0:00:02 > 0:00:05We're doctors, brothers, and twins, and we both love to eat,
0:00:05 > 0:00:09but which is worse for us - fat or sugar?
0:00:13 > 0:00:16It's the hottest question in nutrition right now,
0:00:16 > 0:00:20with sugar in particular being targeted as public enemy no 1.
0:00:21 > 0:00:25Sugar is the thing that's making you specifically sick.
0:00:27 > 0:00:30We're going to find out if too much sugar or too much fat
0:00:30 > 0:00:35can make you sick or pile on the pounds.
0:00:35 > 0:00:37You're a quarter fat!
0:00:39 > 0:00:43One of us is going on an extreme high fat diet.
0:00:43 > 0:00:46This is Tiger. Tiger is basically on my diet.
0:00:47 > 0:00:50The other, on an extreme high sugar one.
0:00:50 > 0:00:52None of these foods have any fat, do they?
0:00:52 > 0:00:54It's a high-carb, sugary diet.
0:00:56 > 0:01:00During these month-long diets, we'll be testing how our minds...
0:01:00 > 0:01:02I bought loads of them!
0:01:03 > 0:01:08..and our bodies cope with just eating fat or sugar.
0:01:08 > 0:01:09I feel like I'm out of juice.
0:01:09 > 0:01:13And what we discover is really surprising and really unsettling.
0:01:15 > 0:01:17It overturns my entire way of how I think about my body.
0:01:17 > 0:01:19I'm not well!
0:01:22 > 0:01:23But after meeting this scientist
0:01:23 > 0:01:27and some cheesecake-eating rats, we found that the latest
0:01:27 > 0:01:34scientific research changed what we thought we knew about fat and sugar.
0:01:34 > 0:01:37Total opposite of I think what we would expect,
0:01:37 > 0:01:39what most doctors would expect,
0:01:39 > 0:01:41what most people in the street would expect.
0:01:43 > 0:01:46And it has the potential to do the same for you.
0:02:09 > 0:02:11I'm Dr Chris van Tulleken,
0:02:11 > 0:02:14and I'm a specialist in infectious disease.
0:02:19 > 0:02:23Here in Britain, fat's traditionally been seen as the major problem.
0:02:24 > 0:02:27When I trained as a doctor it was clear that fat was the enemy
0:02:27 > 0:02:29because it raises your cholesterol
0:02:29 > 0:02:32and it blocks up your arteries, causing strokes and heart attacks.
0:02:35 > 0:02:39Over in America, it's sugar that's under attack.
0:02:41 > 0:02:45I'm Dr Xand van Tulleken and my speciality is in tropical medicine.
0:02:52 > 0:02:55Now, in the States, sugar isn't just regarded as unhealthy -
0:02:55 > 0:02:57some people are even calling it toxic.
0:03:00 > 0:03:02So, who's right?
0:03:02 > 0:03:07It's a question that's fascinated us as doctors, and by a quirk
0:03:07 > 0:03:11of birth, we have a head start in getting to grips with it.
0:03:12 > 0:03:14Chris and I are identical twins,
0:03:14 > 0:03:16which means we're genetically the same,
0:03:16 > 0:03:20so we're in a really nice position to do an experiment on each other.
0:03:20 > 0:03:23Now, I live in New York so I get constant messages
0:03:23 > 0:03:25in the media about how fat is good for you and sugar is
0:03:25 > 0:03:30really the enemy, so I'm going to go on a high fat, low sugar diet.
0:03:30 > 0:03:32And although in Britain we do get this message,
0:03:32 > 0:03:36it's not as pervasive, and I'm convinced if I go on a low fat,
0:03:36 > 0:03:38high sugar diet, I will stay healthy.
0:03:38 > 0:03:42So who's right? The Americans who think that sugar is really toxic?
0:03:42 > 0:03:45Or the British, who think that fat is the deadly ingredient?
0:03:52 > 0:03:55We're going on extreme diets based on the sort of techniques used
0:03:55 > 0:03:57in scientific research,
0:03:57 > 0:04:01although we are a rather unscientific sample of just two.
0:04:03 > 0:04:05We want to know what they do to your weight and how
0:04:05 > 0:04:09they affect lifestyle diseases like heart problems and diabetes.
0:04:10 > 0:04:13Nutritionist Amanda Ursell is on hand to make sure
0:04:13 > 0:04:17we get it right, and that it's edible.
0:04:17 > 0:04:19If we kick off with Chris.
0:04:19 > 0:04:21- Chris, you are on the high sugar diet.- Yeah. I can see that.
0:04:21 > 0:04:24People tend to think of sugar as this,
0:04:24 > 0:04:27the white stuff in the bowl, but actually all of this food
0:04:27 > 0:04:29ultimately gets broken down into blood sugar.
0:04:29 > 0:04:33So, you are allowed bread and bagels, pasta, rice,
0:04:33 > 0:04:35potatoes, any description of breakfast cereals.
0:04:35 > 0:04:38- And what's this? - That's, er, a fizzy drink.
0:04:38 > 0:04:40And you can have some fruit and veg.
0:04:40 > 0:04:42Well, you can have unlimited fruit and veg.
0:04:42 > 0:04:45And they've all got sugar and none of these... these foods have any fat, do they?
0:04:45 > 0:04:50It's designed to be very low fat and it's a high carb sugary diet,
0:04:50 > 0:04:52and that's what you can live on for the next month.
0:04:52 > 0:04:54For Xand, this is your bit here.
0:04:54 > 0:04:58Basically, you can have cheese, you can have meat, you can
0:04:58 > 0:05:01have steak, you can have burgers, it's chicken with the skin on,
0:05:01 > 0:05:04you can have double cream in your coffee, you can have mayonnaise...
0:05:04 > 0:05:07- The kind of thing you would do. - But you're not allowed any fruit,
0:05:07 > 0:05:09and you're not allowed very much of this veggie stuff at all.
0:05:09 > 0:05:13My problem is that I'm not going to have a poo for a month, am I?
0:05:13 > 0:05:15Well, there are disadvantages.
0:05:15 > 0:05:17Firstly, your girlfriend doesn't want to kiss you
0:05:17 > 0:05:18because you have bad breath.
0:05:18 > 0:05:20Constipation, yes, you're right.
0:05:20 > 0:05:22I'm getting almost no fibre in any of this, am I?
0:05:22 > 0:05:23Very limited fibre.
0:05:23 > 0:05:26I think I'm going to be craving a bowl of fresh greens
0:05:26 > 0:05:28by the end of a few days.
0:05:28 > 0:05:29I'm sure you are.
0:05:35 > 0:05:37What do you think, Xand? I mean, I feel like you got the better deal.
0:05:37 > 0:05:39It's difficult cos I'm going to have bad breath
0:05:39 > 0:05:41- and I'm not going to poo.- Mm.
0:05:41 > 0:05:43But I get to have bacon and eggs for breakfast.
0:05:43 > 0:05:47Just to be absolutely clear, we can both eat as much as we want
0:05:47 > 0:05:49of the things on our bit of the table?
0:05:49 > 0:05:51Yeah. That's what we want you to do.
0:06:02 > 0:06:05These diaries are going to be quite hard to stick to,
0:06:05 > 0:06:06so we're going to film them.
0:06:06 > 0:06:09We're going to make video diaries using our phones.
0:06:09 > 0:06:13So at least for the duration of the video diaries, Xand won't be able
0:06:13 > 0:06:15to be shovelling carbohydrate into his mouth.
0:06:15 > 0:06:20Just woken up, and what I feel like is a massive stack of pancakes,
0:06:20 > 0:06:21with maple syrup.
0:06:21 > 0:06:25The point is, if I have to tell into my phone every day
0:06:25 > 0:06:29what the experience is, I can't lie.
0:06:29 > 0:06:33- Keeps us honest.- Yeah. That's the plan.
0:06:33 > 0:06:36What we're going to do now is sample how much oxygen your body consumes.
0:06:41 > 0:06:44Food is, of course, the fuel that powers our bodies.
0:06:44 > 0:06:50But just how it does that is subject to complex metabolic processes.
0:06:53 > 0:06:59Dr Richard MacKenzie studies how these processes influence diseases like diabetes.
0:07:00 > 0:07:04It's long been thought that eating too much fat can make us fatter,
0:07:04 > 0:07:08and that saturated fat can raise our cholesterol.
0:07:08 > 0:07:10High amounts of cholesterol are quite bad for us.
0:07:10 > 0:07:14They block our arteries and that blocks blood supply
0:07:14 > 0:07:15to the brain and heart,
0:07:15 > 0:07:17so that's quite dangerous.
0:07:17 > 0:07:21Eating or drinking sugar, on the other hand, releases insulin,
0:07:21 > 0:07:24a hormone that regulates our blood sugar.
0:07:24 > 0:07:27Eating too much sugar can make us fat,
0:07:27 > 0:07:29and could potentially lead to diabetes.
