The genetic limits of obesity.

If, at 17 percent, we've hit the "saturation" point for child obesity, we're extremely lucky. There's no historical basis for knowing where the saturation point is, since our species has never before lived in an environment so full of ease and abundance. The far more dangerous possibility is that the saturation point is higher. In fact, given that we evolved in conditions of scarcity, it's logical to suspect that the tendency to seek and store fat is nearly universal. As the Los Angeles Times observes, "the idea that childhood weights have simply topped out doesn't quite square ... [One expert] said the fact that 60% of U.S. adults were either overweight or obese suggested that children had plenty of room to grow."

Two years ago, when I was researching the global escalation of obesity, I came across the work of Barry Popkin, an epidemiologist who studies obesity and hunger at the University of North Carolina. He's the guy who laid out the theory of how progress has changed our causes of death. In the hunter-gatherer era, if we didn't find food, we died. In the agricultural era, if our crops perished, we died. In the industrial era, famine receded, but infectious diseases killed us. Now we've achieved such control over nature that we're dying not of starvation or infection, but of abundance.

You want a really scary explanation for the plateau in child obesity? Part of it, according to Popkin, may be economic. "When economic times are difficult, we always slow things down on lots of things, like eating," he told the Post.

In other words, as the economy recovers and advances, so will obesity. And nobody knows where it'll end.

So let's stop "congratulating" ourselves for "trying to do good things" and "make a difference" in the fight against obesity. Let's pray that a force stronger than human will is behind the current stabilization. Doing good is less important than being well.