Monday, March 16, 2015

The Dieting Mirage

Every day you eat three to five pounds of food - where does it go? Most of it is (or is metabolised to) water which leaves the body as sweat, moist breath or liquid waste. Between half a pound and a pound is excreted as solid waste (eat more fibre!). The remainder is exhaled as yet another metabolic by-product - carbon dioxide. Oh, and maybe some of it adds to your unsightly girdle of fat!

Remember conservation of mass?

Suppose you go on a diet; you reduce your day's food intake by 1,000 Calories (i.e. half rations). Next day you weigh yourself. Triumph! ... you weigh a pound or two less!

So now it's an eating day again. Next day, omigod ... you've gained two pounds!

This is not a story of yo-yo dieting. You're weighing differences in internally-carried food!*

A pound of fat provides around 3,000 Calories. If you reduce your daily intake by 1,000 Calories you will metabolise of the order of one third of a pound of fat to compensate. Honestly, you will not notice this on the scales. If you can maintain a 1,000 Calorie daily deficit for a whole week (a big ask!) you might lose that magic two pounds for real - something noticeable behind the daily ups and downs of eat-process-excrete! Think incremental, marginal gains and stick at it.

* I don't think we should forget the gut microbiome either. Weighing in at two to three pounds, it seems plausible that this mass of symbiotic bacteria should be quite responsive to levels of nutrition, dying back when the host is dieting and re-expanding once the good times return. This additional (non-fat related) ebb and flow of weight probably occurs on a timescale of some days: yet another delayed reaction to dietary change.


And now for something completely relaxing: take your shoes off, lean back and just chill with this ...

Thanks to Marginal Revolution.


In other stuff, we have not seen the painter for some days after an initial half day of preliminary wall-scraping, an absence due entirely to rain and inclement winds. We hope to see him again tomorrow.

Free Energy is a thermodynamics concept: it's the amount of energy in a system which can do useful work. It's the reason why only differences in temperature can power machines like steam engines: a uniformly warm heat-bath can't make anything work. This has (negative) implications for life in the outer solar system. Remember Europa in the book/film 2001?

How do we know it's Spring? A vole's head, tail and unidentifiable lump on the kitchen floor yesterday morning + the animal has taken to ambush-hunting birds in the bushes under the feeders. Just thought I'd share ...