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August 20, 2012 7:24 AM
Hi everyone
I wondered if anyone watched Michael Mosley on the UK Horizon programme called "Eat, Fast and Live Longer"?

The link:

The power of intermittent fasting

Michael Mosley fasted for two days every week
Scientists are uncovering evidence that short periods of fasting, if properly controlled, could achieve a number of health benefits, as well as potentially helping the overweight, as Michael Mosley discovered.

I'd always thought of fasting as something unpleasant, with no obvious long term benefits. So when I was asked to make a documentary that would involve me going without food, I was not keen as I was sure I would not enjoy it.

But the Horizon editor assured me there was great new science and that I might see some dramatic improvements to my body. So, of course, I said, "yes".

I am not strong-willed enough to diet over the long term, but I am extremely interested in the reasons why eating less might lead to increased life span, particularly as scientists think it may be possible to get the benefits without the pain.

Michael Mosley presents Horizon: Eat, Fast and Live Longer on BBC Two at 21:00 BST on Monday 6 August
Watch online afterwards via iPlayer (UK only) or browse Horizon clips at the above link
How you age is powerfully shaped by your genes. But there's not much you can do about that.

Calorie restriction, eating well but not much, is one of the few things that has been shown to extend life expectancy, at least in animals. We've known since the 1930s that mice put on a low-calorie, nutrient-rich diet live far longer. There is mounting evidence that the same is true in monkeys.

Growth hormone

The world record for extending life expectancy in a mammal is held by a new type of mouse which can expect to live an extra 40%, equivalent to a human living to 120 or even longer.

It has been genetically engineered so its body produces very low levels of a growth hormone called IGF-1, high levels of which seem to lead to accelerated ageing and age-related diseases, while low levels are protective.

Professor Longo has investigated growth hormone deficiency in humans A similar, but natural, genetic mutation has been found in humans with Laron syndrome, a rare condition that affects fewer than 350 people worldwide. The very low levels of IGF-1 their bodies produce means they are short, but this also seems to protect them against cancer and diabetes, two common age-related diseases.

The IGF-1 hormone (insulin-like growth factor) is one of the drivers which keep our bodies in go-go mode, with cells driven to reproduce. This is fine when you are growing, but not so good later in life.

There is now evidence suggesting that IGF-1 levels can be lowered by what you eat. Studies on calorie restrictors suggest that eating less helps, but it is not enough

As well as cutting calories you have to cut your protein intake. Not entirely - that would be a very bad idea. It's about sticking to recommended guidelines, something most of us fail to do.

The reason seems to be that when our bodies no longer have access to food they switch from "growth mode" to "repair mode".

As levels of the IGF-1 hormone drop, a number of repair genes appear to get switched on according to ongoing research by Professor Valter Longo of the University of Southern California.

Intermittent fasting
One area of current research into diet is Alternate Day fasting (ADF), involving eating what you want one day, then a very restricted diet (fewer than 600 calories) the next, and most surprisingly, it does not seem to matter that much what you eat on non-fast days.

Dr Krista Varady of the University of Illinois at Chicago carried out an eight-week trial comparing two groups of overweight patients on ADF.

"If you were sticking to your fast days, then in terms of cardiovascular disease risk, it didn't seem to matter if you were eating a high-fat or low-fat diet on your feed (non-fast) days," she said.

I decided I couldn't manage ADF, it was just too impractical. Instead I did an easier version, the so-called 5:2 diet. As the name implies you eat normally 5 days a week, then two days a week you eat 500 calories if you are a woman, or 600 calories, if you are a man.

There are no firm rules because so far there have been few proper human trials. I found that I could get through my fast days best if I had a light breakfast (scrambled eggs, thin slice of ham, lots of black tea, adding up to about 300 calories), lots of water and herbal tea during the day, then a light dinner (grilled fish with lots of vegetables) at night.

"On my feed days I ate what I normally do and felt no need to gorge"

I stuck to this diet for 5 weeks, during which time I lost nearly a stone and my blood markers, like IGF-1, glucose and cholesterol, improved. If I can sustain that, it will greatly reduce my risk of contracting age-related diseases like cancer and diabetes.

Current medical opinion is that the benefits of fasting are unproven and until there are more human studies it's better to eat at least 2000 calories a day. If you really want to fast then you should do it in a proper clinic or under medical supervision, because there are many people, such as pregnant women or diabetics on medication, for whom it could be dangerous.

