The Truth about Fat Horizon

As a nation, we are slowly

but surely getting fatter.

We're all eating well.

Maybe too well.

I'm Gabriel Weston and I'm a surgeon and writer.

I think this obesity problem has become bad enough

to be called an epidemic

But it's a puzzling one.

Here's the mystery.

We all live in the same environment,

surrounded by delicious food 24/7.

But we're not all the same shape.

Some of us balloon, some of us get a bit chubby,

and some of us just stay thin

What is it about this epidemic that operates so randomly?

For the unlucky majority,

nothing seems to stop the pounds piling on.

We ask patients to go away, eat a little bit less food,

do more exercise, but it hasn't worked for the last 2,000 years

and we need to really come up with some better ideas right now.

It's tempting to see this epidemic

as a failure of willpower.

It's just something you want, you need, you know? It's fat.

But the latest research that I've seen

has forced me to change my mind.

I'm pretty shocked to discover that my assumption of a lifetime,

which is that I'm the size I am because of my character, is nonsense

And this new science may hold important clues

for fighting the fat epidemic.

I've been working as a surgeon for over ten years.

I love being in theatre. I've always enjoyed it.

There hasn't been a week gone by when I haven't loved being here,

and I can't completely explain why I do, to be honest.

It's a chemical thing. It's a great place to be.

I feel myself when I am here.

I specialize in skin operations.

Today, I'm removing small but potentially dangerous growths.

Sore bit coming up now.

Well done.

If you feel anything sharp,

let me know and I'll give you some more local.

We have a number of cases,

all of which are likely to be skin cancer.

They are either of the type that will just grow unless removed

or even the type that can spread and kill people.

The feeling that my surgical skills

are helping to treat cancer is really satisfying.

When I stick this knife into someone and they've got a skin cancer,

I feel happy about what I am doing and I enjoy it.

But there is one group of patients

we seem unable to help as much as we'd like.

These are the growing number of obese people

who are now coming in for surgery.

What we've been doing on this operating theatre

this afternoon has been quick.

We've seen lots of surgical patients really fast.

But in hospitals all over the country,

obese patients are bringing surgical operations

to a compete standstill.

They complicate the surgical process at every level.

They have tons of other illnesses

which make their surgical diseases complex.

They're extremely difficult to anaesthetise

and difficult to operate on as well.

This makes surgery riskier for thousands of patients every year

But it's not just a problem in surgery.

I'm also a mother, so I'm concerned

how this explosion of obesity

will affect our children and their children too.

What I want to do is look at some of the interesting new research

that's trying to explain what obesity is all about

and some of the ways we might go about

fighting this fat epidemic.

On the face of it, there seems an obvious reason

why the last 20 years has seen our weight soar.

We're eating more food than we need,

because it's more easily available than ever before.

I'll just try a little bit of this.

That is delicious.

Here in the modern developed world, food is everywhere

and it's rich in calories.

Spicy sausage.

-Mm, lovely.

-It's packed with flavour.

Some estimates suggest that most of us are now eating

over 200 more calories than we need every day.

And the truth is it's the fatty,

calorie-rich foods we love the most

Wow! A Portuguese custard tart.

This is literally my favourite food on earth. Here I go.

It's too good for words.

What I see at this market

is the collision of two different worlds.

Our bodies evolved in a prehistoric world where calories were scarce,

hence our love for the taste of the fatty stuff.

But our developed world is awash with food.

When our primitive biology feeds so richly,

the result for many is obesity.

In fact, nearly a quarter of the adult population

are now clinically obese.

So is there anything we can do about it?

To answer this question,

I want to start by explaining

how the obesity epidemic is actually doing us damage.

I want to talk about fat.

And as a surgeon, I can take a look at fat from a unique perspective.

From the inside out.

I've come to the Royal Veterinary College

to show you something rather surprising.

This isn't exactly the kind of anatomy I'm used to,

but it's as close to human as I'm going to get.

Food is a biological necessity.

And at the most basic level, fat is too.

It's just the body's way

of storing food between meals.

So fat is not all bad.

Now I'm cutting through the epidermis,

the dermis, down onto the hypodermis,

which is the subcutaneous fat.