0:07:30 > 0:07:34We're going to be checking to see if our cholesterol and insulin levels
0:07:34 > 0:07:37go up or down over the next month.
0:07:37 > 0:07:40What's nice about this experiment, it's not a big experiment,
0:07:40 > 0:07:42but we're well-controlled,
0:07:42 > 0:07:46- and so we really should get a robust answer from this.- Yeah.
0:07:46 > 0:07:49OK, gentlemen, what I need you to do is to pop behind the curtains
0:07:49 > 0:07:53and strip down into your boxer shorts, please.
0:07:53 > 0:07:57We're expecting these diets to have an impact on our bodies.
0:07:57 > 0:08:00And one thing we're focusing on are changes not to just to fat,
0:08:00 > 0:08:02but also to muscle.
0:08:04 > 0:08:07Shifting fat is good, but losing muscle isn't healthy.
0:08:07 > 0:08:09You do look very different to when I last saw you,
0:08:09 > 0:08:11and I must look different as well.
0:08:11 > 0:08:14Yeah, you've got a little bit fatter.
0:08:14 > 0:08:17The first time in a few years we look a bit like twins.
0:08:17 > 0:08:20OK, gents, we'll just go for the bod pod now,
0:08:20 > 0:08:22I can see you're both a little cold.
0:08:22 > 0:08:23It's freezing in here.
0:08:23 > 0:08:25I feel a bit underdressed.
0:08:26 > 0:08:29MACHINE: It is important to remove any jewellery,
0:08:29 > 0:08:31shoes or eyeglasses before weighing.
0:08:31 > 0:08:32Here we go.
0:08:32 > 0:08:36Enter the bod pod, then close the door to begin test.
0:08:39 > 0:08:43This machine measures the ratio of fat to muscle.
0:08:43 > 0:08:46So Richard, we know that being fat isn't good for you, but why do
0:08:46 > 0:08:50we need all this fancy equipment to measure it so precisely?
0:08:50 > 0:08:53It's to help improve our understanding of exactly what
0:08:53 > 0:08:57increased body fat is doing, and we know that it's
0:08:57 > 0:09:00linked to a number of diseases that reduce our life expectancy.
0:09:00 > 0:09:03So things like cancer, diabetes, heart disease, strokes,
0:09:03 > 0:09:05hypertension, to name just a few,
0:09:05 > 0:09:08all are related to an increase in body fat.
0:09:09 > 0:09:13- It's the same noise as the Batmobile canopy coming out.- Mm.
0:09:13 > 0:09:15Close the door to begin test.
0:09:18 > 0:09:21And now we freeze him and send him into outer space.
0:09:21 > 0:09:22Yeah, that's the plan.
0:09:23 > 0:09:27So we've got the results from the body composition test.
0:09:27 > 0:09:29So can we try and guess? Before you tell us, can we try and guess?
0:09:29 > 0:09:33- Please do.- I think I'm 25%.
0:09:35 > 0:09:38I feel like someone who almost a quarter of their body is fat,
0:09:38 > 0:09:40that's how I feel.
0:09:42 > 0:09:47You're pretty much spot-on, you're 26.7% body fat.
0:09:47 > 0:09:49Spot-on, but slightly more than spot-on.
0:09:50 > 0:09:53Good news for Chris is, he's 22% body fat.
0:09:53 > 0:09:56Oh, so we're pretty similar. Oh, that's quite good, actually.
0:09:56 > 0:09:58I mean I think, you know, there is going...you know, he...
0:09:58 > 0:10:02- So am I overweight?- Um, well, we'd have to look at your BMI for that.
0:10:02 > 0:10:04Don't pull the punch. Yes.
0:10:04 > 0:10:06- A little.- You're a quarter fat!
0:10:06 > 0:10:10- Look, Richard's being so nice about it!- "A little,
0:10:10 > 0:10:12"I mean, we couldn't - we'd need to look at the chart."
0:10:12 > 0:10:15All right, all right, I get the message, I get the message.
0:10:15 > 0:10:16- And he's OK, is he?- A fraction over,
0:10:16 > 0:10:20um, but certainly on the healthier side of 20, 22.6%.
0:10:20 > 0:10:21I'm letting you down.
0:10:21 > 0:10:23You're letting your genes down.
0:10:23 > 0:10:25Yeah, sorry about that.
0:10:29 > 0:10:34I'm eating a little piece of turkey rolled up in a piece of cheese.
0:10:34 > 0:10:37I'm eating everything with my fingers now!
0:10:43 > 0:10:46We're two weeks into the diets, and we now want to start
0:10:46 > 0:10:49measuring how fat and sugar are affecting our bodies.
0:10:53 > 0:10:57And the place we want to start is with our brains.
0:10:58 > 0:11:01Everything goes through your brain, every decision you make,
0:11:01 > 0:11:03every action you take.
0:11:03 > 0:11:04So it'd be pretty important to know
0:11:04 > 0:11:09if cutting out fat or sugar affected how well your brain worked.
0:11:20 > 0:11:23At some point, we've all felt the pressure of mental stress
0:11:23 > 0:11:28and tension, but how does what you eat effect how you deal with it?
0:11:31 > 0:11:35And there are fewer more cognitively demanding environments
0:11:35 > 0:11:36than a city day trading room.
0:11:39 > 0:11:43So, we're going to put our diets to an extreme mental test
0:11:43 > 0:11:46by becoming stock traders for the day.
0:11:48 > 0:11:51Chris, on his high sugar diet, is in London,
0:11:51 > 0:11:55and I'm on my high fat diet in New York.
0:11:56 > 0:12:00So Chris, do you have any sense that you're going to be any good at this?
0:12:00 > 0:12:02It is like the Matrix.
0:12:02 > 0:12:04I'm looking at a financial horror show, this is just a mess.
0:12:04 > 0:12:06I mean, no wonder the economy collapsed.
0:12:06 > 0:12:08How could anyone understand?
0:12:08 > 0:12:12OK, so that we have a bit of help, JJ is going to give us a hand, OK?
0:12:12 > 0:12:15- JJ.- Hey, Chris, you've got to have a better attitude going in, buddy,
0:12:15 > 0:12:17you're a smart guy, it's not that hard.
0:12:17 > 0:12:18X axis, Y axis, it's...
0:12:18 > 0:12:21It's buy high, sell low, yeah?
0:12:21 > 0:12:23Er, buy low, sell high.
0:12:23 > 0:12:24The other way.
0:12:25 > 0:12:28OK, trade, and right there you see a bid.
0:12:28 > 0:12:33After a quick lesson with JJ, we're let loose on US-based
0:12:33 > 0:12:37TD Ameritrade's paper money application, and we've got
0:12:37 > 0:12:41100,000 dollars of pretend money to play with.
0:12:41 > 0:12:42Yeah.
0:12:42 > 0:12:45It was a pleasure, guys. Chris, good luck. Xand, good luck.
0:12:45 > 0:12:47May the best twin win.
0:12:47 > 0:12:50- Right.- And thank you very much, fellas.
0:12:54 > 0:12:55I can buy a bit of that.
0:12:55 > 0:12:57I'm going to buy some more companies now.
0:12:57 > 0:12:59I'm into it now.
0:12:59 > 0:13:02Ten of oil, light sweet crude.
0:13:02 > 0:13:07If the oil comes up then I will have made a bunch of money.
0:13:09 > 0:13:12OK, so now the pressure's on cos I've spent all my money.
0:13:12 > 0:13:17'Watching closely in the background is Professor Robin Kanarek.
0:13:17 > 0:13:19'She studies the effects of diet on cognition,
0:13:19 > 0:13:22'and she thinks I might be in for a hard time.'
0:13:25 > 0:13:27Don't know what any of this means.
0:13:27 > 0:13:31This is an extraordinarily difficult task because there's many
0:13:31 > 0:13:35different aspects of cognition that have to be involved.
0:13:35 > 0:13:42He has to first pay attention, then he has to remember what he's done.
0:13:42 > 0:13:45What I can't remember is how many I bought and how many I sold.
0:13:45 > 0:13:47And then he has to make decisions,
0:13:47 > 0:13:49what we call executive processing,
0:13:49 > 0:13:52he has to decide whether to buy or sell.
0:13:52 > 0:13:55So he's got multiple things that are going on at the same time.
0:13:57 > 0:13:58Oh, no, I bought loads of them.
0:14:01 > 0:14:03See, now I've got negative money,
0:14:03 > 0:14:06and no way of getting back out of the hole.
0:14:10 > 0:14:13My problem is that being on a high fat diet could limit
0:14:13 > 0:14:14the fuel for my brain.
0:14:16 > 0:14:18I'm really stuck on this now.
0:14:23 > 0:14:26Glucose is the primary fuel of the brain
0:14:26 > 0:14:27and the best fuel for the brain.
