Your excess fat eats (some of) your excess food

I have this recurring nightmare. I indulge myself with that delicious but superfluous baguette for lunch -- tomato and thick slices of brie, with perhaps a caramel bar to follow - and slowly and surely I'm going to blow up.

All those years of 5:2 fasting and self-denial put to waste.

But it won't happen - at least, not to infinite weight. The extra fat is real but surely it's self-limiting: after all, it metabolises. That extra fat needs extra calories. A new equilibrium will be born.

The health-police don't want you to know this, but a quick back of the envelope calculation makes it clear.

They say men should consume 2,500 calories per day and women 2,000. Notice that the larger bodies of men already require more calories to maintain themselves. Apparently, the average UK man weighs 84 kg while the average UK woman weighs 70 kg.

And so we get get this rough-and-ready graph.

We're ignoring the differences between bone, muscle and fat plus the fact that women have a third more fat in their bodies than men. If we had it right, the constant would be zero.

But, just roughly, if you eat an extra 360 calories a day (my superfluous lunch) then your equilibrium weight will be pushed up by .. 10 kg.

Oops! A price not worth paying!

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In fact my weight has gone up from its target 67 kg to almost 69 kg since Christmas.

Could I be consuming (36 *2 =) 70 calories a day too much? No, nothing so benign.

Building this extra weight (gaining 1 kg of fat = 7,700 calories) is far more expensive than simply maintaining it (maintaining 1 kg of fat = 36 calories/day).

I think I see what that baguette has been doing .. and why expansion might not stop anytime soon .. .