It's quite hard work in a pig compared to a human being.

This layer of white, dense tissue here

is the subcutaneous fat

and this is one of the places where this pig, as well as you and I,

store our fat.

Subcutaneous fat can do this because it's made up

of billions of special cells

that are capable of expanding and contracting.

So this fat is actually protecting us

during periods of starvation

You might think that when a person becomes overweight,

it's this stuff making them ill.

But actually subcutaneous fat is not where the problem lies.

Now if I go deeper into the pig's body,

I find a different, more dangerous kind of fat.

I have to say that having not done any dissection of anything dead

in over ten years, it's a real pleasure

just to be able to dissect a carcass like this.

What I'm looking for now is something we call

visceral fat, which we've all got some of.

OK, I'm in.

Oh, my goodness. That is just too cool

This visceral fat, gathered around the most sensitive organs,

accumulates when we eat more than our bodies can handle.

There's lots of visceral fat here.

There's a bit of fat just coming off the bottom of the liver there.

That's intra-abdominal fat.

Too much of this visceral fat can lead to a surge in cytokines,

chemicals which have been linked

to diabetes and heart disease.

We can't live without fat,

with all the important roles it performs. But if we overload it

so that it can't work properly anymore,

we can't easily live with it either.

So, simply put, too much visceral fat can make us sick.

Everyone knows that how much fat you put on

starts with a few basic decisions.

What to eat.

When to eat.

How much to eat.

When to stop.

But what is it in our bodies that is shaping these decisions?

And how can we control it?

I've come to meet Dr Carel Le Roux, one of the world's leading

obesity scientists, who may have come up with some of the answers.

He's a former athlete turned medic,

whose own life story helped focus his work

So, what got you interested in obesity to start with?

Obesity is such an important disease at the moment.

There are so many people suffering from it,

and yet we as doctors are not able to help them.

We ask patients to go away, eat a little bit less food,

do more exercise, but it hasn't worked for the last 2,000 years

and we need to really come up with some better ideas right now.

His work started with an interest in what was controlling his own weight.

As a champion shot-putter,

he was continually trying to bulk up.

But however much he ate,

he couldn't seem to gain as much weight as he needed.

I was very motivated. I had a lot of willpower.

I wanted to get my weight up but, despite my best efforts,

my body would just not allow me to get out of this set point

where it wanted me to be.

His group started to investigate

what process in our bodies

might be controlling this set point in our weight.

And they started to look at some of our body's chemical messengers

A group of proteins which course through our body

every day, influencing our behaviour.

They're our hormones.

Hormones tell the body when to fight or to flee.

How to repair itself.

They even tell our cells when to die.

Then ten years ago, Le Roux was part of a research team

that made a startling breakthrough.

They discovered two new hormones, ghrelin and PYY,

that together seemed to control appetite and weight.

There was a hormone that actually made us hungry.

In 2002, we discovered there was a hormone that made us full.

how did the discovery of these two new hormones

influence the science of obesity?

It completely opened up a new chapter because for the first time,

we understood that the gut can actually talk to the brain

and influence how hungry you are or how full you are.

So now we understood why it is so difficult

for patients who are overweight to actually change their weight,

because these hormones work against them.

I have to admit, I feel a bit sceptical about this idea

that an overweight person is overweight

because of their hormones, but I'm not overweight because of mine.

Well, why don't we invite you to come to the hospital?

We'll do an experiment where we put your willpower

against your hormones and see which comes out best.

Today I'm hoping to find out how my hormones

might secretly be controlling my appetite.

If Dr Le Roux can prove to me that I am at their mercy,

I'll have to think again

about what's causing people to over eat.

-Can I take your coat?

-Yes, thank you very much.

-Grab a seat.

Have you eaten anything?

I think the last time I ate anything was 9pm yesterday evening.

All right. You're going to have some breakfast. Eat as much as you want.

You'll have a spread, so you can choose. I'm then going to take

some blood tests from you. What we're going to determine

from the blood tests is how does the gut talk to the brain.

It all starts simply enough

Somewhere in my blood are my appetite hormones,

helping me to decide what to eat.

Oh my goodness, look at that. It's a feast!

We also have something in the microwave for you.