0:14:27 > 0:14:29Since he's been on a low carbohydrate diet,
0:14:29 > 0:14:32almost eating no carbohydrates,
0:14:32 > 0:14:35his stores of glucose in the body are going to be very low.
0:14:36 > 0:14:39Um, and therefore I think as time goes on, he may be having
0:14:39 > 0:14:42more difficulty with the task.
0:14:44 > 0:14:48And I'm short of glucose on my extreme high fat diet.
0:14:49 > 0:14:52But the body has a back-up plan.
0:14:52 > 0:14:56It can turn fat into energy compounds called ketones,
0:14:56 > 0:14:58but they aren't as efficient.
0:14:59 > 0:15:03In normal everyday life, that's not a problem.
0:15:03 > 0:15:06But when you need to think really hard, it can be.
0:15:07 > 0:15:11I've got the initials in head and I can't remember what they stand for.
0:15:11 > 0:15:13Then I've got to try and remember something about the companies.
0:15:15 > 0:15:19The professor's research indicates that without enough carbohydrate
0:15:19 > 0:15:23in your diet, your memory can be significantly compromised.
0:15:23 > 0:15:28There are certain parts of the brain that use carbohydrates, particularly for memory,
0:15:28 > 0:15:33and if they're aren't getting enough glucose, then they can not function properly.
0:15:36 > 0:15:39Getting Exile at 97 dollars 29.
0:15:40 > 0:15:43Over in London, things are markedly different.
0:15:44 > 0:15:49Chris on his high sugar diet is more alert, has more energy,
0:15:49 > 0:15:51and has a significantly better memory.
0:15:52 > 0:15:57When I'm thinking hard I can really feel inside my head
0:15:57 > 0:15:59brainwork going on, and this is very brain-heavy,
0:15:59 > 0:16:02it's remembering loads of numbers, remembering loads of initials,
0:16:02 > 0:16:05and learning a whole new language of bidding and asking.
0:16:05 > 0:16:07So this screen means everything's going green
0:16:07 > 0:16:11so everything's going up, so you just have to hope that continues.
0:16:13 > 0:16:16I think I might be doing OK on my high sugar diet,
0:16:16 > 0:16:20because the brain consumes 60% of the sugars in your blood.
0:16:20 > 0:16:24For people who are on diets that have complex carbohydrates,
0:16:24 > 0:16:27er, whole grains, fruits and vegetables,
0:16:27 > 0:16:30there's a lot of studies that show at least on a short-term basis
0:16:30 > 0:16:35that having a high carbohydrate diet will facilitate memory.
0:16:35 > 0:16:36It's such fun.
0:16:37 > 0:16:40I can see why these guys get really into it.
0:16:41 > 0:16:44It's the end of the test, so who won?
0:16:44 > 0:16:46I can't remember what I wanted to do,
0:16:46 > 0:16:50let alone the numbers and letters I needed to do it.
0:16:50 > 0:16:51I'm not cut out for this.
0:16:51 > 0:16:54Maybe Chris'll have done better.
0:16:54 > 0:16:57So Xand made...Xand made essentially 300 dollars profit
0:16:57 > 0:17:00and I've made over 800 dollars profit.
0:17:00 > 0:17:02So I absolutely thrashed him,
0:17:02 > 0:17:05and I tell you what, I could not have done that if I'd been
0:17:05 > 0:17:09feeling hungry or wanting something I couldn't have, like some sugar,
0:17:09 > 0:17:12and a big carb breakfast is what meant I could do that.
0:17:16 > 0:17:19Scientists are now beginning to understand how certain parts
0:17:19 > 0:17:22of our memory are affected by carbohydrates.
0:17:25 > 0:17:28On my high sugar diet I'm eating all kinds of carbs from starches
0:17:28 > 0:17:30to grains, vegetables to fruit.
0:17:36 > 0:17:39But no matter what form the carbohydrates come in,
0:17:39 > 0:17:41it's all broken down in my gut
0:17:41 > 0:17:44into single sugar molecules, like fructose or glucose.
0:17:51 > 0:17:53And the effect of these molecules on our bodies
0:17:53 > 0:17:56that's at the core of why some scientists,
0:17:56 > 0:17:59particularly in America, argue that sugar's bad for you.
0:18:03 > 0:18:05So Xand's in San Francisco,
0:18:05 > 0:18:09to meet one of the researchers who's led the charge against sugar.
0:18:16 > 0:18:20He's seeing Dr Robert Lustig, who's convinced that the way fructose
0:18:20 > 0:18:25and glucose work in our bodies leads to all kinds of health problems.
0:18:25 > 0:18:28Robert, do you want to pause in the doughnut store
0:18:28 > 0:18:31- and get a bucket full? - I...I... We'll talk about it later.
0:18:38 > 0:18:42For him, glucose and fructose are dangerous for different reasons.
0:18:43 > 0:18:46First of all, fructose.
0:18:46 > 0:18:49Turns out, only the liver can metabolise fructose,
0:18:49 > 0:18:54and you have a limit to how much you can metabolise, just like any drug.
0:18:54 > 0:18:57You have a threshold.
0:18:57 > 0:19:01If you go over that threshold, your liver has no choice
0:19:01 > 0:19:04but to take that extra energy that's been delivered to it
0:19:04 > 0:19:06and turn it into liver fat,
0:19:06 > 0:19:09because that's the way the way the liver gets rid of extra energy.
0:19:09 > 0:19:12So you drink a bottle of soda, some of it you can metabolise,
0:19:12 > 0:19:14but the rest of it has to become liver fat?
0:19:14 > 0:19:15That's right.
0:19:19 > 0:19:23And that liver fat can have damaging consequences for your health.
0:19:23 > 0:19:27It can make you more liable to heart disease, strokes, or diabetes.
0:19:29 > 0:19:33But according to Dr Lustig, that's just half the problem with sugar.
0:19:35 > 0:19:37The glucose molecule activates insulin,
0:19:37 > 0:19:40the hormone that controls blood sugar.
0:19:40 > 0:19:44But Lustig believes insulin does a whole lot more.
0:19:45 > 0:19:49Insulin shunts sugar to fat. The more insulin, the more fat.
0:19:49 > 0:19:53Well, guess what? The more insulin, the more disease, too.
0:19:53 > 0:19:58- OK.- And insulin is really the lynchpin in this whole story,
0:19:58 > 0:20:01because whether you gain weight and whether you get sick
0:20:01 > 0:20:04has everything to do with what your insulin does,
0:20:04 > 0:20:07and if you can keep your insulin level down,
0:20:07 > 0:20:09then you won't drive energy into fat,
0:20:09 > 0:20:11you have a chance to lose weight,
0:20:11 > 0:20:13you won't be making your arteries thicker,
0:20:13 > 0:20:15you have a chance for your blood pressure to come down,
0:20:15 > 0:20:17and this is what we've seen,
0:20:17 > 0:20:19is, "it's the insulin, stupid."
0:20:20 > 0:20:23It's known as the hormone hypothesis,
0:20:23 > 0:20:27because fat cells respond to the release of insulin by holding
0:20:27 > 0:20:30onto fat, and making more of it.
0:20:39 > 0:20:42In general, the studies that support the theory about fructose
0:20:42 > 0:20:46only looked at diets with unrealistically high levels of fructose.
0:20:47 > 0:20:50Much more than the average person consumes.
0:20:51 > 0:20:54So I'm not yet convinced about fructose.
0:20:56 > 0:20:58And as for the insulin hypothesis,
0:20:58 > 0:21:01the comprehensive study hasn't been done yet.
0:21:01 > 0:21:04So like most scientists in Britain,
0:21:04 > 0:21:06I'm pretty sceptical about these claims.
0:21:11 > 0:21:13I'm three weeks into my high fat diet
0:21:13 > 0:21:16and I'm really starting to miss carbohydrates.
0:21:17 > 0:21:21I've got on the plane very early,
0:21:21 > 0:21:24which means I can try and eat my burger quickly
0:21:24 > 0:21:25before anyone sits next to me.
0:21:25 > 0:21:28It's really hard not to eat the French fries.
0:21:33 > 0:21:35So I'm all done.
0:21:35 > 0:21:37This is what remains.
0:21:44 > 0:21:46But even though I couldn't eat the carbs,
0:21:46 > 0:21:48I wasn't ravenous after my meal.
0:21:49 > 0:21:51What I really want to know is
0:21:51 > 0:21:54if that has anything to do with the amount of fat in my diet?
0:22:03 > 0:22:05To try and understand what's happening,
0:22:05 > 0:22:07Xand has to fly back to Britain...
0:22:09 > 0:22:12Right, boys. We want you to do something...
0:22:12 > 0:22:15..where Amanda Ursell has set up what she calls
0:22:15 > 0:22:17a hunger experiment.
0:22:23 > 0:22:27We start the day eating the same amount of calories for breakfast.
0:22:33 > 0:22:37Xand has a plateful of fat calories, but mine is chock full of sugar.