I was closely monitored throughout and found the 5:2 surprisingly easy. I will almost certainly continue doing it, albeit less often. Fasting, like eating, is best done in moderation.

Michael Mosley presents Horizon: Eat, Fast and Live Longer on BBC Two at 21:00 BST on Monday 6 August. Watch online afterwards via iPlayer (UK only) or browse Horizon clips at the above link.
August 20, 2012 7:27 AM
yes i saw it too - I'm definitely going to try it - I don't think 600 cals 2 days out of 7 would be so hard. It's confusing though - I've been a fan of the group Eat More to Weigh Less and the general 'mantra' that one should never eat less than BMR calories (1800 for me) - so this evidence kind of flies in the face of all that. Personally I'll go with the scientific evidence over the conjecture.
August 20, 2012 8:13 AM
By Dr Michael Mosley
4:29PM BST 16 Aug 2012

A couple of months ago I set myself an ambitious goal: to find a way to live longer, stay younger and lose weight. I also wanted to go on enjoying the foods I normally eat and make as few changes to my lifestyle as possible. After talking to several scientific experts, I have spent the past few months trying a controversial diet that challenges conventional views about how and when we should eat. It is called intermittent fasting – reducing your food intake on alternate days.

Although most of the great religions advocate fasting (devout Muslims finish fasting for Ramadan this weekend), I have always been sceptical about the medical benefits and followed the standard advice, namely “never skip a meal and never crash-diet”.

The reasoning behind this is that people who skip meals tend to eat high-fat snacks when they get hungry, while those who crash-diet lose weight fast but what they lose is mainly water, with some fat and muscle thrown in. When crash-dieters give up, as invariably they do, they pile on the pounds, mainly as fat. It is known as yo-yo dieting and does you no good.

So before doing anything that involved fasting, I wanted to find out a lot more about what I was getting myself into.

I started at the London Marathon. At this year’s event there were more than 7,000 runners aged over 50, and seven who were over 80. The most impressive competitor, however, had to be Fauja Singh, also known as “the turbaned tornado”. At 101, he is the world’s oldest marathon-runner.

Fauja is a bit of a mystery. His lifestyle is nothing like that of the average marathon-runner. He is a strict vegetarian, so he is not getting muscle-building protein from fish or meat. He also eats much the same thing every day — he lives mainly on lentils, vegetables garnished with ginger, brown bread, fruit and yogurt — and his portions are tiny (no carb-loading for Fauja). Which explains his weight. He is 5ft 8in tall and weighs just 53kg — about 8 stone.

He attributes his success to his eating habits: “My life is protected because I control my eating.”

Fauja is right to believe that controlled eating is the way to a longer and healthier life. Scientists have known since the Thirties that one of the best ways to extend life is to eat a nutritionally rich but calorie-restricted diet. Mice on such a diet live up to 40 per cent longer than normal mice.

The trouble is, I cannot seriously imagine living on a severely calorie-restricted diet for the rest of my life. Fortunately, there is an alternative that seems to offer many of the same benefits — intermittent fasting.

One scientist who has been studying fasting for many years is Professor Valter Longo, the director of the University of Southern California’s Longevity Institute. When I visited him for BBC Two’s Horizon, he showed me a remarkable little mouse that had been genetically engineered to live longer.

“This,” he proudly told me, “is a dwarf or Laron mouse. These mice hold the record for longevity extension in a mammal.” The average mouse has a lifespan of about two years. Laron mice can live for up to five years.

The mouse I held was the equivalent of an 80-year-old human being. Like his genetically engineered relatives, he should live to the equivalent of 120, maybe even 180.

Laron mice are largely immune to heart disease and cancer, and when they die it is usually of natural causes. Oddly enough, when the mice are examined, scientists are often unable to find a cause of death. The heart just stops.

One of the links between fasting and longevity seems to be a hormone called insulin-like growth factor 1 (IGF-1). As Prof Longo explained, IGF-1 and other growth factors keep our cells constantly active. It’s like driving along with your foot hard on the accelerator pedal.

You need adequate levels of IGF-1 and other growth factors when you are growing, but high levels later in life appear to lead to accelerated ageing. The evidence for this comes not just from animals such as the Laron mice, genetically engineered so that they don’t respond to IGF-1, but also from humans.