Ooh, that looks really delicious.

I think you've hit the jackpot there.

I am now primed for the experiment.

Or at least I thought I was.

Well, we've tricked you a little bit,

because what we're going to ask you to do now is not to eat again

-until breakfast tomorrow.

-Wow, OK!

It's not what I was expecting. If I'd known before,

and this is why you're telling me now, I would have eaten double.

Your body will be able to cope with the fast,

but it will actually psychologically

bring all types of things to the fore.

Because, of course, if people become hungry, they become ratty.

So the next 24 hours were to be the battleground

where my hormones and my willpower would fight.

After just a few hours

I notice my hunger returning, and it begins to affect me.

I'm feeling very distracted by how hungry I am.

I'm having to concentrate a bit harder

on driving than I usually would.

Because I'm not feeling that I can drive

quite as well as usual.

Later, I can feel the changing hormones

really starting to alter my mood.

I'm feeling grumpy now Really hungry actually.

So I feel as if I want to make this as quick a visit as I can.

And my judgement too.

I'm going to stop and get some yoghurts.

Ooh. I'm also feeling like

I'm looking at them and feeling indecisive, which is not me at all.

And as I began to get really hungry,

food was all I could think about.

Over here, they have the...

The smell is just powerful and delicious.

They made the roast chickens there.

7am. Nearly 24 hours since I last ate.

And just one hormone measurement left

before I can give in to my hunger.

Morning! How are you?

-I am ravenous.

-Really?

-And a bit tired.

Well, let me take your coat and let's get right into the experiment.

Dr Le Roux does the last blood test and I can finally eat.

And I immediately tuck into

the sweetest, fattiest food on the table.

And I'm going to have my first bite of food in 24 hours.

It was quite possibly the best meal of my life.

It's really, really good.

But what I'm really keen to find out

is how my hormone results compare to those of an obese persons.

Take a seat here. The results are in

and the good news is that you're completely normal.

-Great!

-What we see

that immediately when you've had your meal,

your hunger hormone starts falling

and then after a short period, it starts

rising. And by the beginning of the next morning,

it is incredibly high.

Which is exactly how I felt. I was beside myself by then.

And how about the fullness hormone?

Looking at that, you see the opposite.

Immediately when you eat, the fullness hormone shoots up.

It makes you feel full,

allows you to stop eating.

And then it starts plummeting and it stays down for the whole duration.

So how would that compare with the profile of someone who had...

who was overweight or obese?

With the hunger hormone, surprisingly,

obese patients didn't have as much hunger as we expected.

The hunger hormone never gets switched on

and it stays at the same level throughout the day

and then starts rising if we actually had to deprive them of food.

So it's a little bit like a light shining dimly

but where your light shines brightly,

it gets switched off. When they eat the light stays on.

So that constant nagging sensation remains throughout the day.

Which is really interesting because not knowing about this hormone,

what I expected was that you would tell me

that someone who was overweight had a much, much stronger hunger hormone than I do

but in fact what you're saying is that that's not the case.

You're right and we were surprised until we looked at the fullness hormones

and suddenly it started making sense

because what you would see in somebody that is overweight,

their fullness hormone only rises a small amount

and then comes down again.

So they actually never get the feeling of fullness.

And you would hear that very often speaking to people who are overweight.

They'll say, "I'm not that hungry but, when I start eating, I can't stop."

I'm pretty shocked to discover that my assumption of a lifetime,

which is that I am the size I am because of my character,

is nonsense.

And it seems from what you're saying,

as if I just have a fortunate hormone set.

If your hormone levels were different,

the battle would have been much harder.

Had I been asked to starve a minute longer,

I'm not sure I would have managed.

My hunger hormone was so powerful

that it actually affected my decision about what

and how much to eat.

You actually ate 170 calories more than you would have done

in comparison to the previous day.

So not only did you eat the wrong food,

you also ate more food in total.

And that's what happens to patients who are overweight.

They don't feel full after they've had a meal

and they have to consume more food and the wrong food.

What it's brought home to me

is that obesity is not just about will power.

Its also about our biology, our hormones.

But that's not the end of the story.

This epidemic is clearly complex with many other causes.

