ACCORDING to the United States government, nearly 7 out of 10 American adults weigh too much. (In 2010, the Centers for Disease Control and Prevention categorized 74 percent of men and 65 percent of women as either overweight or obese.)

But a new meta-analysis of the relationship between weight and mortality risk, involving nearly three million subjects from more than a dozen countries, illustrates just how exaggerated and unscientific that claim is.

The meta-analysis, published this week in The Journal of the American Medical Association, reviewed data from nearly a hundred large epidemiological studies to determine the correlation between body mass and mortality risk. The results ought to stun anyone who assumes the definition of “normal” or “healthy” weight used by our public health authorities is actually supported by the medical literature.

The study, by Katherine M. Flegal and her associates at the C.D.C. and the National Institutes of Health, found that all adults categorized as overweight and most of those categorized as obese have a lower mortality risk than so-called normal-weight individuals. If the government were to redefine normal weight as one that doesn’t increase the risk of death, then about 130 million of the 165 million American adults currently categorized as overweight and obese would be re-categorized as normal weight instead.