Diet Review: The Fast Diet

Featured Article, Weight Loss, Weight Loss Plans
on May 15, 2013
The Fast Diet, by Dr. Michael Mosley and Mimi Spencer reivew.

Spry editor Lisa Delaney is one of the rare souls who know what it’s like to be an “after.” This journalist and author of Secrets of a Former Fat Girl shed 70 pounds—and six dress sizes–and has kept it off for 20 years. She answers your questions here each week.

DEAR READERS: Ready for another in my series of diet book reviews? You’d better be.

The plan: The Fast Diet, by Dr. Michael Mosley and Mimi Spencer

The premise: You’re heard of juice fasts and cleanses, but The Fast Diet brings to the fore what’s called “intermittent fasting”—regular intervals of fasting interspersed with days of normal eating. Mosley’s and Spencer’s version of this is what they call the 5:2 diet—two days of eating 500-600 calories (the lower amount for women, the higher amount for men), and then eating what you want for the remaining five days.

The 5:2 concept hit the world during the summer of 2012, when Mosley, a trained doctor and BBC producer, agreed to be a guinea pig for a BBC documentary exploring the scientific research on life extension, one component of which was calorie restriction.

Now, the idea that super-low-calorie diets can extend your life has been around for years, with some intriguing research to back it up. But the very valid question of quality vs. quantity of life has kept all but the most daring anti-aging experts from promoting it as a legitimate health strategy. Mosley, who spends almost a third of the book on the science of intermittent fasting—much of which is based solely on animal and laboratory studies—says his modification preserves the benefits of calorie restriction without sacrificing the pleasures of enjoying real food like a real person. Those purported benefits include reducing the chronic inflammation that leads to cancer, heart disease, improving blood sugar control, getting a “cognitive boost,” creating a “self-repairing physiology” and—wait for it!—“swift and sustained weight loss” while “still eating the foods you would normally, most of the time.”

Key details: One attractive thing about this program is that it’s pretty simple. Mosley suggests not scheduling your fast days consecutively (but you can if you want to); and splitting up your calories on fast days into two main meals rather than spreading them out over the course of the day, as, he claims, “a longer period without food should produce better results.” On fast days, the authors suggest eating foods high in protein and foods with a low glycemic index to ward off hunger. You can also include low-fat dairy products, and lower-glycemic grains like quinoa and oatmeal, but no starchy white carbs and certainly no sugar. The plan allows you to “top up” the low cal, low-GI leafy veggies beyond quantities you’re given—which is a good thing. If you’re losing too much weight or you’ve reached your goal, you can go to the 1:6 maintenance schedule and “still reap the anti-aging benefits of occasional fasting.” On non-fasting days, hey, anything goes: apple pie with ice cream! Pancakes for breakfast! But even so, Mosley and Spencer claim that there are spillover effects—that your appetite will change, that you’ll naturally want to eat more veggies and fewer carbs, even on non-fasting days and that “you’ll start to choose healthy foods by default, not by design.” Oh, and about exercise? Mosley cites studies that say that fasting has no adverse effects on people who do high intensity exercise. Also included in the book are recipes and photos for a month of 500-calorie meal that manage to look both appetizing and ample.

Quick cautions: Where do I start? First, although Mosley makes an intriguing case for fasting as a way to improve health measures, extend lifespan and achieve a healthy weight, he consistently rests on rat studies and conjecture as proof. Although he did the diet himself—and includes other “case studies” in the form of letters from other Fast Diet fans—I simply can’t imagine this plan turning into a binge-starve-binge cycle for most people. I know that I would very likely really let loose on my non-fasting days. I’m not convinced that two days of deprivation would lead to a more general drive to eat more healthfully. Not only that—I know how punchy, reactive and downright mean and cranky I get when I don’t eat enough. So those fast days would be brutal on me and anyone I come into contact with. The authors write that “In order to be effective … any method must be rational, sustainable, flexible and feasible over the long haul.” I disagree that The Fast Diet meets that criteria.

FFG fave? Um, no. Not a chance.

Lisa Delaney is editor of Spry magazine and Ask her your question here.