0:22:40 > 0:22:44Three hours later, we're offered lunch.
0:22:46 > 0:22:49And this is where it gets really interesting.
0:22:50 > 0:22:55Because now, Amanda can test whether or not eating fat or sugar
0:22:55 > 0:22:59has had any effect on how hungry we were.
0:22:59 > 0:23:01Well, I'm jotting down what you're having,
0:23:01 > 0:23:03so I'm going to count all the calories that you're going
0:23:03 > 0:23:06to have, so I know exactly what's on the plate, so, there we are.
0:23:06 > 0:23:10So will we eat the same number of calories like we did at breakfast?
0:23:10 > 0:23:14- I'm going to start with this soup.- OK, the soup.
0:23:14 > 0:23:18- Come on, come on.- Go on, then - off you go.
0:23:18 > 0:23:22Start eating. I'm going to work all this out for you.
0:23:22 > 0:23:27We both start hungry, but that doesn't last for long.
0:23:31 > 0:23:33Do you think I'm going to be able to eat all that?
0:23:33 > 0:23:37- No, no.- Delicious though this all looks, I'm not really enjoying it.
0:23:39 > 0:23:41All right, what else can I have?
0:23:41 > 0:23:42We've got some pasta.
0:23:42 > 0:23:44- Pasta.- Yeah.
0:23:44 > 0:23:48But is how hungry we feel just down to the calories we consume?
0:23:52 > 0:23:55It's like I just don't want any more of that.
0:23:55 > 0:23:57My brain has just said, "No, that's it, that's all you need."
0:23:57 > 0:24:01- Can I take that? I need to measure what you've left.- Absolutely.
0:24:02 > 0:24:07Or could it be the macronutrients in the meals, fat or sugar,
0:24:07 > 0:24:09that are governing how hungry we feel?
0:24:10 > 0:24:14- On this diet I can still eat to shame.- Really?
0:24:14 > 0:24:18To the moment at which I hate myself more than I want to keep eating.
0:24:20 > 0:24:23Can you get that whole meringue in your mouth at once?
0:24:30 > 0:24:31So we've got the results now.
0:24:34 > 0:24:36Later, Amanda gets busy with her calculator
0:24:36 > 0:24:39and tots up the final calorie count.
0:24:39 > 0:24:42OK, Xand, you're on the high fat diet, you had 825 calories.
0:24:42 > 0:24:45- That's quite a lot. - Yes, that's a big meal.
0:24:45 > 0:24:49Yeah, but you, Chris, on your carb blowout, you had, er 1,250 calories.
0:24:49 > 0:24:52- Whoa!- That's...that's half your calories for the day right there.
0:24:52 > 0:24:55- That's half my whole day's calories in a single sitting.- Yeah.
0:24:55 > 0:24:59For me, the interesting thing is, I ate more food than you,
0:24:59 > 0:25:02so calories do not necessarily make you feel full,
0:25:02 > 0:25:05and I was then hungrier quicker,
0:25:05 > 0:25:07so this really simple idea
0:25:07 > 0:25:09that we kind of learn that if you feel hungry
0:25:09 > 0:25:12you eat a meal and then you stop feeling hungry,
0:25:12 > 0:25:14even that is not really true.
0:25:14 > 0:25:17You can eat an enormous meal and end up being hungrier than the person
0:25:17 > 0:25:20who ate...you know, you ate almost the number of calories I did.
0:25:20 > 0:25:22What's going on there, then? Why is that?
0:25:22 > 0:25:24There's quite a big body of research that suggests that
0:25:24 > 0:25:26high protein diets make you feel fuller.
0:25:26 > 0:25:28It's the protein that's making me feel full?
0:25:28 > 0:25:30You don't really eat high fat on its own,
0:25:30 > 0:25:32you don't eat butter on its own or glug down olive oil on its own.
0:25:32 > 0:25:34Xand might.
0:25:34 > 0:25:37It comes with protein and makes you feel fuller than the carbohydrates.
0:25:37 > 0:25:39That's probably number 1.
0:25:42 > 0:25:44But it's more than that.
0:25:44 > 0:25:47Protein and sugar have very different effects on ghrelin
0:25:47 > 0:25:49the hunger hormone.
0:25:49 > 0:25:54The more ghrelin you have in your body, the hungrier you'll feel.
0:25:55 > 0:25:59Protein suppresses ghrelin for longer than sugar.
0:26:02 > 0:26:06The problem with sugar is that it's an easy source of calories,
0:26:06 > 0:26:08and that can make you fat.
0:26:09 > 0:26:13But you can end up eating fewer calories on a high fat diet
0:26:13 > 0:26:16because of the interaction with ghrelin.
0:26:18 > 0:26:20Not all fats are the same,
0:26:20 > 0:26:22and fortunately on my diet I'm mostly on the good stuff.
0:26:22 > 0:26:26I'm eating lots of monosaturated and polyunsaturated fats,
0:26:26 > 0:26:31the kind of thing you find in eggs, olive oil, and oily fish.
0:26:31 > 0:26:33And that's all good for you.
0:26:33 > 0:26:35Now, I'm also eating quite a lot of saturated fat,
0:26:35 > 0:26:39which is the kind of thing you find in foods like meat and cheese.
0:26:39 > 0:26:41Now this stuff you're not recommended to have more
0:26:41 > 0:26:44than 30 grams a day because it raises your LDL,
0:26:44 > 0:26:47your bad cholesterol, but recently an increasing
0:26:47 > 0:26:50number of scientists are saying this may not actually be true.
0:26:50 > 0:26:53But there is no debate about trans fats.
0:26:53 > 0:26:56Now, trans fats are found in a wide range of manufactured foods
0:26:56 > 0:27:00like cakes and cookies, things like this, and they're not good for you.
0:27:00 > 0:27:02And what they do is they not only raise your LDL,
0:27:02 > 0:27:07your bad cholesterol, but they lower your HDL, your good cholesterol.
0:27:07 > 0:27:10Fortunately, on my diet I'm not allowed to have any of them.
0:27:18 > 0:27:23A gram of fat also has over twice as many calories as a gram of sugar.
0:27:26 > 0:27:30And our bodies turn dietary fats into body fat more easily
0:27:30 > 0:27:32than it does with sugar.
0:27:33 > 0:27:37Ultimately, of course, fat and sugar are sources of energy.
0:27:38 > 0:27:43So what we really want to know is how they work to fuel our bodies.
0:27:43 > 0:27:46It's now going to get personal and painful.
0:27:48 > 0:27:52What we're going to do is we'll have five minutes steady peddling away,
0:27:52 > 0:27:55I'm going to talk to you, I want to keep a nice conversation going,
0:27:55 > 0:27:58and then we're just going to start ramping it up a little bit.
0:27:58 > 0:28:01We set up another test, this time on a bike.
0:28:02 > 0:28:05This is very fun, I haven't used one of these before.
0:28:05 > 0:28:07Have you not? Oh, you're going to hate it soon.
0:28:07 > 0:28:09We've recruited Nigel Mitchell
0:28:09 > 0:28:13from the first ever British Tour de France winning cycling team
0:28:13 > 0:28:14to help us.
0:28:14 > 0:28:17- Perfect, perfect, perfect. Just nice.- Keeping up so far.
0:28:20 > 0:28:23This is the first exercise of any kind we've done in our diet,
0:28:23 > 0:28:26and we've not eaten for 12 hours.
0:28:26 > 0:28:29Your cadence looks nice. Drop a gear.
0:28:32 > 0:28:35We're 15 minutes into an hour-long session.
0:28:35 > 0:28:37Nigel wants to completely exhaust us.
0:28:39 > 0:28:43- Ramp this up a little bit to 18mph now.- Drop a gear?- Drop a gear.
0:28:45 > 0:28:47Yeah, we're starting to work a bit more now.
0:28:49 > 0:28:52It's the first step in a particularly sadistic experiment,
0:28:52 > 0:28:56to see if fat or sugar is the best macronutrient for exercise.
0:29:01 > 0:29:04So, how much difference does the kind of nutrition science
0:29:04 > 0:29:06you're doing make to a team?
0:29:06 > 0:29:08I want to use foods to fuel them,
0:29:08 > 0:29:10I want to use foods for them to recover.
0:29:10 > 0:29:12So the foods that we give the guys
0:29:12 > 0:29:15is a mixture of bars and gels and protein.
0:29:15 > 0:29:17Breakfast, we use a lot of porridge.
0:29:17 > 0:29:19Now you can't get porridge on the continent,
0:29:19 > 0:29:22so for the Tour de France and all this we actually buy
0:29:22 > 0:29:25the porridge oats in this country and we take them out there.
0:29:25 > 0:29:28And last year it were about three weeks before the tour
0:29:28 > 0:29:30and I go around my local supermarket
0:29:30 > 0:29:32and I've got all my Sky kit on cos I'm working, and I've
0:29:32 > 0:29:36got a trolley full of porridge oats, I've got about 80kg of trolley oats.
