USDA chart

The 5:2 Diet Doesn't Add Up

by Susan Lesch. April 1, 2016

a frosted chocolate cupcake
175 calories (Photo: Wikimedia Commons)

Dr. Michael Mosley and Mimi Spencer promise the world with their FastDiet, known as the 5:2 diet. Unfortunately the numbers just aren't there to support it. I find their invitation to eat anything and their diet to be a poor recipe for weight loss!

The admonition to eat anything you want five days a week is seductive. I had visions of a daily treat, say, a cupcake. But when it comes down to it, nobody gets to eat whatever they want. Here's why.

On the 5:2 diet, the goal is to lose one pound a week. Men eat 600 calories and women eat 500 calories per day on two non-consecutive days, and then for five days everyone can eat whatever they want. Here I use a general guide for people of low activity, found on the USDA website. And I'll use the familiar 3,500 calories per pound of weight change.

Figure it out for yourself. Say you are a male between 31 and 50 years of age. Normally you need 2,200 calories per day including 265 empty calories. On the 5:2 diet you eat 600, saving 1,600 calories a day for two days. That means you can eat a grand total of 2,140, including 265 empty calories per day for five days.

It's worse for me. I'm a female and over 51. Normally I get 1,600 calories including 120 empty calories per day. On the 5:2 diet, I get 500 calories, saving 1,100 calories per day for two days. Then I get 1,340 calories per day including 120 empty calories for five days.

If I choose to exercise more to increase the number of available calories, there would be no reason to diet.

Sources of solid fats and added sugars (empty calories) include cakes, cookies, pastries, donuts, sodas, energy drinks, sports drinks, fruit drinks, cheese, pizza, ice cream, sausages, hot dogs, bacon, and ribs. On the 5:2 diet I can eat no more than my normal 120 calories of empty calories so I have room for enough nutrients to remain healthy. Say goodbye to that cupcake!

Empty Calories. United States Department of Agriculture. ( Retrieved from on March 30, 2016.