When Dr. Michael Mosley and I started to sketch out plans for The FastDiet in October 2012, we had little idea that its impact would prove to be so great. In the months since, the book has received a hugely positive response, and interest around the world is growing daily, in Korea, Brazil, Israel, Australia, Taiwan, the United States—anywhere people are looking for a leaner, fitter life. Hundreds of people have written to us, often with great tenderness and emotion, about their weight loss and health improvements. There has been much enthusiasm from people in the public eye, too. As British food writer and cook Hugh Fearnley-Whittingstall wrote in the newspaper The Guardian, “I find myself beguiled, for the first time ever, really, by a new diet. The FastDiet, by Michael Mosley and Mimi Spencer, makes a compelling promise that with regular fasting (they propose two days out of every seven) you will quickly lose weight . . . I believe in this fasting thing, I really do . . . I’ve lost eight pounds already, and I find the whole thing rather exhilarating. I feel I might just be part of a health revolution.”
Allison Pearson, a columnist at The Daily Telegraph, described The FastDiet as her “new bible” and added, “I no longer feel the need to sleep in the afternoon. My stomach has definitely shrunk. The other night it protested when I tried to finish dinner: a world first. Scientists swear that the fasting diet will add years to your life. Me, I’m just happy to have finally shifted that stubborn baby weight. About time, too. The baby was seventeen last week.”
At thefastdiet.co.uk, the comments and questions keep rolling in. The FastDiet has always been a conversation, never a set of commandments; we are not interested in promoting diet dependency, only in investigating an idea that appears to have significant health-giving potential. So we’re fascinated by your stories, your successes, and your occasional blips, and as the science develops, we hope to have more answers to share.
In the meantime, many of you have requested inspiration for what to eat on your twice-weekly fast days. If you’ll excuse the obvious oxymoron, The FastDiet Cookbook is our answer. But before we pull on an apron and raid the fridge, it’s worth taking a brief detour into the science behind intermittent fasting, and how the FastDiet came to be.
In 2012, Dr. Michael Mosley, an overweight medically trained journalist, discovered that he was a borderline diabetic with very high levels of “bad” cholesterol. He was told by his doctor that he needed to start medication and that unless he did something about it, within ten years he would be swallowing eight pills a day, like the average sixty-year-old European or American.
Keen to find a nonpharmaceutical way to change his fate, he tracked down and interviewed scientists doing cutting-edge research into intermittent fasting. “Fasting,” in this context, does not mean avoiding all food; it simply means cutting back, for relatively short periods of time, on some foods.
In our society, we tend to eat all the time—and that constant overeating doesn’t just make us fat; it also keeps our bodies in permanent “go” mode. This leads to elevated levels of hormones like insulin and IGF-1 (insulin-like growth factor 1), which cause metabolic changes in the body. While this is a perfectly normal response to eating, the problem comes when these hormones dominate all the time; this can bring an increased risk of developing a range of diseases including diabetes, heart disease, and some cancers.
Cutting back on calories, by contrast, reduces insulin levels and gives your system a chance to rid itself of old and worn-out cells—a bit like taking your car into the garage for an occasional tune-up; doing so will almost certainly ensure that it goes on running in peak condition for longer.
Weight is, of course, easy to measure—you just need a bathroom scale. But what people sometimes forget in their obsession with losing weight is that what they really want to lose is fat.
Not all fat, however, is equally bad. Fat on the thighs and buttocks, for example, appears to be less of a health risk than excess belly fat, known as visceral fat. Visceral fat significantly increases the risk of heart disease and diabetes, which is why you should aim to have a waist (as measured around your belly button) that is less than half your height.
While losing fat, you want to preserve as much muscle as possible. One reason this is important is that muscle is metabolically active; in other words, if you take two people who are the same weight, but one is muscular and the other fat, the muscular one not only is likely to be healthier but also will burn more calories, even when sleeping. People with more muscle have a better chance of keeping weight off.
