It was welcome because obesity begins early — people obese from age 3 to 5 are five times more likely than others to be overweight or obese as adults, when being so makes people more susceptible to cancer, heart disease and stroke. It was a surprise because no one knows why the rate dropped.

A reasonable surmise, however, is that one cause is the cumulative effect of talk about sensible eating and exercising. Certainly one lesson of the past 50 years is that one of the most cost-effective things government does is disseminate public health information concerning behaviors as disparate as smoking and using seat belts.

Mark Twain said humans are the only animals that blush — or need to. Leon Kass, a University of Chicago professor emeritus now at the American Enterprise Institute, has written that humans are the only animals that do not “instinctively eat the right foods (when available) and act in such a way as to maintain their naturally given state of health and vigor. Other animals do not overeat, under-sleep, knowingly ingest toxic substances, or permit their bodies to fall into disuse through sloth, watching television and riding in automobiles, transacting business, or writing articles about health.”