0:29:36 > 0:29:39I put them on the conveyor belt and we take them through,
0:29:39 > 0:29:41and the woman on the conveyor belt,
0:29:41 > 0:29:43woman on the till just brings you down to Earth, she says,
0:29:43 > 0:29:46said to me, "So do you work in a care home or something, you know,
0:29:46 > 0:29:48"all this porridge oats that you've got?"
0:29:53 > 0:29:5645 minutes in, Nigel takes a blood sample.
0:29:59 > 0:30:03'The blood test confirm just how bad we feel.
0:30:03 > 0:30:07'Chris is burning sugar like crazy and his blood sugar levels
0:30:07 > 0:30:11'plummet from 4.7, where they were at the start of the test, to 2.7.
0:30:13 > 0:30:18'I'm faring better. My blood sugar has fallen by only about 25%.'
0:30:22 > 0:30:25This is doing exactly what we wanted it to do.
0:30:29 > 0:30:34Last minute, then, boys. Just keep it like this.
0:30:34 > 0:30:38'An hour of punishing exercise without food has pushed us to the
0:30:38 > 0:30:39'edge of our physical capabilities.'
0:30:42 > 0:30:44Yeah, I feel like I'm out of juice.
0:30:49 > 0:30:51'We're now both exhausted and empty,
0:30:51 > 0:30:56'which allows Nigel to test how fat and sugar fuel the body.'
0:30:56 > 0:31:00OK, boys, so we've done the hour on the turbo trainers at the top,
0:31:00 > 0:31:04we've pushed your blood sugars down, so you're just mild hypo...
0:31:04 > 0:31:08Get off! What we're going to do now is race up the hill.
0:31:08 > 0:31:12Now, we've got some food, so for Xander, we've got butter,
0:31:12 > 0:31:15so it's one pack of butter, please. Just one.
0:31:15 > 0:31:18And then I want you to take one in your pocket for eating
0:31:18 > 0:31:21on the way up, and then we've got a gel for you.
0:31:21 > 0:31:24- The same number of calories in the gel.- Roughly.
0:31:24 > 0:31:27We've got the same number of calories in the gel as the butter.
0:31:27 > 0:31:29But the gel is sugar.
0:31:29 > 0:31:32'There's nothing special about either the butter or the gel.
0:31:32 > 0:31:35'They're basically fat and sugar.'
0:31:35 > 0:31:38So, right, I want you to ride at my pace.
0:31:38 > 0:31:41I want us to control this, as we're going up there.
0:31:41 > 0:31:44A little bit easier on the gears. That's it, perfect.
0:31:44 > 0:31:45You're in the same gear.
0:31:45 > 0:31:48'Now it's time for the race up the hill, between fat in red
0:31:48 > 0:31:50'and sugar in blue.'
0:31:50 > 0:31:54When we turn right, we're going to start just lifting it slightly.
0:31:54 > 0:31:58- Are you OK?- Yeah, I'm all right. - Just push on a bit more, then.
0:31:59 > 0:32:04'We're climbing the iconic and steep Box Hill in Surrey.'
0:32:04 > 0:32:06'And in the next few seconds,
0:32:06 > 0:32:10'it's going to turn into a fat versus sugar race to the summit.'
0:32:10 > 0:32:13- What's your heart rates now, boys?- 177.
0:32:13 > 0:32:15154.
0:32:15 > 0:32:18Just keep next to each other, if you can.
0:32:18 > 0:32:21OK? Right, are you ready, both of you? Go!
0:32:24 > 0:32:27Keep it going. Keep it going.
0:32:31 > 0:32:34'In the race to the top, Chris soon speeds away from me.'
0:32:38 > 0:32:40He just keeps getting further away
0:32:40 > 0:32:45and I cannot make my legs go any faster.
0:32:45 > 0:32:48It's like I'm stuck in one gear.
0:32:53 > 0:32:57'With my heart rate pumping at 200 beats per minute,
0:32:57 > 0:33:00I just manage to get to the top.'
0:33:00 > 0:33:03Just looking at you two, you've got a big smile on your face.
0:33:03 > 0:33:06You won the King of the Mountains there, Chris.
0:33:06 > 0:33:09Xander, you bunked out. But this is the thing.
0:33:09 > 0:33:11This is what we're trying to show.
0:33:11 > 0:33:14When you're really trying to push it, your body needs the sugar.
0:33:14 > 0:33:18It needs the carbohydrates. I want to measure the sugars again.
0:33:21 > 0:33:247.1, your blood sugar now. 7.1.
0:33:26 > 0:33:29'Chris's blood sugars are so high because the sugar gel
0:33:29 > 0:33:32'he consumed half an hour ago is still pulsing through his body.
0:33:35 > 0:33:39'And that gave him the fuel to power his muscles up the hill.
0:33:40 > 0:33:44'But what about my blood sugar levels?'
0:33:44 > 0:33:465.1, now that's interesting.
0:33:46 > 0:33:51All we've given you to eat is fat and we can't convert fat into sugar.
0:33:51 > 0:33:54'Completely deprived of glucose,
0:33:54 > 0:33:58'our bodies have a dramatic way of making sugar.
0:33:58 > 0:34:02'Protein in the form of muscle converts into amino acids,
0:34:02 > 0:34:04'which are then turned into glucose
0:34:04 > 0:34:08'and that's pumped into the blood, raising blood sugar levels.
0:34:13 > 0:34:17'So there's no question you can power your body without sugar,
0:34:17 > 0:34:19'but there is a price to pay.'
0:34:19 > 0:34:23Your blood sugars going up has got to be coming from the protein.
0:34:23 > 0:34:25He's burning muscle to make sugar.
0:34:25 > 0:34:29- He's burning muscle to make sugar now.- I feel quite rubbish.
0:34:29 > 0:34:32This is the last state you'd want one of your athletes to be in.
0:34:32 > 0:34:35If we'd got one of our riders and they were in your state in the
0:34:35 > 0:34:40Tour de France then I'd be looking for a new job.
0:34:40 > 0:34:44So we had identical turbos, we've got identical bikes, we've got
0:34:44 > 0:34:47the same tyre pressure, so you're doing the same work...
0:34:47 > 0:34:49We've got effectively the same person.
0:34:49 > 0:34:52Effectively the same person genetically.
0:34:52 > 0:34:56The big difference is the diet that you've been following.
0:34:59 > 0:35:02What's amazing about that is I haven't eaten any carbohydrate
0:35:02 > 0:35:06in weeks and my body can still make enough sugar to get me up that hill.
0:35:06 > 0:35:08How have you done this?
0:35:08 > 0:35:12How have you turned your dreadful performance up that
0:35:12 > 0:35:16- hill into a kind of victory for fat? - I got here, didn't I?
0:35:16 > 0:35:19And... Yes, you did have normal carbohydrate, which is...
0:35:19 > 0:35:23It's a point for me because your body needs carbohydrates to exercise like that.
0:35:23 > 0:35:27And where are you getting the carbohydrate? From your muscles.
0:35:27 > 0:35:31So you do exercise like that all day, you'll actually lose muscle and keep your little belly cos you're
0:35:31 > 0:35:34- not turning that into carbs, are you?- All right.
0:35:34 > 0:35:36I'll beat you on the way down.
0:35:36 > 0:35:40- Yeah cos you're still fat! - HE CHUCKLES
0:35:52 > 0:35:55This meal, it should be so good...
0:35:55 > 0:35:59It's missing one essential ingredient.
0:36:01 > 0:36:02And that's fat.
0:36:02 > 0:36:04So it's totally joyless.
0:36:04 > 0:36:06It's just a rubbish end to my day.
0:36:12 > 0:36:15At last, the diets are over.
0:36:15 > 0:36:19And we're back at the lab to find out what effect fat
0:36:19 > 0:36:22and sugar have had on our weight and health.
0:36:23 > 0:36:27OK, chaps. What I need you to do is get stripped off like before.
0:36:27 > 0:36:32'We're with our old friend Richard McKenzie to be weighed and measured.'
0:36:33 > 0:36:35OK, no talking, no moving.
0:36:35 > 0:36:39'Starting, of course, with the machine that measures
0:36:39 > 0:36:42'the percentage of fat and muscle in our bodies.'
0:36:43 > 0:36:46OK, and you're up next.
0:36:46 > 0:36:50'..Then close the door to begin tests.'
0:36:50 > 0:36:55'And he's got some good news and unfortunately, some bad news for us,
0:36:55 > 0:37:00'beginning with the results for the high sugar diet.'
0:37:00 > 0:37:04- Chris, OK, you've lost 1kg of body mass.- Is that good?
0:37:04 > 0:37:09You've been eating as much as you want of junk for a month
0:37:09 > 0:37:11and you've lost a kilo.