You can help preserve muscle by maintaining—or better still, increasing—the amount you exercise. This could simply mean walking more and always taking the stairs, or performing more vigorous activities such as weight training. As an added bonus, studies have shown that you are likely to burn more fat if you exercise in the fasted state rather than in the fed state.1
One of the great problems with crash diets or yo-yo dieting is that although some of the weight you lose will be fat, much of it will be muscle: On a conventional diet you will lose about 75 percent of the weight as fat and 25 percent as muscle. When you regain the weight, as most people inevitably do, the weight you regain is almost all fat.
The human trials that have been done so far suggest that intermittent fasting is unusual in that the weight loss appears to be almost all fat, and, importantly, much of the fat you lose is the dangerous type from around the gut.
A number of studies involving overweight volunteers doing ADF (alternate-day fasting)2 found that when individuals were asked to eat a quarter of their normal calories one day, then eat whatever they liked the next, they lost significant amounts of weight and saw substantial improvements in their cholesterol and blood sugars. A surprising finding was that when allowed to feast, people did not do so. They reported not feeling particularly hungry after a fast day and rarely ate more than 110 percent of their normal calories. This is borne out by anecdotal evidence, too: Many people on the FastDiet simply don’t feel ravenous the following day. Their appetite and attitudes toward food seem to change, and healthier eating seems to become part of their everyday life.
Another surprising finding was that on this form of IF, individuals lost more body fat than expected. In the most recent study of thirty-two volunteers followed for three months, the average weight loss was nearly 9 pounds, almost all fat, and they lost an average of 3 inches around the waist.
In another study, 107 women were randomly allocated either to a diet where they cut their food intake to 650 calories for two days a week and tried to stick to a healthy diet for the rest of the week, or to a diet where they consumed the same total number of calories, but spread out over the week.3
After six months, the two-day fasters had lost an average of 131/4 pounds of fat and 3 inches from their waists, compared with 103/4 pounds and 2 inches for the daily dieters. They also had much greater improvements in their cholesterol and insulin levels.
So there is evidence, from human trials, of success with different forms of intermittent fasting. After some self-experimenting, Michael settled for a form he called 5:2, which is the basis of the FastDiet.
The rules are very simple.
• You eat normally for five days a week, but for two days a week you eat one-quarter of your normal calorie intake—about 600 calories for men, 500 for women.
• You can do your fast days back to back or split them. Michael tried both ways and found he preferred to split them. He did his fast days on Mondays and Thursdays.
• He also split his 600-calorie allowance on those days into breakfast and an evening meal.
On this regimen, Michael lost 19 pounds of body fat and his blood markers improved beyond recognition. He found that once he had lost the fat, he could keep it off (normally the hard bit) by using a 6:1 method of cutting calories to a quarter of his normal intake just once a week and by always taking the stairs.
Commissioned to write about intermittent fasting for The Times (London), I soon followed Michael’s lead and in four months lost 20 pounds, returning to my “wedding weight” at the age of 45. Toward the end of 2012, inspired by the success of the 5:2 pattern, Michael and I cowrote The FastDiet. It became an instant best seller on both sides of the Atlantic. Intermittent fasting really is, as Hugh Fearnley-Whittingstall says, starting to look like a “health revolution.”
We believe that the FastDiet’s success has to do with its flexibility, its simple basic tenets, and the fact that it is backed by solid science. From a psychological point of view, its indisputable attraction is that calorie restriction is limited to only two days a week, leaving the rest of the time blissfully free of worry.
There are some people for whom intermittent fasting is not recommended; however, there is no evidence of significant side effects. Some people may experience headaches or constipation, particularly at first; these can generally be alleviated by drinking lots of calorie-free fluids and eating foods that are rich in fiber. Some find they get hungry late at night and can’t sleep well. It should help if you have a more substantial evening meal, or perhaps a glass of milk before bedtime.
