The Power of Intermittent Fasting (Updated)
THE POWER OF INTERMITTENT FASTING
• Fasting For Three Days Can Regenerate Entire Immune System
The Power of Intermittent Fasting (Updated)Apr 12
Dr. Michael Mosley
THE POWER OF INTERMITTENT FASTING
By Dr. Michael Mosley
August 4, 2012
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.
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.
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.
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.
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.
But it turns out IGF-1 levels can be lowered by fasting. 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.
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.
There is nothing else you can do to your body that is as powerful as fasting.
When we first read about the alleged benefits of intermittent fasting, we, like many, were skeptical. Fasting seemed drastic, difficult — and we both knew that dieting of any description is generally doomed to fail. But now that we’ve looked at it in depth and tried it ourselves, we are convinced of its remarkable potential. As one of the medical experts interviewed for this book puts it: “There is nothing else you can do to your body that is as powerful as fasting.”
Fasting: An Ancient Idea, a Modern Method
Fasting is nothing new. As we’ll discover in the next chapter, your body is designed to fast. We evolved at a time when food was scarce; we are the product of millennia of feast or famine. The reason we respond so well to intermittent fasting may be because it mimics, far more accurately than three meals a day, the environment in which modern humans were shaped.
Fasting, of course, remains an article of faith for many. The fasts of Lent, Yom Kippur, and Ramadan are just some of the better-known examples. Greek Orthodox Christians are encouraged to fast for 180 days of the year (according to Saint Nikolai of Zicha, “Gluttony makes a man gloomy and fearful, but fasting makes him joyful and courageous”), while Buddhist monks fast on the new moon and full moon of each lunar month.
Many more of us, however, seem to be eating most of the time. We’re rarely ever hungry. But we are dissatisfied. With our weight, our bodies, our health.
Intermittent fasting can put us back in touch with our human selves. It is a route not only to weight loss, but also to long-term health and well-being. Scientists are only just beginning to discover and prove how powerful a tool it can be.
This book is a product of those scientists’ cutting-edge investigations and their impact on our current thinking about weight loss, disease resistance, and longevity. But it is also the result of our personal experiences.
Both are relevant here — the lab and the lifestyle — so we investigate intermittent fasting from two complementary perspectives. First, Michael, who used his body and medical training to test its potential, explains the scientific foundations of intermittent fasting (IF) and the 5:2 diet — something he brought to the world’s attention during the summer of 2012.
Then Mimi offers a practical guide on how to do it safely, effectively, and in a sustainable way, a way that will fit easily into your normal everyday life. She looks in detail at how fasting feels, what you can expect from day to day, what to eat, and when to eat, and provides a host of tips and strategies to help you gain the greatest benefit from the diet’s simple precepts.
As you’ll see below, the FastDiet has changed both of our lives. We hope it will do the same for you.
Michael’s Motivation: A Male Perspective
I am a 55-year-old male, and before I embarked on my exploration of intermittent fasting, I was mildly overweight: at five feet, eleven inches, I weighed around 187 pounds and had a body mass index of 26, which put me into the overweight category. Until my midthirties, I had been slim, but like many people I then gradually put on weight, around one pound a year. This doesn’t sound like much, but over a couple of decades it pushed me up and up. Slowly I realized that I was starting to resemble my father, a man who struggled with weight all his life and died in his early seventies of complications associated with diabetes. At his funeral many of his friends commented on how like him I had become.
While making a documentary for the BBC, I was fortunate enough to have an MRI (magnetic resonance imaging) scan done. This revealed that I am a TOFI — thin on the outside, fat inside. This visceral fat is the most dangerous sort of fat, because it wraps itself around your internal organs and puts you at risk for heart disease and diabetes. I later had blood tests that showed I was heading toward diabetes, and had a cholesterol score that was also way too high. Obviously, I was going to have to do something about this. I tried following standard advice, except it made little difference. My weight and blood profile remained stuck in the “danger ahead” zone.
I had never tried dieting before because I’d never found a diet that I thought would work. I’d watched my father try every form of diet, from Scarsdale through Atkins, from the Cambridge Diet to the Drinking Man’s Diet. He’d lost weight on each one of them, and then within a few months put it all back on, and more.
Then, at the beginning of 2012, I was approached by Aidan Laverty, editor of the BBC science series Horizon, who asked if I would like to put myself forward as a guinea pig to explore the science behind life extension. I wasn’t sure what we would find, but along with producer Kate Dart and researcher Roshan Samarasinghe, we quickly focused on calorie restriction and fasting as a fruitful area to explore.
Calorie restriction (CR) is pretty brutal; it involves eating an awful lot less than a normal person would expect to eat, and doing so every day of your (hopefully) long life. The reason people put themselves through this is because it is the only intervention that has been shown to extend lifespan, at least in animals. There are at least 10,000 CRONies (Calorie Restriction with Optimum Nutrition) worldwide, and I have met quite a number of them. Despite their generally fabulous biochemical profile, I have never been seriously tempted to join their skinny ranks. I simply don’t have the willpower or desire to live permanently on an extreme low-calorie diet.
So I was delighted to discover intermittent fasting (IF), which involves eating fewer calories, but only some of the time. If the science was right, it offered the benefits of CR but without the pain.
I set off around the United States, meeting leading scientists who generously shared their research and ideas with me. It became clear that IF was no fad. But it wouldn’t be as easy as I’d originally hoped. As you’ll see later in the book, there are many different forms of intermittent fasting. Some involve eating nothing for twenty-four hours or longer. Others involve eating a single, low-calorie meal once a day, every other day. I tried both but couldn’t imagine doing either on a regular basis. I found it was simply too hard.
Instead I decided to create and test my own modified version. Five days a week, I would eat normally; on the remaining two I would eat a quarter of my usual calorie intake (that is, 600 calories).
I split the 600 calories in two — around 250 calories for breakfast and 350 calories for supper — effectively fasting for around twelve hours at a stretch. I also decided to split my fasting days: I would fast on Mondays and Thursdays. I became my own experiment.
The program, Eat, Fast, Live Longer, which detailed my adventures with what we were now calling the 5:2 diet, appeared on the BBC during the London Olympics in August 2012. I expected it to be lost in the media frenzy that surrounded the Games, but instead it generated a frenzy of its own. The program was watched by more than 2.5 million people — a huge audience for Horizon — and hundreds of thousands more on YouTube. My Twitter account went into overdrive, my followers tripled; everyone wanted to try my version of intermittent fasting, and they were all asking me what they should do.
The newspapers took up the story. Articles appeared in The Times (London), the Daily Telegraph, the Daily Mail, and the Mail on Sunday. Before long, it was picked up by newspapers all over the world — in New York, Los Angeles, Paris, Madrid, Montreal, Islamabad, and New Delhi. Online groups were created, menus and experiences swapped, chat rooms started buzzing about fasting. People began to stop me on the street and tell me how well they were doing on the 5:2 diet. They also e-mailed details of their experiences. Among those e-mails, a surprisingly large number were from doctors. Like me, they had initially been skeptical, but they had tried it for themselves, found that it worked, and had begun suggesting it to their patients. They wanted information, menus, details of the scientific research to scrutinize. They wanted me to write a book. I hedged, procrastinated, then finally found a collaborator, Mimi Spencer, whom I liked and trusted and who has an in-depth knowledge of food. Which is how what you are reading came about…
• Fasting For Three Days Can Regenerate Entire Immune System
• Documentary: ‘Eat, Fast & Live Longer’
• Fast Diet (book) by Dr Michael Moseley, Mimi Spence
• Two Horizon: Eat, Fast & Live Longer
• The Power of Intermittent Fasting