Today is a beautiful day for a run in New York’s Central Park — sunny and cool, with the trees wearing the first pale-green lushness of early spring. My wife and I were jogging around the park, pushing our 1.5-yr-old in a jogging stroller, and lamenting the difficulty we’ve been having getting our weight down, even though we’ve been exercising a good deal more now that the weather has gotten nice.
Sandra, it turned out, had just been reading an article in the New York Times Sunday Magazine about just this very topic. Gretchen Reynolds delves into the issue of exercise and weight loss, and the discouraging research that has found that, for women especially, exercising more makes you hungrier, so you eat more and wind up counteracting the calorie-burning you’ve been doing. Writes Reynolds:
In practical terms, the results are scientific proof that life is unfair. Female bodies, inspired almost certainly “by a biological need to maintain energy stores for reproduction,” Braun says, fight hard to hold on to every ounce of fat. Exercise for many women (and for some men) increases the desire to eat.
Upon hearing this information, I was of two minds. On the one hand, I was pleased to have an explanation for this annoying phenomenon. On the other hand, I thought: is the urge to find explanations for our behavior ultimately self-defeating?
For every failure of self-control, evolutionary psychology can offer a plausible explanation for why it must be so. Is your husband cheating? It’s because during the stone age natural selection favored males who reproduced as fervently as possible. Does your wife shop too much? It’s because stone-age womenfolk needed a deep-seated instinct to gather. Are you fat? It’s because your stone-age ancestors needed to crave fat in order to get through the winter.
The problem is that, having sought out reasons for our behavior, we are left in possession of an explanation that is, if anything, too powerful. What we wanted to know was why controlling our behavior was so difficult; what evolutionary explanations tell us is why control is impossible. And in so doing they fail us twice over.
First, because we haven’t always been been this way. The obesity epidemic, for instance, is something that has only sprung up in the last 20 years. If evolution wants us to crave high-calorie foods, then why weren’t we fat in the ’70s?
The second way these explanations fail us is that, having armed us with the knowledge that our genes condemn us to bad behavior, they powerfully demotivate us from improving.
So I tell my wife, forget that evolution wants you to gain weight so that you can bear more children. Keep exercising, keep trying to eat better, and we’ll do the do the best we can.