And I'm particularly interested in what we can learn from genetics

because I can see that fat parents often have fat kids.

And I want to find out if there are clues here

to help us tackle the problem of obesity.

There's a really interesting group of people

who have found themselves unexpectedly at the forefront of this research

Our similarities - our voices, height, eyes, teeth,

-noses, dimples...

-Dimples, I've got one here.

And I've got a dimple on this side.

Nature's own genetic experiment...

Birth marks on the back of our necks.

And little freckles and moles on our body in certain places.

..identical twins.

-Feet, both flat.

-Oh, yes, very.

Meet Elaine and Liz.

For most of their lives, they have lived within a mile of each other

and shared almost everything.

-Oh, do you remember these pictures?

-Yeah.

Oh, so cute.

I think we were similar. Very alike.

Yeah. Very alike there. Definitely.

We just did not want to have our pictures taken.

And, like most identical twins,

as children they were like as peas in a pod.

And this one is a school picture.

-They couldn't tell the difference.

-Not at all.

Watching these two it's clear that the relationship between twins is extraordinary.

There is just a special bond, which you can't explain really.

-Its just being together...

-Together.

-Being together.

-All the time, yeah.

-As one.

-One, but...

-But separate.

-..but separate.

And now Elaine and Liz have found themselves

right at the heart of obesity research.

For the last 20 years,

one man has been studying thousands of identical twins.

For Professor Tim Spector, twins are a fascinating experiment

because they can reveal the difference between what we inherit through nature -

the genes we are born with - or nurture - the environment we experience.

What is it about twins that helps you

when you are looking at heritability?

Twins are the best model in humans of actually working out

what proportion of ourselves, our traits or diseases are due to genes

or due to our environment, because you compare identical twins

and non identical twins, and the two types of twins

both sharing the same environment,

so only similarity in one group compared to the other

must be due to their genes.

Spector's work with twins convinced him

that nature - our genes -

was the most important factor in causing a whole host of traits,

from freckles to height and, as it turns out, weight.

But that was until he met identical twins like Elaine and Liz.

Because, while they share many traits...

Everything was virtually identical.

..there's one thing that makes them rather different.

Say about a stone and a half.

-I would say at least two and a half stone.

-Yeah.

-Yeah.

-Definitely.

The sisters are what's known as discordant twins.

And their very existence flew in the face of all Spector's ideas.

It was a bit of a shock because I'd spent 15 years of my life

trying to convince the rest of the world that things are heritable

and I'm suddenly having to say,

"Hang on a minute, genes aren't the whole story here, clearly,

"because these identical clones are behaving very much more differently than we thought they should do."

The question was, what was making these twins so different in weight?

They had the same genes, they shared the same environment.

So, like 99% of identical twins

they should have been exactly the same weight.

What level have you got yours on?

No wonder! You've got yours on one, mine's on three!

And it turns out Liz and Elaine are not unique.

Over the last year Tim Spector has discovered another two dozen of these rare discordant twins.

Hello. I'm Gabriel, lovely to meet you all.

I'm just bringing some coffees in.

I'm intrigued to talk to these twins

to see how their identical genes

have made them into these genetic paradoxes.

Maybe you could just tell me a couple of things about

what is the same and what is different about you.

Some are still so similar its hard to tell them apart.

-I'm Debbie.

-I'm Mary.

We very much like the same things, don't we?

Out taste in clothes is similar.

Some look different and yet still have that remarkable twin-ness.

-I'm Angela.

-And I'm Irene

We both have the same kind of silly sense of humour,

where we can see something and nobody else understands it

and we just burst into uncontrollable giggles.

And some seem more like normal sisters than twins.

-I'm Fiona.

-And I'm Jane.

We get on a lot better now that we are a lot older,

but unfortunately we live in different parts of the world.

Today, these twins are in London

so that Professor Spector can start to work out

why they are the same but different.

You guys are special

because most identical twins are very close in weight.

You're not. Basically, That's the simple sort of...

You don't have to be so blunt.

THEY LAUGH

In the past we've always said that things like putting on weight

or your height or whatever are completely determined by your genes,

and yet you are walking examples of how exactly that's not completely true.

