use a basket instead of a trolley to make it
a bit more energetic.
Beans, a four pack of beans!
Just keep on going, you haven't filled the basket yet.
Another couple of aisles and we'll be done.
So what we are seeing here is really interesting.
Tracking the calories while he's going around the supermarket,
and it is rising gradually as the basket is getting heavier
and he is filling it up with more items.
He is burning many more calories now than when he started to shop.
Well done.
Nearly at the till now. Thank you.
Morgan's banked 40 calories from his shopping trip.
Now it is on to activity number two.
All Morgan has to do is talk on the phone, standing up.
30 minutes on the phone like this clocks up 60 calories.
Morgan's next task is to walk instead of taking the tube.
Keep walking, Morgan.
We are not walking very fast, we are strolling along,
and he's at about six, six-and-a-half calories per minute.
Just walking along.
Finally Jason wants Morgan to climb a few stairs.
So it is time to tally it all up.
Has the general activity of the day
come close to the calorie count of the exercise bike?
So we walked a couple of tube stops, about 20 minutes.
How many extra calories? I would say...70 calories. It has about 110.
That's good. That's pretty good.
And then five minutes of walking up and down the stairs, a day,
would get you another 60. OK.
So, we add that all, that's 100...
270 calories per day. It's actually more than going to the gym.
This is something I can actually fit into my lifestyle,
but this is something I can fit as well,
so if you combine them all together, they could work even more.
So walking, talking on the phone, and shopping,
actually burned more calories
than his half hour intensive workout.
If Morgan did activity like that every day of the week
he would lose the same calories as a four-hour run.
Well, we are coming to the end of our diet experiment,
and it has been a fascinating 12 weeks.
You know, what we have done is really groundbreaking.
We have shown that there are different reasons for overeating,
both biological and psychological.
We have learned how the body responds differently
to dietary measures.
And finally, our volunteers have discovered things
about themselves and their bodies that they never knew.
It's the last day of our diet experiment and we have invited
all of our volunteers back to Liverpool for a final weigh-in.
I am not feeling sad that it is the last day
because I realise now that I have got all the tools I need
to take this forward.
I am feeling nervous and excited. All in the same go.
It is like momentum, it has, like, built up to this point.
Over 12 weeks our 75 volunteers have been following diet plans
specific to their genes, their hormones, and their psychology.
We are about and find out how well the personalised diets have worked.
Hello, everyone.
After three months we have reached the end
of our weight loss experiment.
We are about to find out
if this new personalised approach to dieting has been a success.
So it is time for the final weigh-in. Come on.
CHEERING AND APPLAUSE
A stone and a half, total weight-loss.
How do you feel about that? Yeah! I have lost it, haven't I?
Moving in the right direction. Are you going to keep on, keep going?
Oh, definitely, yes, I've only got about another six stone to go,
so it should be a couple months!
Just over a stone. I'm so happy, because it is going down.
You are on the Feasters diet, so it is high-protein, low GI.
Do you enjoy the diet? You know what? It is a doable diet.
I think it's always come to be a struggle, but, it is working.
That is two stone, over two stone. How have you done it?
Just by sticking to the plan. That's impressive, a stone and a half.
I'm over the moon with that. Are you? Yeah.
A stone and a half in three months. Really pleased, yes.
What would you say is the high point of this whole experience?
Changing my whole lifestyle, I think, has been the high point.
Getting a good understanding of why I was overeating.
Getting to grips with that.
Nearly two stone. Are you happy?
Really pleased with that, yeah, that's fantastic, fantastic.
Congratulations. Thank you very much. That's a very happy lady there.
Yes, I am. I am delighted.
These are tremendous individual results.
But how has the group than overall?
At the start of the experiment we set them the goal
of losing 5% of their body weight, through personalised dieting.
Other studies show that this is a tough target to reach.
Will their combined efforts be enough?
Nutrition scientist, Prof Susan Jebb and behavioural scientist,
Prof Paul Aveyard, are compiling the results.
Before we reveal the group total we just have to tell you
who has lost the most weight over the last 12 weeks of our diet together.
And that would be...Bob Marchant.
CHEERING
Bob, you have lost, in total, three stone and four lbs
since we started this diet.
Congratulations. Congratulations. Whoo!
But it was never meant to be a competition.
I want to do a straw poll.
And the question we want to answer is, do you feel that taking diets
based on your biology and your psychology has been more effective?
So who here feels they will stick with this diet that we have
picked for you, moving forward, and that it has been successful,
and it will continue to be successful?
If you feel that, please, hold up your group card.
Wow! That is almost everyone. Almost everyone.
Two colours left on the ground. So now here is the big result.
How have you done as a group?
You have bonded amazingly, you have supported each other,
and this is your extraordinary result.
Over the last 12 weeks you have lost, in total, 654 kilograms,
that is 103 stone.
CHEERING AND APPLAUSE
Our diet experiment has been a success.
The volunteers group target was 5% and they have smashed it.
They have lost more than 8% of their body weight.
And they have achieved it through new scientific methods tailored to their
biology and psychology which have never been tested like this before.
I think it was a really massive success
and I think everybody has just done amazingly.
Over 100 stone, that is unbelievable, fantastic.
I'm just really happy that my eating habits have changed.
The weight has fallen off, which is everything we've been told.
Everybody has lost weight. Everybody is going forward.
Almost universally everybody is positive.
So, yeah, it has been a great success.
So have you got any final advice for people?
I think what I'd really encourage people to do is not to be taken in
by the latest fad diet, the latest celebrity endorsement, rather than
looking at the diet, what I would say to them is, look at yourself,
think about your own eating behaviour
and really try to understand what is going to be
the best diet for you.
It is going to give hope to hundreds of thousands of people.
Millions of people out there, who have dieted and failed in the past.
So it is still early days for the science of diet personalisation
but as our experiment shows there is huge potential for this approach
to dieting, one that suits not only our biology but also our psychology.
So if you want to lose weight, rather than trying the latest fad diet,
why don't you think about one that fits you and your eating habits?
To follow up on any of the advice given in the series,
or to find out what diet might suit you best, go to our website...