On Losing Weight

I read something interesting in the December 1 issue of The Economist about weight loss.

Basically, for most of natural history, animals have had to worry about starvation. Only in recent history have living creatures, that is, people in developed countries, had virtually no fear of starvation.

This explains why it's hard to lose weight by simply cutting calories, and easy to gain weight by increasing calories. The body's biochemistry is designed to decrease metabolism when calorie intake falls, thus avoiding starvation. At the same time, people's appetites expand easily to accomodate what's in front of them. This is because the body tries to store fat during times of plenty.

There's a more technical explanation for this in the article itself, but that's the interesting part to me.