0:37:11 > 0:37:13Yeah, it's not bad.
0:37:13 > 0:37:15Half of that has come from body fat
0:37:15 > 0:37:18and the other half has come from muscle mass.
0:37:18 > 0:37:22- Oh, really? So I have lost muscle as well?- Yes.- What about him?
0:37:22 > 0:37:25- I feel like I've lost weight. - You have.
0:37:25 > 0:37:29You've lost around 4kg of body mass.
0:37:29 > 0:37:32'On the high fat diet, Xand has lost more weight.
0:37:32 > 0:37:36'To be more accurate, 3.5 kilos in a month.'
0:37:36 > 0:37:38So, where has that weight loss come from?
0:37:38 > 0:37:422kg has come from muscle mass, 1.5 has come from fat mass.
0:37:42 > 0:37:44I've lost weight, which is great,
0:37:44 > 0:37:47and I've lost a legitimate 1.5 kilos of fat.
0:37:47 > 0:37:50In four weeks, that's really good.
0:37:50 > 0:37:52On the face of it, that's very good.
0:37:52 > 0:37:54Yeah, on the face of it,
0:37:54 > 0:37:58but you've lost 1.5 kilos of fat and you've lost 2 kilos of muscle.
0:37:58 > 0:38:01Your brother's right. We have to look at it in a bit more detail
0:38:01 > 0:38:05and losing body weight is an ideal goal in some circumstances,
0:38:05 > 0:38:09but you've lost 2kg of muscle mass and that isn't healthy.
0:38:09 > 0:38:11Why is it so bad to have lost these 2 kilos of muscle?
0:38:11 > 0:38:15If you lose muscle mass, with disease or ageing,
0:38:15 > 0:38:17you are more likely to visit the hospital more often
0:38:17 > 0:38:20and have a poor life expectancy.
0:38:20 > 0:38:22- Really?- Yes.- That bad?- Yes.
0:38:22 > 0:38:25That's a really important counterintuitive thing,
0:38:25 > 0:38:28I think, that we're going to lose weight, go on a diet, we don't
0:38:28 > 0:38:32think too much about exercise, and it can be really bad for you.
0:38:39 > 0:38:43'Nervously, we went through the same battery of tests as we did
0:38:43 > 0:38:48'a month ago. First, we checked our cholesterol.'
0:38:48 > 0:38:51'We thought that because Xand was eating so much fat on his diet,
0:38:51 > 0:38:53'his levels would be much higher.
0:38:53 > 0:38:56'What was amazing is that they were nearly exactly
0:38:56 > 0:39:00'the same as they were at the start of our diets.
0:39:00 > 0:39:03'In fact, there was little or no change for either of us.'
0:39:05 > 0:39:07One minute to finish.
0:39:10 > 0:39:12'Finally, we tested our insulin,
0:39:12 > 0:39:16'the hormone that regulates the level of sugar in your blood.'
0:39:16 > 0:39:18Urgh!
0:39:18 > 0:39:23'Naturally enough, on the high sugar diet, I went first.'
0:39:23 > 0:39:27Your body's ability to produce insulin improved.
0:39:27 > 0:39:30- That is the opposite... - Totally the opposite
0:39:30 > 0:39:33of I think what we would expect, most doctors would expect,
0:39:33 > 0:39:37what most people in the street would expect.
0:39:37 > 0:39:40Probably just got used to dealing with the sugar,
0:39:40 > 0:39:44the glucose intake and therefore, responding by producing insulin.
0:39:44 > 0:39:47A bit like if I'd been drinking a lot for the month,
0:39:47 > 0:39:50my liver would up-regulate the enzymes to deal with the alcohol.
0:39:50 > 0:39:52It's almost the same thing.
0:39:52 > 0:39:55Because I've been eating loads of sugar,
0:39:55 > 0:39:59- I've become better at managing it. - You're better at producing insulin.
0:39:59 > 0:40:01Is that good or not?
0:40:01 > 0:40:03Um...
0:40:03 > 0:40:05In the short term, it is good, but long term,
0:40:05 > 0:40:08it might produce a problem.
0:40:08 > 0:40:11'An unexpected result for me.
0:40:11 > 0:40:16'But what about Xand on the high fat diet?'
0:40:16 > 0:40:18What is worrying is your body is not responding to
0:40:18 > 0:40:20insulin as well as it did.
0:40:20 > 0:40:25If you eat too much fat, that can stop your body responding to
0:40:25 > 0:40:29insulin and it also can tell your body to produce more glucose.
0:40:29 > 0:40:33So how serious is this? It's only a month. Is this a big difference that you're seeing?
0:40:33 > 0:40:35Actually, it is a big difference.
0:40:35 > 0:40:39What we've seen is your blood glucose has climbed from 5.1,
0:40:39 > 0:40:43which it was before the diet, which wasn't great to start with,
0:40:43 > 0:40:47but still in a healthy range, to 5.9.
0:40:47 > 0:40:51You're only 0.2 away from being pre-diabetic.
0:40:51 > 0:40:53Wow!
0:40:53 > 0:40:56In a month, I've done myself some proper damage.
0:40:56 > 0:40:59- This isn't good for me at all. - It's not good for you.
0:40:59 > 0:41:02That's the first thing. You should stop that diet.
0:41:07 > 0:41:10Eventually, your body will stop producing insulin
0:41:10 > 0:41:11if you carry on down this path.
0:41:11 > 0:41:13I've been on a no-sugar diet
0:41:13 > 0:41:16and I just would have thought I'd be making less insulin
0:41:16 > 0:41:20and needing less insulin. You're saying I'm making more insulin,
0:41:20 > 0:41:22my body isn't reacting to it as well
0:41:22 > 0:41:24and I'm well down the road to diabetes,
0:41:24 > 0:41:26which is, which is bad news.
0:41:26 > 0:41:28It's bad news, you're heading that way.
0:41:35 > 0:41:37So I thought if you eat lots of sugar,
0:41:37 > 0:41:39you make lots of insulin and that's bad,
0:41:39 > 0:41:43but it turns out me eating lots of fat makes my body insulin-resistant
0:41:43 > 0:41:45so I make more insulin and that's worse.
0:41:45 > 0:41:47So I'm...I'm doing really...
0:41:47 > 0:41:50Like, I'm close to being diabetic now, I'm not...I'm not well!
0:41:50 > 0:41:53I mean, was wrong too. Like I...so I thought, "Well, I'm having coffee,
0:41:53 > 0:41:55"I can't have my cream in it, so I'll put in lots of sugar,"
0:41:55 > 0:41:58so I ate so much more sugar that I normally would...
0:41:58 > 0:42:02- And I'd have thought that would make you diabetic or close to it. - That's...that's, I think we all,
0:42:02 > 0:42:05that's the received wisdom of becoming diabetic is about eating sugar.
0:42:05 > 0:42:09When are we ever going to learn that if you...it's never about one thing.
0:42:09 > 0:42:11We say, "Oh, it must be fat or it must be sugar..."
0:42:11 > 0:42:14No, it is ALWAYS more complicated than that. Always
0:42:14 > 0:42:17It's like a really basic rule in life, isn't it? If someone
0:42:17 > 0:42:20is selling you one simple solution to a problem that everyone has,
0:42:20 > 0:42:22- it probably isn't going to work.- No.
0:42:39 > 0:42:42As doctors, we know we have got to be careful
0:42:42 > 0:42:47about extrapolating too much from our own experience.
0:42:47 > 0:42:50Human physiology can be extremely complicated.
0:42:58 > 0:43:02Being on a low-fat or a low-carb diet yourself, you learn all kinds
0:43:02 > 0:43:05of things that you could never get from reading about it in a paper.
0:43:05 > 0:43:08You learn about the experience of being on it,
0:43:08 > 0:43:12whether or not it's fun, whether or not it's nasty, how it feels.
0:43:12 > 0:43:14But the numbers that you get from an experiment
0:43:14 > 0:43:17with just two people aren't definitive.
0:43:17 > 0:43:19They're interesting, but they don't tell you enough.
0:43:19 > 0:43:22To get definitive information from those numbers,
0:43:22 > 0:43:24you have to look at the experiments
0:43:24 > 0:43:27that are being done on thousands of people.
0:43:35 > 0:43:37Over the last few years,
0:43:37 > 0:43:39as the world's got fatter and more unhealthy,
0:43:39 > 0:43:42finding an answer to the fat-versus-sugar question
0:43:42 > 0:43:43has become even more pressing.
0:43:51 > 0:43:55One of Britain's leading nutritionists, Professor Susan Jebb,
0:43:55 > 0:43:58has been researching this for more than a decade.
0:43:58 > 0:44:01And she started with a simple observation.
0:44:01 > 0:44:03We've been looking at this for...for many years
0:44:03 > 0:44:06and I guess what I struggle with is the idea that,
0:44:06 > 0:44:09you know, people start off thin, or lean...