Prof Longo has studied certain villagers in Ecuador who have a genetic defect called Laron syndrome. It is incredibly rare: fewer than 350 people worldwide are known to have the condition. Like the mice, people with Laron syndrome don’t respond to IGF-1. They are short, typically less than 4ft tall, with prominent foreheads and underdeveloped jaws.

Most surprisingly, as Prof Longo explained, they appear immune to cancer: “There are no reports, not a single one, of them ever dying of cancer, yet their relatives in the same household, the same age, get cancer like everybody else.”

They are long-lived but, unlike the mice, not exceptionally so. Prof Longo thinks this may be because they have learnt that they are naturally resistant to cancer and diabetes, and tend not to be terribly careful about their diets.

“They smoke, eat a high-calorie diet, then they look at me and say, 'Oh, it doesn’t matter, I’m immune.’ I think they would rather take the 85-year life and do what they want than the 100-year life and have to be restricted.”

Fasting lowers levels of IGF-1 and also appears to switch on a number of DNA repair genes. The reason seems to be that when we run out of food our bodies change from “growth” to “repair” mode. But Prof Longo warned me that fasting is not for the faint-hearted, and is safest done in a specialised centre or under supervision.

“There’s going to be a drop in blood pressure, a drop in glucose levels and metabolic reprogramming,” he said. “Some people faint. It’s not common but it happens.”

I started my fast on a Monday evening, after a final slap-up dinner of steak, and finished it after more blood tests on the Friday. During that time I drank black tea, black coffee and lots of water but consumed no food.

Before I did it I was convinced that hunger would build day by day, getting steadily worse until finally I gave in and raided a local bakery. But what I found was that, after the first 24 hours, things got better. I had hunger pangs, but they passed.

On the Friday morning, I had myself tested again and discovered that I had lost just over 2lb of body fat, my blood glucose levels had fallen dramatically and my IGF-1 levels, which had been towards the top end of the range, had halved.

So I had improved my body chemistry and learnt that I could tolerate hunger better than I imagined. Prof Longo warned me, however, that to maintain these benefits I would have to change what I ate.

According to Prof Longo, like many of us on a Western diet, I eat too much protein, and that helps to keep my IGF-1 levels high. Foods such as meat and fish are rich in protein, but so is milk. A skinny latte, which I drink most mornings, comes in at around 12g of protein. Recommended levels are a relatively measly 55g of protein a day.

Now this is clearly bad news for anyone on a high-protein diet such as the Atkins or the Dukan. But it is also tough for someone like me who enjoys their meat. Prof Longo is pretty much a vegan. I was prepared to give up lattes but not to go that far.

I met my next scientist, Dr Krista Varady of the University of Illinois at Chicago, in an old-fashioned American diner. We ate burgers and fries while she told me about a diet that she has been testing on human volunteers. It’s called Alternate Day Fasting (ADF) and is very simple. One day you eat whatever you want. The next day, you fast.

Fasting ADF-style isn’t as drastic as the fasting I’d tried with Prof Longo. On Dr Varady’s fasting days you are allowed about 600 calories a day if you are a man, 500 if you are a woman. The real surprise was that on my “feed days” I could eat exactly what I wanted.

Dr Varady has finished a trial, to be published next month, in which she took two groups of volunteers doing ADF for 10 weeks. One group were put on a low-fat diet on their feed days, while the other were encouraged to eat lasagnes, pizza — a typical American high-fat diet. As Dr Varady explained, the results were unexpected.

“When they signed up for the study, the people randomised into the high-fat group weren’t happy because they assumed that they wouldn’t lose as much weight as those randomised to the low-fat diet. But they did. People on the high-fat diet were losing as much and sometimes more weight, week after week.”

And it wasn’t just weight loss: the groups saw similar falls in LDL cholesterol — “bad cholesterol” — and blood pressure. Dr Varady is running a year-long trial to assess the longer-term effects of ADF on weight loss and health. She is keen to see how much her volunteers lose and how many will still be on the diet after a year.

I thought long and hard about doing ADF, but decided in the end that it sounded a little too much like hard work and would play havoc with my social life. Instead I opted for a less dramatic variant: the 5:2 diet. With this regimen you eat what you want five days a week, then twice a week you restrict yourself to just 600 calories. There have been few human trials of the 5:2 diet, so no one is certain whether it is better to eat those 600 calories in one meal or to spread them out through the day. I decided to try different approaches, to see what would work for me.

