The Fast Diet has become a remarkable phenomenon since it was first published in 2013, with more than a million books sold worldwide and translations into 32 languages. Here, co-author Mimi Spencer explains the idea and its appeal.

In the 18 months since I wrote The Fast Diet with Dr Michael Mosley, people have often asked me why it has touched such a nerve. Why have people embraced it so enthusiastically? My answer is always the same.

Because it works. Because it's simple. Because you can do it.

How it works

Those might sound like the overly optimistic words of a preacher. But the diet (it's more of a lifestyle really, but we'll get to that) really is simplicity itself. The Fast Diet is also called the 5:2 diet, because of its single key premise: for two days a week, you slash your calories to a quarter of the usual intake (so, that's 500 for a woman, 600 for a man). On the other five days, you are blissfully free of calorie counting - which makes the Fast Diet, unlike conventional every-day dieting, so sustainable. If you follow this easy proposition - really, you could write it on the back of your hand - you can not only expect to lose weight; the metabolic changes which take place during short-term, intermittent fasting mean that you should also cut your risk of a range of age-related diseases, including diabetes, Alzheimer's and some types of cancer. Believe it or not, it can even boost your brain. This is what takes the Fast Diet way beyond fad and into forever.

What's important is that you are not depriving yourself of treats every day. You can still enjoy good food, good wine (it has been called a 'diet for foodies'), you still keep your social life all but unaltered. Most of the time, you don't diet at all. This, I think, is the psychological key to its success and long-term sustainability.

What happens on a Fast Day?

On a Fast Day, of course, you may need to rise to the challenge of an occasional hunger pang. It's worth knowing that hunger is not constant, but it comes in waves - and we recommend that you have as long a 'fasting window' as possible on a Fast Day, so you'll probably feel a bit peckish at some point. The most widely practiced Fast Diet method involves eating breakfast (perhaps eggs or porridge or fish), then 8-12 food-free hours, then a light supper of protein and vegetables in the evening.

Yes, it can be a challenge. But it can also be a liberation from the constant grazing which characterises the way so many of us live. I often hear from people who have been fearful of hunger. But once they experience it (for the short period advised on the Fast Diet), it can in fact be an enjoyable experience. Honestly.

Kickstart the Fast Diet at Constance Le Prince Maurice, Mauritius

Of course, embarking on any new programme requires willpower and a helping hand. That's why I've worked with Constance Hotels & Resorts at Le Prince Maurice in Mauritius to develop the Kickstart the Fast Diet programme. Here, guests can embark on the Fast Diet with the assistance and support of a world-class hotel and its excellent staff.

Executive Chef Michael Scioli has introduced Fast Diet choices to his menus.  Each dish, whether it's fresh sashimi, grilled fish from the lagoon or a spiced Mauritian classic, is handpicked to suit a Fast Day, or designed to encourage healthy eating on a Non-Fast Day. Each menu capitalises on fresh local produce so well-suited to the glorious Mauritian climate. Guests can also experience spa treatments - shiatsu, lymphatic massage, wraps, reflexology - with the aim of complementing the fasting process. At Le Prince Maurice, a personal trainer is also on hand to offer advice for combining fasting and exercise, while yoga on the beach with renowned teacher Isabelle Lamant is an ideal way to bookend the day. You can even have a Fast Diet cooking lesson on the pool deck with the Indian Ocean as your backdrop.

I have just spent a week in Mauritius fine-tuning the Kickstart programme and I'm absolutely delighted with the result. After all, there are few more beautiful and relaxing places on earth to embark on the Fast Diet. Come and see. And don't forget to pack your bikini!

Find out more about the Fast Diet

The Fast Diet by Mimi Spencer and Dr Michael Mosley

The Fast Diet Recipe Book by Mimi Spencer with Dr Sarah Schenker

and Fast Exercise by Dr Michael Mosley are all published by Short Books and available on www.amazon.co.uk

Mimi's new book, Fast Cook, comes out on March 6th 2014.

For more in-depth information about the Fast Diet, go to Michael and Mimi's website, www.thefastdiet.co.uk

Kickstart the Fast Diet is available at the Constance Prince Maurice Hotel.