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Is there such a thing as a fast diet? Dr. Michael Mosley, a physician like me, wrote a best-selling book on this subject, aptly called
The Fast Diet: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting, which answers that question.

As a journalist for BBC in the UK, Dr. Mosley has really helped popularize one of the most powerful medical interventions I’ve ever encountered for helping people normalize their weight, namely intermittent fasting.

I’ve previously featured some of his TV documentaries on intermittent fasting and high intensity exercise in this newsletter. In those programs, Dr. Mosley reveals his own health journey, showing how he went from being overweight, diagnosed with diabetes and high cholesterol, to regaining his health.

“My doctor wanted to start me on drugs. But I said, ‘I want to see if there’s something better and alternative out there,'” he says. “I started exploring, and came across intermittent fasting…

I ended up testing all sorts of different forms of fasting, including alternate-day fasting. Eventually, I came up with something that I called the 5:2 Diet, which is really counting calories two days a week and eating normally the other five days.

I stuck to that for about three months. During that period, I lost about 20 pounds of fat, my body fat went down from 28 percent to 20 percent, and my blood glucose went back to normal.

That was two years ago and it stayed completely normal since… I have to say it’s been absolutely life-changing.”

Different Types of Fasting Regimens

Intermittent fasting is an umbrella term that covers an array of different fasting schedules. As a general rule however, intermittent fasting involves cutting calories in whole or in part, either a couple of days a week, every other day, or even daily, as in the case of the scheduled eating regimen I use myself.

In his explorations, Dr. Mosley tried a number of these different approaches, including a five-day fast, alternate day fasting (promoted by Dr. Krista Varady), and the 5:2 fast.

The five-day fast was very effective in that he lost weight and improved some of his biomarkers. But it was quite difficult to go a full five days without nearly any food whatsoever. The alternate day fasting also worked, but he found it to be a bit inconvenient.

“And then I came across some work done in England by Dr. Michelle Harvie, which was [fasting] two days a week. I thought, ‘I can handle two days a week.’ In a way, I kind of combined a number of different techniques together and ended up with the 5:2 plan.

One of my inspirations was the Prophet Muhammad because he had told his followers they all need to fast on a monthly basis for Ramadan but also cut your calories two days a week – Mondays and Thursdays. That’s what I did.

I’m not a very religious person, but I do believe that great religions have a lot to teach us, whether it is mindful meditation or indeed some of the benefits of fasting. I think the reason that these ideas persist is there is something very profound about them.”

On the 5:2 plan, you cut your food down to one-fourth of your normal daily calories on fasting days (about 600 calories for men and about 500 for women), along with plenty of water and tea. On the other five days of the week, you can eat normally.