0:44:09 > 0:44:12- Uh-huh.- ..and at some point during their lives,
0:44:12 > 0:44:15many people end up gaining weight, becoming fat...
0:44:15 > 0:44:16This is me at the moment.
0:44:16 > 0:44:19And a proportion of those go on to become sick and they develop
0:44:19 > 0:44:24illnesses, like cardiovascular disease or...or diabetes.
0:44:26 > 0:44:28We're in no doubt about this link, that being fat makes
0:44:28 > 0:44:31a lot of people, not everyone, but a lot of people ill.
0:44:31 > 0:44:34Absolutely, increases your risk of heart disease,
0:44:34 > 0:44:35of cancer and of diabetes.
0:44:35 > 0:44:39- OK.- So is it something about their diet which alters that risk?
0:44:39 > 0:44:46We looked at um...at the amount of fat or carbs or indeed protein...
0:44:46 > 0:44:50'So she set up a series of long-running, comprehensive studies
0:44:50 > 0:44:53'to see what effects feeding people fat,
0:44:53 > 0:44:56'sugar and protein had on their health and well-being.'
0:44:56 > 0:44:59And more than that, we've tried to study the differences
0:44:59 > 0:45:03in these groups, so we've been interested in saturated fat...
0:45:03 > 0:45:06'She fed them bad fats - saturated fats,
0:45:06 > 0:45:09'and good fats - monounsaturated fats.
0:45:09 > 0:45:12'She did the same with carbohydrates,
0:45:12 > 0:45:15'feeding people low and high GI, whole grains and refined grains.'
0:45:18 > 0:45:22Maybe is about the fibre in the food or maybe is about sugar.
0:45:24 > 0:45:26'For ten years,
0:45:26 > 0:45:29'she conducted a series of detailed scientific studies
0:45:29 > 0:45:33'into which was worst - fat or sugar.'
0:45:33 > 0:45:35So I'm on tenterhooks, like, so what did you find?
0:45:35 > 0:45:39You know, the changes that we got were important,
0:45:39 > 0:45:40but they were quite modest.
0:45:40 > 0:45:46They were surprisingly small, much smaller than I was anticipating.
0:45:46 > 0:45:48And there are clear benefits
0:45:48 > 0:45:51of a little bit more monounsaturated fats,
0:45:51 > 0:45:54some benefits of low GI, some of more fibre,
0:45:54 > 0:45:58but I really don't think we could say that a diet
0:45:58 > 0:46:05which had some extreme composition was really a revolutionary answer.
0:46:08 > 0:46:13What her study showed was that changing fat or sugar on their own
0:46:13 > 0:46:14had a very small effect.
0:46:19 > 0:46:24Especially when compared to the effect of losing or gaining weight.
0:46:33 > 0:46:35So what is it that we're eating
0:46:35 > 0:46:38that's making us fatter and unhealthier?
0:46:38 > 0:46:43Unlikely as it may seem, the first clue in solving that puzzle
0:46:43 > 0:46:46might lie in this tempting tray of doughnuts.
0:46:51 > 0:46:53What I want you to do is look at this tray of doughnuts
0:46:53 > 0:46:57and think about which one you'd choose if you could have any of them.
0:46:57 > 0:46:59Got it?
0:46:59 > 0:47:00Now, this is like a card trick,
0:47:00 > 0:47:03I want you to remember the doughnut you chose and we're going to see
0:47:03 > 0:47:07if the people in New York choose the same one as you.
0:47:07 > 0:47:09All you have to do is choose a doughnut.
0:47:09 > 0:47:11Ah, it's easy.
0:47:18 > 0:47:20I'm going to find out if people in London
0:47:20 > 0:47:23have the same taste in doughnuts as people in New York.
0:47:23 > 0:47:26Right, do you want a free doughnut?
0:47:26 > 0:47:28Er...I would like this one.
0:47:28 > 0:47:29- The same one.- Yeah, yeah, yeah.
0:47:32 > 0:47:34So can I offer you a doughnut?
0:47:34 > 0:47:37Yeah, go for it, go for it, yes!
0:47:37 > 0:47:38I'm on a diet.
0:47:38 > 0:47:39XAND LAUGHS
0:47:41 > 0:47:42- Is that good?- Yeah, it's good.
0:47:44 > 0:47:46Everyone pick a doughnut.
0:47:47 > 0:47:50- That's my favourite one.- Is it? - It's my favourite one as well.
0:47:52 > 0:47:54You said that was your favourite one, why?
0:47:55 > 0:47:57Just cos I've tried practically all of them
0:47:57 > 0:47:59and I just like this one.
0:47:59 > 0:48:02- Guys, thank you very much. - Thank you!- Enjoy your day!
0:48:02 > 0:48:04So it's really interesting - all the glazed doughnuts have gone,
0:48:04 > 0:48:06only one person picked the chocolate one.
0:48:06 > 0:48:10Everyone seems to be going for the glazed ring.
0:48:10 > 0:48:12Let's see if that continues.
0:48:13 > 0:48:19'So why is that? What's so special about this particular doughnut?
0:48:24 > 0:48:27'The doughnut preferences of Londoners and New Yorkers
0:48:27 > 0:48:31'is in fact a clue to what we think is some of the most intriguing
0:48:31 > 0:48:32'new science in nutrition.
0:48:34 > 0:48:38'The real work is being done with rats and what they like eating.
0:48:40 > 0:48:43'Everyday rodents who work with Professor Paul Kenny,
0:48:43 > 0:48:47'a world-renowned researcher in the neurobiology of obesity
0:48:47 > 0:48:50'and, rather interestingly, addiction.
0:48:50 > 0:48:54'He devised a series of elegant experiments to work out
0:48:54 > 0:48:55'what foods we like and why.
0:48:58 > 0:49:00'The first thing he did was feed his rats sugar.
0:49:00 > 0:49:02'And they could have as much as they wanted.'
0:49:04 > 0:49:07The animals, of course, enjoy them and they'll consume vigorously,
0:49:07 > 0:49:10but they tend not to gain weight, because what they do is
0:49:10 > 0:49:13they adjust the consumption of other macronutrients to compensate.
0:49:13 > 0:49:17So, on average, animals with access to high-sugar solutions
0:49:17 > 0:49:20consumed the same amount of calories each day as they would
0:49:20 > 0:49:22if they weren't having access to those solutions.
0:49:22 > 0:49:26Really? So if you let a rat drink all the soda it wants to,
0:49:26 > 0:49:30or you let it have unlimited access to sugar, it doesn't get fat?
0:49:30 > 0:49:32Typically, no.
0:49:32 > 0:49:36'Then, he gave them as much fatty food as they wanted.'
0:49:36 > 0:49:38If you just give them access to fat,
0:49:38 > 0:49:40they will gain some weight, but really not that much,
0:49:40 > 0:49:44and what you find is they don't eat as much, physically eat as much
0:49:44 > 0:49:46food as they would've before, the reason being
0:49:46 > 0:49:48that they know that the fat is high in calories
0:49:48 > 0:49:50and their body is quick to deal with that.
0:49:50 > 0:49:54They have signals that tell them, "You've had enough, stop eating."
0:49:54 > 0:49:56'And there's something simple you can do at home to get
0:49:56 > 0:49:59'a sense of what Professor Kenny's been studying.'
0:50:02 > 0:50:05This is double cream and it's thick,
0:50:05 > 0:50:08it's luxurious, it's rich,
0:50:08 > 0:50:09it's creamy...
0:50:12 > 0:50:14..and it's really boring.
0:50:14 > 0:50:16This is sugar.
0:50:23 > 0:50:29After even with one mouthful, it's overpowering.
0:50:31 > 0:50:33BUT if we mix them together...
0:50:42 > 0:50:44Now, that stuff I could eat all day,
0:50:44 > 0:50:47and in fact, we do eat this all the time,
0:50:47 > 0:50:50cos basically, what we've just made is ice cream.
0:50:53 > 0:50:57Now, this ice cream is absolutely delicious and the reason it tastes
0:50:57 > 0:51:01so good is because the combination of fat and sugar is unbelievable.
0:51:03 > 0:51:04Mm.
0:51:07 > 0:51:10So, Professor Kenny took this simple insight
0:51:10 > 0:51:14and fed his rats foods that were high in fat and sugar.
0:51:14 > 0:51:17So what happened when you fed cheesecake to rats?
0:51:17 > 0:51:21They practically stopped eating the regular, healthy food that
0:51:21 > 0:51:24was there, but they didn't binge on the high fat, high sugar stuff,
0:51:24 > 0:51:27they grazed on it, but that was their main source of calories.
0:51:27 > 0:51:29This is the going to the fridge and just having a spoonful
0:51:29 > 0:51:31- of ice cream every 20 minutes. - Precisely, yeah.
0:51:31 > 0:51:34You know, you get up and you eat, but if you're going to eat
0:51:34 > 0:51:37it's for that type of food and you tend to eat much more frequently.
