Five years ago, Dr Michael Mosley started a health revolution with The Fast Diet, telling the world about the incredible power of intermittent fasting. Since then, we've learned a whole lot more, and here Dr Mosley brings it all together to uncover the magic number of calories for health and weight loss: 800. If you are one of the millions of followers of The Fast Diet, or have seen the power of The 8-Week Blood Sugar Diet in preventing and reversing type 2 diabetes, then you will know what fasting can do for your health. In this new book, Michael updates the science - drawing on both the astonishing results of Professor Roy Taylor's pioneering DiRECT study at Newcastle University, which proves the 800 methodology, and on Michael's own pool of data and case studies. The result is an easy-to-follow new programme built around a more manageable 800-calorie Fasting Day. Working on his personal rationale that he always tries the things he recommends, Michael puts on 10% of his body weight - about 8kg - for the book. In his own `Supersize Me' experiment, he documents what the extra weight does to his blood pressure, cholesterol, blood sugar levels, hunger hormones, gut bacteria, etc, and then sees how quickly he can shed it on the 800, recording the often surprising impact on all aspects of his health.