Spector is putting these discordant twins through a barrage of tests,

painstakingly looking for clues to how they end up so different.

He looks for subtle differences in DNA between Liz and Elaine.

We're going to take this bit of tissue from you

to see how it differs between you and your sister.

And he even checks for tiny DNA variations

in different parts of the same twin.

So we get your nail clippings. And that's to get extra DNA

to see if the DNA in your nails is different to that in your blood.

The answer to the puzzle of why twins with the same genes can be different weights

seems to be this.

Spector now believes it's not enough just to have a gene,

it has to be activated or switched on.

And the larger twin had her fat genes switched on

where her thinner sister hadn't.

Something has switched in them,

has just switched some of their genes from one position to another

and that has altered what's happened to their metabolism.

And, because they are so similar, our idea is that we can track down

what those chemicals are

and what those genes are that are changed between the two.

This new science of how the environment can switch your genes on and off

is becoming more and more important across modern medicine.

Its called epigenetics. But the question now is,

what was causing these genes to be switched on or off?

Spector has been looking for something that sets one twin's experience apart from the other.

I maybe got a bit more attention. I had to go to hospital with our mum

-so I suppose I had stresses early on, didn't I?

-Yeah, yeah.

When do you think the changes occurred or you noticed any differences between you?

I think the changes happened when she got married and moved away.

I was married but I had family closer to me

and she didn't have any family closer to her.

And I think that's possibly when the change occurred.

I think that's probably when it did.

I'm just aware, as we are talking to these ladies,

that there is so many things that might go on at any one time

between the lives of two different women.

How do we know that we are not just randomly selecting factors

that could be confounded by hundreds of other factors?

You are absolutely right

and taking one pair, a snapshot of your life in retrospect,

which is full of false memories is not a reliable way of doing science.

So none of what I'm saying will be based on one or two twins stories

but only by doing this systematically

across hundreds of twins to see what the common factors are.

And Spector thinks he's seeing some common factors in all his twins.

His theory is that stress can create parallel

but different destinies.

What was interesting was three out of the five pairs

did give us a story of how, when they were put under stress,

they reacted differently.

For me, what's so exciting about Spector's work,

is that if he can understand what turns the fat switch on,

he might find a way to turn it off again.

To stop obesity in its tracks.

I think it's very exciting looking into that future.

We already know many of the genes are responsible for obesity,

we're going to find hundreds and thousands more,

but the key to this is how we can change those genes.

What Professor Spector was saying quite strongly to the twins today

was, "Even if something has happened

"to predispose one of you to putting weight on,

"where the other one has been free of that, this is not set in stone

"and you could do things, although it might be difficult,

"which could reverse whatever signal has taken place

"which has led to one of you being fatter,

"and one of you being thinner."

It's strange to think that some small event in your life might change everything.

That tiny switches in your genes can fine tune how much and when you eat

and how you body uses that food.

But it's not the only way that our genes lead to obesity.

Today, I'm on my way to Southampton

to find out about an inspiring study based on this new science of epigenetics.

It's helping us understand what might be making our children fat.

Professor Keith Godfrey runs this ambitious survey.

-Professor Godfrey.

-Really nice to see you.

-Lovely to meet YOU.

-Lovely to meet you too.

His study is ambitious

because it starts before the child is even conceived.

I wonder if you can take me right back to the beginning where it all started.

Well, it all started over 15, 20 years ago

when we began looking at how a mother's diet before she conceives

might have lifelong effects on the development

and the health of her offspring.

Other surveys have begun during pregnancy

or have had modest information before conception

but this is the world's first of its kind.

These are some of the 12,000 women who joined up over 15 years ago.

The survey aimed to answer a single, huge question.

What were all the factors that might make their children obese?

So, once a week for those...

Was it influenced by the diet and lifestyle of the parents?

Five times a week. And once a week for sausages...

..and no beans.

Was it shaped by the nine months the baby spent in the womb?

Or was a child's weight a result of its experiences in the first years of its life?

OK, don't worry.

And then after 15 years of searching, they found the answer.

It sounds like an incredibly work-intensive job,

and what did it show?

We've shown that the baby's development in the womb

influences its risk of obesity six or nine years down the line in childhood.