I tried skipping breakfast and lunch, then eating my 600 calories in one go at supper time. The trouble is, I hate starting the day hungry. So then I tried a large breakfast and nothing else. I got really irritable in the evenings. Finally, I went for a split: 300 calories for breakfast and 300 for supper. A typical breakfast now means two scrambled eggs and a slice of ham (quite a lot of protein, but well within limits), with plenty of water, green tea and black coffee to see me through a working day. Then, in the evening, I tuck into something like grilled fish and lots of vegetables. It is impressive how few calories there are in vegetables, and when you are hungry they are unexpectedly delicious.

There is no official guide to what a 600-calorie meal looks like — Dr Varady gives her volunteers specially prepared low-calorie meals — so I made mine up by trawling internet websites.

It doesn’t seem to matter which days of the week you do it; I prefer to do my intermittent fasts on Tuesdays and Thursdays — something, apparently, that the Prophet Mohammed recommended.

I have kept this up for two months and, after a settling-in period, it has become quite easy. It is reassuring, when you are on a restricted-calorie day, to know that the next day you can eat whatever you want. The surprising thing is that you don’t. Dr Varady said that her team expected people to gorge on their feed days, but most people are happy to eat their normal diet. Such is the power of habit.

Six weeks after starting the 5:2 diet, I had another full medical. The results were impressive. I had lost well over a stone, down to less than 12st. My blood glucose, which had been borderline diabetic, was normal and my cholesterol levels, previously high enough to necessitate medication, were also down in the healthy range. I have swapped lattes for espressos and generally cut back on protein, so my IGF-1 stayed low. I look better and I feel good on it. I still sometimes eat burgers, biscuits and cakes, but on my fasting days I eat healthily.

Intermittent fasting is not something that you will find many doctors recommending because, while there is plenty of animal data, so far there is limited evidence of its efficacy in long-term human trials. It will not suit everyone, nor is it safe for everyone. It worked for me and I will keep doing it. Or I think I will. We shall see.

For Xanthe Clay's recipes ideal for anyone on the 5:2 diet, see 5:2 diet: healthy recipes 250 calories or less

• Michael Mosley is a medical doctor, journalist and television presenter. To watch his BBC Two Horizon programme on intermittent fasting, go to the BBC iPlayer ( or visit

The 5:2 diet: what is it and how does it work?

By Jennifer Smith

• With the 5:2 diet, you can eat whatever you like five days a week — so-called feeding days. On the two “fasting days” you eat 500 calories if you are a woman, or 600 calories if you are a man.

• It doesn’t matter which days are spent “feeding” and which “fasting”, as long as the fasting days are non-consecutive and you stick to the 5:2 ratio.

• On fasting days you can consume your calories in one go, or spread them through the day — there is no medical research into whether filling up at breakfast or snacking throughout the day is more effective for weight loss.

• A typical fasting-day breakfast of 300 calories might consist of two scrambled eggs with ham (good sources of protein), plenty of water, green tea or black coffee. For a typical 300-calorie lunch or dinner, try grilled fish or meat with vegetables.

• On feeding days you can eat whatever you like. Most dieters, rather than feeling a need to gorge, found that they were happy to consume around 2,000 calories — the recommended daily intake for women (2,600 for men) — and did not crave high-fat foods.

• Contrary to popular opinion, fasting can be a healthy way to lose weight. It can reduce levels of IGF-1 (insulin-like growth factor 1, which leads to accelerated ageing), switches on DNA repair genes and reduces blood pressure, cholesterol and glucose levels.

• According to current medical opinion, the benefits of fasting are unproven. As a diet, it is not recommended for pregnant women or diabetics on medication. Anyone considering a diet that involves fasting is advised to consult their GP first, and to do it under medical supervision.
September 16, 2012 10:03 AM
I have been doing the fasting for 5 weeks now. I feel good yet I am ready to stop and return to a more [ normal to me ] :) eating schedule. I was wondering if you had done the fasting and if you had been able to monitor your progress? Thanks!
October 28, 2012 5:25 AM
I am very interested in this diet. I am not overweight, currently my bmi is 21 and I want to lose about 10lbs. I was just wondering whether this diet works if you have a normal bmi? I have tried controlling calories loads in the past but lose all motivation after a day or 2 because I love food too much. I think id be able to stick to this diet though. Hope someone can advise! x

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