This morning, I’ve started the 5:2 diet, where each week you eat a calorie-constrained amount on 2 non-sequential days and whatever you’d like on the other five days. Men are supposed to limit the ‘fast’ days to 600 calories, women to 500. There are numerous write-ups of the dietary details and benefits (like this, and this).

5:2 is one of the many intermittent fasting diets becoming popular, like the ‘every other day’ diet (see James Hamblin, The New Way to Love Food). Intermittent fasting works on a simple principle, based on research that shows if people are given 25% of their normal calorie intake on one day, on the next they eat only slightly more — around 115% — if restrictions are relaxed on a subsequent day. So at the end of a week with 2 fasting and 5 normal days, the math is this for a diet of 2000 calories per day:

(2*25%*2000 calories)+(5*115%*2000 calories) = 12,500 calories

versus the 14,000 that would come from seven days of 2000 calories, each day.

Research, both scientific and informal, seems to confirm that eating a small amount is easier to tolerate — especially over long periods of time — than full fasting, which is hard to do. Later on, once people reach a target weight, they can transition to ‘maintenance’ by either fasting one day a week, or half-fasting — doubling calories — two days a week.

People generally lose 1–2 pounds per week on the 5:2 diet, so there is an immediate payback, losing over five pounds — and maybe ten — in the first month.

Being a geek, I looked for an app to help me track this, and after rejecting a bunch (without actually trying them) I’ve signed up for Lifesum. One reason is that Lifesum has both web and mobile versions. I really favor doing this sort of thing on a web app. Another reason is that Lifesum supports 5:2 specifically, while at core being a general diet tracking app. Because it supports a wide range of diets, the database of foods and recipes is large, and the likelihood of remaining in business is higher. But with 5:2 specific features, it works for what I want to accomplish.

Yes, I had to upgrade to a paid ‘Gold’ plan for 5:2 support, but fair’s fair. At least it’s supported.


I’ve picked Tuesdays and Thursday for fasting, as you see above.


Above you see what I had planned for breakfast, a 1-egg egg drop soup, made with an egg, a cup of chicken broth, and a smidge of garlic chili sauce. Also a cup of espresso — 0 calories — with a little milk. That’s how I roll, actually: a very standard breakfast for me. The interesting/difficult/unusual part comes later. No lunch, light dinner, and no champagne.

At any rate, I will plan to do a second review of Lifesum in a few weeks, once I have had a little more experience.

Written by

Founder, Work Futures. Editor, GigaOm. My obsession is the ecology of work, and the anthropology of the future.

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