It was a completely new cause of obesity.

It seems that the biggest single factor causing a child to be fat

was the nine months it spent in its mother's womb.

Amazingly, they explained something like a quarter of the differences

between the children in their degree of obesity nine years later.

This claim that a single cause adds 25% to the risk of childhood obesity

is enough to make any doctor sit up and listen.

And in your experience, is that a strong association?

We've never seen anything as strongly related to the child's obesity before.

In all the studies that we've performed over the last 20, 25 years,

never anything quite like this.

So what was happening in the womb that made this crucial difference?

Godfrey started to look at the genes

in the only tissue that links mother to child within the womb itself.

The umbilical cord.

So these are the umbilical cords that we've collected

and over 3,000 women in the Southampton Women's Survey

have kindly agreed that we could use their cord.

And how fresh is this specimen?

So this is a placenta and umbilical cord from earlier today.

When he analysed the cord he found something unexpected -

a single switch on a gene called RXRA.

And it was powerfully linked to childhood obesity.

And what controlled the setting of this switch was this...

The mother's diet.

If the mother is undernourished

or eats an unbalanced diet in pregnancy,

the baby thinks that it's going to similarly

be undernourished after birth.

Those babies tend to be thin at birth, but in our westernised

environments where there is not much physical activity

and high food availability,

those children are mismatched to that later environment

such that they progressively put on fat during childhood.

So the nine months in the womb turn out to be crucial

to your child's weight.

And with the right nutrition, it's something we can change.

I think that this work holds great promise for the future.

But right now the best health advice hinges on exercise and diet,

and of course that's right.

But you just have to look around you to see that its not enough.

So I'm interested in looking at other ways that scientists

are thinking about tackling our problem with fat.

I'm on my way to meet a woman who is about to undergo what

I think is a fairly extreme treatment for obesity.

But it's a treatment that might have much wider implications.

-Hi.

-Hi, I'm Gabriel.

-I'm Marilyn, come in.

-Thank you.

-Thanks for having me.

-That's all right. Come through.

Marilyn Walsh is a mum who lives in South London.

She weighs over 21 stone.

-Four years old I was there.

-Let's have a look, lovely.

Yes, but not, not thin, look at the chubby cheeks.

What have we got here?

I'd be about 9, and you can see the weight already.

-Yeah?

-Yeah.

Like most overweight adults,

Marilyn has found that diets have consistently failed.

And is this the stage that you were telling me about,

where your mum was already putting you on diets?

Yeah already, mum was already trying with the diets, already, you know,

carrot sticks, cucumber sticks at break time.

What these photos are sort of painting a picture of

in a way is the sort of lifetime of being overweight.

Yes, constantly having a weight problem, you know, which it is,

it's a... it is a weight problem.

Why can't you just lose weight, like why can't you just

not eat the things that are making you put the weight on?

It would be a bit like saying why can't an alcoholic

stop drinking. Why can't a smoker stop smoking, it's exactly

the same answer you'd ask them. There isn't, there isn't an answer,

it's... Something that's been with me all my life.

And you just feel hungry all the time?

I'm always hungry and always wanting food.

Worst picture of all. Biggest, I think, I ever was.

At the moment Marilyn is healthy,

but she know from her family the sort of problems that may await her.

My uncle, my dad's brother, he was I think about 35 stone,

suffered with weight throughout his whole life -

leg problems, stopped walking.

-Couldn't go anywhere, couldn't get in a chair so he had to sit on the floor.

-Wow.

He developed diabetes through it and lots of other problems.

And he did die because of his weight.

Unless something radical is done for her,

Marilyn is likely to face a future

of ill health and expensive treatments.

But Marilyn is now part of an experiment that might shed light

on how we might be able to change appetite and fatness forever.

I've come back to Imperial to meet up again with Dr Carel Le Roux.

Having convinced me that hormones shape our appetite,

he now believes that one particular kind of surgery

can fundamentally change the levels of these hormones.

Surgery on the stomach - what's called a gastric bypass.

Can you explain to me the mechanics of gastric bypass surgery?

So let me explain it like this.

That's the oesophagus or the gullet, this is the stomach

and this is the small bowel and this is the large bowel.