In some ways, the FastDiet is simply a modern take on an ancient idea. In one form or another, fasting has been practiced for centuries by most of the great religions, and if done properly seems to be extremely safe.
There are, however, a number of myths around eating that might dissuade you from trying intermittent fasting. These include the ideas that
• You need to eat whenever you feel hungry.
• Eating every few hours will increase your metabolic rate.
• If you don’t eat every few hours, your blood sugar will fall and you will feel faint.
None of these widely held beliefs is backed by science. Certainly, fasting in any form can be tough to start with, but you should discover that short bouts of hunger are manageable and soon pass. Similarly, there is no metabolic advantage to spreading your calories over the day, nor is there any evidence that short periods without food will cause your blood sugar to plunge to seriously low levels. Most nights, you go 12 hours without eating anyway, and many people feel fine with a late breakfast.
You may want to get medical support before you start or if you have any questions. You will find a wealth of tips and supportive advice from those who have already tried it at thefastdiet.co.uk, where you can also contribute your experiences. By now, though, you’re probably feeling hungry. Time to move out of the classroom and into the kitchen.
We’re all different. When fasting, you may not wish to spend time in the kitchen, surrounded by ingredients and temptation. Some people want speed and simplicity, preferring to eat sparingly and basically—and there are plenty of ideas in this book that will be useful to people who want to eat in this way.
Others, like me, prefer to make fast day food interesting and flavorful, with fresh, low-calorie meals to bookend the day. I can’t promise the glorious depth of glossy butter sauces or the caramelized toffee you may find in other cookbooks. But I can offer wholesome, well-balanced, nutritious, engaging, pretty, fresh food that’s simple to prepare and easy to understand. I also suggest more unusual dishes to stretch the imagination and take us all on a bit of a journey.
In fact, I would even argue that the FastDiet is a “diet for foodies.” While you restrict calories—deliciously, if you wish, and with as much fanfare as you dare within the calorie budget—on two days each week, on the other five days you can eat absolutely normally. We don’t suggest bingeing, but we do advise forgetting that you are on a diet at all. Five days a week, the FastDiet is—and should be—an irrelevance.
What intermittent fasting will do, however, is encourage you to cut back on processed foods, together with their attendant preservatives and packaging. It insists that you eat fresh, good produce for two days a week. The upshot over time? We are all more engaged with the food on our plates.
On the FastDiet, you occasionally eat less, and therefore you spend less, an idea well suited to these days of austerity. One FastDiet fan named Snorvey writes of his shopping bills: “They’re certainly lower. I hadn’t even thought about it till someone mentioned it elsewhere, but at a rough guestimate, they’re about 15 percent lower. A projected amount of 395,000 calories of food not eaten per year (between two of us—the wife is following the 5:2 as well) would add up to a fair bit of money over the year.”
This book will help you develop a loose repertoire of meals that are sometimes hasty, always tasty, but above all low in fast-release carbs, which means that if you are calorie counting in the traditional way—day in, day out—this book will serve you equally well; you could happily use it as an everyday low-cal cookbook.
In fact, one of the key changes that will hopefully occur over the course of several months on the FastDiet, as many fasting fans have attested, is that your appetite will alter and you will start to crave the good things in life on any day: You may develop a yen for fresh salads, fabulous soups, lean proteins, good carbs, sparky flavor combinations, or satiating breakfasts that don’t unduly bother the frying pan. You’ll find many recipes here that meet these requirements. The book works, too, for people who are dairy- or wheat-intolerant, as very few of the recipes contain either. And it’s also pretty good for vegetarians, as lots of the recipes rely on plant proteins.
When you’re not fasting, the book still has plenty to offer. Play around with some of the ingredients, bump up the numbers, add a chunk of sourdough bread or a tumble of noodles, rice on the side or buttered corn on the cob . . . all of them will make for good eating any day of the week.