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Study puts new light on weight hazards

Some people obese by BMI had less risk of dying

NEW YORK — A century ago, Elsie Scheel was the perfect woman. So said a 1912 article in The New York Times about how Scheel, 24, was chosen by the ‘‘medical examiner of the 400 ‘coeds’ ’’ at Cornell University as a woman ‘‘whose very presence bespeaks perfect health.’’

At 5-foot-7 and 171 pounds, she would, by today’s medical standards, be overweight. (Her body mass index was 27; 25 to 29.9 is overweight.)

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But a new report suggests that Scheel may have been onto something. The report on nearly 3 million people found that those whose BMI ranked them as overweight had less risk of dying than people of normal weight. And while obese people had a greater mortality risk overall, those at the lowest obesity level (BMI of 30 to 34.9) were not more likely to die than normal-weight people.

The report, although not the first to suggest this relationship between BMI and mortality, is by far the largest and most carefully done, analyzing nearly 100 studies, specialists said.

Specialists not involved in the research said it suggested that overweight people need not panic unless they have other indicators of poor health and that depending on where fat is in the body, it might be protective or even nutritional for older or sicker people. But overall, piling on pounds and becoming more than slightly obese remains dangerous.

“We wouldn’t want people to think, ‘Well, I can take a pass and gain more weight,’ ’’ said Dr. George Blackburn, associate director of Harvard Medical School’s nutrition division.

Rather, he and others said, the report, in The Journal of the American Medical Association, suggests that BMI, a ratio of height to weight, should not be the only indicator of healthy weight.

“Body mass index is an imperfect measure of the risk of mortality,’’ and factors like blood pressure, cholesterol, and blood sugar must be considered, said Dr. Samuel Klein, ­director of the Center for Human Nutrition at Washington University School of Medicine in St. Louis.

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.’’

Specialists also said the data suggested that the definition of ‘‘normal’’ BMI, 18.5 to 24.9, should be revised, excluding its lowest weights, which might be too thin. The study did show that the two highest obesity categories (BMI of 35 and up) are at high risk.

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