0:51:37 > 0:51:39You're not gorging on it, but that's what you eat continuously.
0:51:39 > 0:51:42And those animals gained a massive amount of weight,
0:51:42 > 0:51:45they really gained a lot of weight, and they became sedentary.
0:51:45 > 0:51:46They slept a lot, didn't move around,
0:51:46 > 0:51:48but that was where they got their calories from.
0:51:51 > 0:51:54What Professor Kenny's discovered is that,
0:51:54 > 0:51:56unlike fat and sugar on their own,
0:51:56 > 0:52:00the rats had no off switch when it came to fat and sugar combined.
0:52:00 > 0:52:04The combination of fat and sugar is completely different
0:52:04 > 0:52:07than either macronutrient alone, and it tastes remarkably good.
0:52:10 > 0:52:14And so what you have are these systems in the brain that are there
0:52:14 > 0:52:16to respond to not whether you need food to live,
0:52:16 > 0:52:19but whether you like using food,
0:52:19 > 0:52:22and they're engaged, they're called hedonic systems.
0:52:24 > 0:52:27It's much like what happens with drug addiction.
0:52:27 > 0:52:29You don't need heroin, you don't need cocaine,
0:52:29 > 0:52:32it's got no nutrient value, it's got no caloric value,
0:52:32 > 0:52:35it doesn't do anything for you except make you feel good.
0:52:38 > 0:52:41And it's exactly those hedonic systems in the brain that we think
0:52:41 > 0:52:45are being impacted far more when you consume food
0:52:45 > 0:52:49that's rich in fat and sugar, than consuming either sugar or fat alone.
0:52:52 > 0:52:55When you think about it, we all know we need to eat to live.
0:52:59 > 0:53:02But what Professor Kenny's discovered is that the combination
0:53:02 > 0:53:06of fat and sugar supercharges the brain's reward system,
0:53:06 > 0:53:10overpowering its ability to tell us to stop eating.
0:53:13 > 0:53:16And it's a manufactured combination,
0:53:16 > 0:53:18you can't find it anywhere else in nature.
0:53:25 > 0:53:27But here's what's even more remarkable.
0:53:29 > 0:53:31He's discovered that his rats didn't just like
0:53:31 > 0:53:33a mixture of fat and sugar,
0:53:33 > 0:53:38the ratio of fat to sugar was crucial to how much they liked it.
0:53:40 > 0:53:43When I looked at the composition of cheesecake and I was surprised.
0:53:43 > 0:53:47It had a highest percentage of fat of any food item
0:53:47 > 0:53:49that we looked at that wasn't actually pure fat,
0:53:49 > 0:53:52and it had remarkably high levels of sugar. So it was
0:53:52 > 0:53:55- the combination...- What's the ratio of fat and sugar in cheesecake?
0:53:55 > 0:53:57- It's pretty much 50/50.- Really?
0:53:57 > 0:53:59It's about a half fat and the rest of it sugar
0:53:59 > 0:54:02with various other things to keep the whole product together.
0:54:02 > 0:54:05- OK.- So it's basically half fat and half sugar.
0:54:05 > 0:54:06Chaps, can I offer you doughnuts?
0:54:06 > 0:54:08OK, there you go, go for it.
0:54:08 > 0:54:11- I like these ones. - Tuck in, there's no trick.
0:54:13 > 0:54:16Now remember, the most popular doughnut was this one,
0:54:16 > 0:54:18the glazed ring,
0:54:18 > 0:54:21and there's something really special about this doughnut,
0:54:21 > 0:54:25it's got an exactly 50/50 mixture of fat and sugar.
0:54:25 > 0:54:28The pink one, that's got extra sugar on the top,
0:54:29 > 0:54:32and this one is filled with cream.
0:54:33 > 0:54:34So there's no question,
0:54:34 > 0:54:38we absolutely love this combination of fat and sugar.
0:54:40 > 0:54:43It's no surprise that people liked this doughnut.
0:54:43 > 0:54:46It tends to be the bestseller on both sides of the Atlantic.
0:54:52 > 0:54:55The fact that the world is getting fatter is a new phenomenon,
0:54:55 > 0:54:57and what seems to be driving it,
0:54:57 > 0:55:00at least according to Professor Kenny, is processed food,
0:55:00 > 0:55:03because that's where you find this deadly combination
0:55:03 > 0:55:07of fat and sugar that you don't find anywhere else in nature.
0:55:07 > 0:55:11And what this does is it fundamentally interferes
0:55:11 > 0:55:14with our mechanisms of self-regulation and reward.
0:55:22 > 0:55:25It seems that it's fat and sugar together,
0:55:25 > 0:55:28not fat or sugar alone, that's the real problem.
0:55:30 > 0:55:35And Chris wanted to find out from Professor Jebb what we could do about it.
0:55:36 > 0:55:38When people tell me they crave sugar,
0:55:38 > 0:55:41I say, "What, sugar out of the sugar bowl?
0:55:41 > 0:55:44"Oh, no, no, no." Or fat, pats of butter? Generally not.
0:55:44 > 0:55:48What people really seem to desire, whether that's physiological
0:55:48 > 0:55:52or whether it's a learnt behaviour is these fat/sugar combinations.
0:55:52 > 0:55:56They are very energy dense, so they pack the calories in,
0:55:56 > 0:55:59and they are unbelievably pleasurable and attractive.
0:55:59 > 0:56:01Are these temptations for you as well?
0:56:01 > 0:56:03Oh, I think they're temptations for most of us.
0:56:03 > 0:56:05One of the things that I often say
0:56:05 > 0:56:09is it's astonishing that any of us stay slim.
0:56:09 > 0:56:12In a world like this where in Britain we are surrounded
0:56:12 > 0:56:18by pretty delicious, relatively affordable, palatable foods,
0:56:18 > 0:56:22actually you have to exert quite a level of dietary restraint
0:56:22 > 0:56:26if you're not going to effectively just sleep-walk into obesity.
0:56:26 > 0:56:28So I want your top tip,
0:56:28 > 0:56:32a basic rule, like my go to thing when I'm feeling weak.
0:56:32 > 0:56:36By making some pretty modest changes, but right across your diet.
0:56:36 > 0:56:40Certainly cutting out some of those kind of discretionary
0:56:40 > 0:56:44treat type foods which are no longer really treats,
0:56:44 > 0:56:46- they've become everyday items. - Yes.
0:56:46 > 0:56:48If you take those out you can cut calories
0:56:48 > 0:56:52and you can cut lots of those other nutrients of concern.
0:56:52 > 0:56:54So you end up with a healthier diet
0:56:54 > 0:56:57and one on which you can also lose some weight.
0:56:57 > 0:56:59And I think that really is the secret to developing
0:56:59 > 0:57:03a much more holistic attitude to food,
0:57:03 > 0:57:08which doesn't sort of believe that any one item is a saviour
0:57:08 > 0:57:12or a sinner, it is about the overall balance of the diet.
0:57:20 > 0:57:21We've all heard that before
0:57:21 > 0:57:25but the difference is that we now know our enemy.
0:57:27 > 0:57:28It's not fat.
0:57:30 > 0:57:32And it's not sugar.
0:57:33 > 0:57:35But the deadly, addictive,
0:57:35 > 0:57:39delicious mixture of fat and sugar combined.
0:57:42 > 0:57:45What's amazing to me about all this is that
0:57:45 > 0:57:47I've been a doctor for ten years,
0:57:47 > 0:57:48I've spent six years at medical school,
0:57:48 > 0:57:52and I thought I knew a lot of this stuff and I just didn't,
0:57:52 > 0:57:54like I was wrong about a lot of stuff.
0:57:54 > 0:57:56So basically what I get out of this is
0:57:56 > 0:58:00I have to avoid the processed food, the doughnuts, the ice cream,
0:58:00 > 0:58:04the cheesecake, that sort of 50/50 fat/sugar mixture
0:58:04 > 0:58:07I cannot stop eating, and it's... and that's the problem.
0:58:07 > 0:58:09So I'm going to cut those out completely.
0:58:09 > 0:58:12So that where I end up is going all faddish diets,
0:58:12 > 0:58:16all faddish diets, are wrong and misguided,
0:58:16 > 0:58:17- all of them.- Yeah.
0:58:17 > 0:58:19And doing exercise is really important.
0:58:19 > 0:58:22You need to keep the muscle because muscle is an endocrine organ
0:58:22 > 0:58:25that affects your whole metabolism.
0:58:25 > 0:58:27So, in the end, as doctors, we'd love to be able to give
0:58:27 > 0:58:30one simple rule or give you a pill that would fix all this,
0:58:30 > 0:58:32but in the end we can't.
0:58:32 > 0:58:34- It's up to you. - It's up to YOU.
0:58:34 > 0:58:37All right, it's up to... It's up to you too.