What the surgeons do is they cut the stomach

and they cut the small bowel.

So you are now left with you're oesophagus normal,

you have now a small stomach, so your stomach

goes from the size of your two fists into the size of your thumb.

The rest of the stomach remains in place

and the first 50cms of your small bowel and that's why

it's called the stomach bypass because we take the bottom

bit of the small bowel and connect it to the small stomach

and now food is bypassing the stomach

and the first part of the small bowel.

Reducing the size of the stomach obviously limits how much

a person can eat. But it has a more unexpected effect too.

It also changes the patient's behaviour.

So what you're saying is that in this particular operation actually

seems to affect someone's motivation to eat?

That's right,

the patients come to us in clinic and say,

"Doctor where did the surgeon do the operation,

"did they operate on my tummy or did they

"operate on my head because I don't feel hungry any more,

"when I do eat I feel full and all these changes

"have really happened in my head."

This is a really intriguing piece of research,

because it suggests a way that we might be able to alter

one of the most fundamental drives - appetite.

It's this operation that Marilyn has been selected for.

Her doctors at Kings College Hospital believe it's now the only

chance to save her from a future of debilitating illness.

-Hi Marilyn.

-Hello.

-How are you today?

-I'm Fine thank you.

Good. How are you feeling?

-Excited, ready and waiting.

-Good.

Any concerns at all or just looking forward to it

-and everything it means?

-Just looking forward to the new journey.

Good. Right,

good luck with it, I'm sure you won't need it.

The surgeon, Mr Ameet Patel has allowed me to watch the procedure.

It's a controversial operation,

sometimes seen as an expensive quick fix.

And until I made this film, it was view that I shared.

When I was here ten years ago working as a junior surgeon,

I have to confess I used to think it was a very extreme measure

for patients to take just because they were overweight.

In the old days we'd make a cut here and here,

we'd get inside, do the operation, it would be all open surgery.

Actually what we can do as an open operation we're doing as

a keyhole now. And the recovery's much better and quicker.

And I suppose the thing I see now which I didn't see then is that for

a lot of patients this is the end of a lot of things that they've tried.

Exactly, they want something to change their lives...

and that's what it does, it actually changes your life...

As its done by keyhole surgery

Mr Patel starts by making a series of small incisions on the abdomen.

And as you can see

we're going through the layers...

And that's fat that we are looking at the on the camera isn't it?

Yes. We're now going through the...muscle layers.

And here we've got to be a little bit careful as we

get into the abdominal cavity without injuring anything.

Let's put the CO2 on for me.

So some gas is being what we call insubflated through

the instrument here and what that does is gives

a kind of expanded sort of tented view of the anatomy he needs to see.

Its an operation that carries rare but serious risks.

There is the stomach.

It's quite a big stomach, you can see it all the way round.

This is all fat here?

This is all fat.

Resting on her stomach is a large slab of visceral fat, the fat

that in excess can poison our organs

causing diabetes and other diseases...

Before Mr Patel can connect

the small bowel to the bottom of the stomach,

what he needs to do is create the pouch which will be the new stomach.

Using a tool which both staples and cuts,

he creates the new smaller stomach.

So that's the new stomach there. And old stomach down here.

Old stomach on that side.

The operation usually results in the patient's losing

a third of their weight

and keeping it off for at least the next twenty years.

But if Dr Le Roux is right,

Marilyn won't lose weight just because of her smaller stomach.

It'll be because the operation has changed the way she thinks.

It's six weeks after the operation.

I really want to see what's happened to Marilyn.

Hi!

So Marilyn, what are you wearing?

These are my trousers from before the operation.

These are you pre-op trousers. Look at that! Wow!

That's amazing, that really is amazing.

But what I was really interested in

was how the operation had changed her appetite.

Now perhaps after a couple of table spoons

and I get a heavy feeling in my stomach which

I presume is what you would class as, I am full up now and I'll stop.

I can't eat any more. I never had that before.

I just want to stop and ask you a little bit

about the sorts of foods that you used

to choose by preference,

and the sorts that you would choose now?

I don't like the sweet or the fatty, the fatty isn't appealing anymore.

