The largest, and what experts are calling the most carefully done, study of the link between body mass index and health risks has concluded that people deemed "overweight" have lower mortality risk than those who have a BMI in the "normal" range (Source: "Study Suggests Lower Mortality Risk for People Deemed to Be Overweight," New York Times, Jan. 1, 2013).
While the study, published in the Journal of the American Medical Association, does not dismiss the dangers of obesity, it concluded that BMI, a ratio of height and weight, should not be used as the sole indicator of health. Researchers found that while those in the two highest obesity categories (B.M.I. of above 30 and above 35) are at the highest mortality risk, those in the "overweight" category (a BMI of 25 to 29.9) had "significantly lower all-cause mortality" than those in the normal BMI range.
The researchers said that their findings indicate that other health risk factors need to be considered along with weight, and where the fat is on the body also matters.
Dr. Steven Heymsfield, executive director of the Pennington Biomedical Research Center in Louisiana, who wrote an editorial accompanying the study, said that for overweight people, if indicators like cholesterol “are in the abnormal range, then that weight is affecting you,” but that if indicators are normal, there’s no reason to “go on a crash diet.”
Experts also said the data suggested that the definition of “normal” B.M.I., 18.5 to 24.9, should be revised, excluding its lowest weights, which might be too thin.