If you asked me this question — why did this restaurant get crowded? — and I said, well, the restaurant got crowded (it got overstuffed with energy) because more people entered the restaurant than left it, you’d probably think I was being a wise guy or an idiot. (If I worked for the World Health Organization, I’d tell you that “the fundamental cause of the crowded restaurant is an energy imbalance between people entering on one hand, and people exiting on the other hand.”) Of course, more people entered than left, you’d say. That’s obvious. But why? And, in fact, saying that a restaurant gets crowded because more people are entering than leaving it is redundant –saying the same thing in two different ways – and so meaningless.
Now, borrowing the logic of the conventional wisdom of obesity, I want to clarify this point. So I say, listen, those restaurants that have more people enter them then leave them will become more crowded. There’s no getting around the laws of thermodynamics. You’d still say, yes, but so what? Or at least I hope you would, because I still haven’t given you any causal information. I’m just repeating the obvious.
This is what happens when the laws of physics (thermodynamics) are used to defend the belief that overeating makes us fat. Thermodynamics tells us that if we get fatter and heavier, more energy enters our body than leaves it. Overeating means we’re consuming more energy than we’re expending. It’s saying the same thing in a different way. (In 1954, the soon-to-be-famous — and often misguided, although not in this case — nutritionist Jean Mayer said that to explain obesity by overeating was about as meaningful as explaining alcoholism by overdrinking, and merely reaffirmed, quite unnecessarily, the fact that the person saying it believed in the laws of thermodynamics.) Neither happens to answer the question why. Why do we take in more energy than we expend? Why do we get fatter?
That’s Gary Taubes in a post from late last year. The post is worth a full read.