So the two tastes that drove you before, which were fatty

and sweet you now don't have any interest in?

No, but the sweet, when I tasted that hot chocolate last week

and the sweet it turned me, it was awful.

And the fat on the roof of your mouth, that was horrible,

trying to get rid of that takes a long time.

For Marilyn, I hope this is the beginning of much healthier

relationship with food, one that will finally be sustained.

It's clear that Marilyn's gastric bypass

hasn't just reduced her appetite,

It's completely altered her relationship with food.

And doctors are discovering this result again and again.

I really want to know how this works.

How is it possible that an operation

conducted on someone's stomach

can be so radically altering how their brain works?

I want to meet one of Dr le Roux's colleagues who is studying

how gastric bypass surgery actually changes patients' brains.

Dr Samantha Scholtz is a consultant psychiatrist at Imperial College.

So what got you into obesity?

Well as a psychiatrist I'm interested in human behaviour,

particularly the kind of behaviour which drives a lot of

what we see every day.

And if you think about it,

there are not a lot of stronger drivers

than food and seeking out food.

What's your specific line of enquiry in obesity?

I was interested in how obese people's brains

differed from people of normal weight's brains.

And what kind of tools were you able to use

for the science of your investigation?

When I first started psychiatry we didn't have a lot of tools

to see how the brain actually functions

and as time has gone on

things like functional MRI have become much more valuable.

Dr Scholtz is now using new MRI techniques

to compare obese patient's brains

before and after gastric bypass Surgery.

And today I am part of her experiment.

First she shows me a selection of high fat foods.

And the MRI scans my brain for activity,

indicating my subconscious desire for these foods.

Then I'm shown healthy foods. And the MRI measures again.

It's actually quite unnerving because with this machine,

you can't hide your feelings.

Later she shows me what she's found.

So you have some MRIs to show me.

This is the activity in your brain or the areas that are lit up,

the red areas, the areas that were more active when you were

looking at the pictures of high calorie appetizing food.

High fat food was clearly having very little effect on my brain.

This is a representative MRI for someone of normal weight?

Yes, fairly representative of that kind of picture.

On the other hand, if we look at someone

who is just about to have gastric bypass surgery

you can see quite a big difference here.

So this is the obese or overweight person's scan?

Yes this is activation in her brain looking at exactly the same

-pictures that you were.

-Wow.

-You can see a big difference.

-That's huge isn't it?

So you're seeing a lot of activation in areas which

we know are associated with rewards such as the orbital frontal cortex

but also area like the ventral striata and amygdala

which we associate with addiction and an emotional response to food.

The blue was revealing the obese brain's deep desire for fatty food.

So the green is the same lady

after she has had gastric bypass surgery about five months later.

The patient's brain response to fatty food has now totally changed.

So it's really a striking difference isn't it?

Yeah, I mean if we were to compare this person's brain after

surgery to your brain, so someone who is of normal weight,

we can see not a lot of difference there.

I'm really impressed.

The operation seems somehow to have pressed

the reset button in the brain.

I mean, this scan looks like you have changed the brain

of a fat person into the brain of a normal person.

In effect with bypass surgery is changing someone's brain

fundamentally so their reaction to seeing high-calorie food

is different and that would ultimately drive their choices

of food so that they stop having that battle with food that they

had before and are more like someone like yourself

who doesn't have that same battle with food.

Of course, surgery is not the answer for everyone.

But if Dr Le Roux can find another way to produce the effects

of the operation then he's found a powerful new weapon against obesity

The next point is maybe we can use devices -

we can put things into the bowel that can mimic the operation.

Or we can use injections or pills that actually will

do what the operations are achieving.

Now if we do that, that opens up the whole science of obesity.

And this will allow us in five years, ten years from now,

to have treatments that will have incredible benefits to the masses.

Obesity is clearly an incredibly complex issue

And one on which it is all too easy to take the moral high ground.

It's linked to our genes...

our hormones...

even to our brains.

So merely saying that it's a question of willpower

just isn't good enough.

And I've started to see that a new set of answers is emerging

which might help us to begin to defeat, what, to me,

is one of the defining epidemics of our age.

Subtitles by Red Bee Media Ltd.