The Fast Diet and me – an introduction

Fast two days a week to change your shape – and your life, says Dr Michael Mosley, co-author of The Fast Diet

Over the past few decades, food fads have come and gone, but the standard medical advice on what constitutes a healthy lifestyle has stayed much the same: eat low-fat foods, exercise more… and never, ever skip meals. Over that same period, levels of obesity worldwide have soared.


So is there a different, evidence-based approach? One that relies on science, not opinion? Well, I think there is. Intermittent Fasting.

When I first read about the alleged benefits of Intermittent Fasting, I, like many, was sceptical. Fasting seemed drastic, difficult – and I knew that dieting, of any description, is generally doomed to fail. But now that I’ve looked at it in depth and tried it myself, I am convinced of its remarkable potential.

As one of the medical experts interviewed for the Fast Diet book puts it: “There is nothing else you can do to your body that is as powerful as fasting.”

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. We 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 that it is the only intervention that has been shown to extend lifespan, at least in animals. 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 US, meeting leading scientists who generously shared their research and ideas with me. It became clear that IF was no fad.

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 (ie 600 calories).

The programme, Eat, Fast, Live Longer, which detailed my adventures with what we were now calling the 5:2 diet, went out on the BBC during the London Olympics [with an accompanying feature in Radio Times]. I expected it to be lost in the media frenzy that surrounded the Games, but instead it generated a frenzy of its own. The newspapers took up the story. Articles appeared in The Times, 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 Delhi.

People began to stop me on the street and tell me how well they were doing on the 5:2 diet. They also emailed details of their experiences. Among those emails, a surprisingly large number were from doctors. Like me, they had initially been sceptical, 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 scrutinise. They wanted me to write a book. Which is how what you are reading came about…

The promise

The Fast Diet demands we think not just about what we eat, but when we eat it

There are no complicated rules to follow; the strategy is flexible, comprehensible and user-friendly

There is no daily slog of calorie control – none of the boredom, frustration or serial deprivation that characterise conventional diet plans

Yes, it involves fasting, but not as you know it; you won’t “starve” on any given day

You will still enjoy the foods you love. Most of the time

Once the weight is off, sticking to the basic programme will mean that it stays off

Weight loss is only one benefit of the Fast Diet. The real dividend is the potential long-term health gains, cutting your risk of a range of diseases, including diabetes, heart disease and cancer

You will come to understand that it’s not just a diet. It’s much more than that: it’s a sustainable strategy for a healthy, long life

Want to know more about how to fast?

Find out more about the benefits of The Fast Diet, and the science behind it.

See seven fasting day menu examples.


Buy your copy of the Fast Diet now.