美国国家公共电台 NPR Carrying Some Extra Pounds May Not Be Good After All（在线收听）

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The dangers of obesity are well known. The dangers of carrying a little extra weight, though, are the subject of more debate. NPR's Patti Neighmond reports that a new study published this week in the Annals of Internal Medicine says being slightly overweight could actually shorten lifespan.

PATTI NEIGHMOND, BYLINE: Nobody's arguing about the dangers of obesity, which increases risk for diabetes, heart disease, certain cancers and even premature death. The debate here is about people who are overweight, but not obese. And that's a lot of people, says Dr. Steven Heymsfield, an obesity researcher at the Pennington Biomedical Research Center in Baton Rouge.

STEVEN HEYMSFIELD: People who are overweight generally know it. Their belt's a little tight. Their clothes don't fit as well as they used to. And I think most people who fall within that range have a pretty good sense that they're a few pounds overweight, but they're not quite obese.

NEIGHMOND: A body mass index, or BMI, over 25 is considered overweight. About one-third of Americans are overweight. Another 40 percent are considered obese. In the study, researchers looked at information gathered on more than 225,000 adults over 50. They wanted to know if being overweight affected lifespan. Demographer Andrew Stokes at Boston University School of Public Health headed the study, which found, yes, it did. There was a 6 percent increased risk of death among individuals who were overweight.

ANDREW STOKES: For this group, we found consistently across the board for all the causes of death examined that having a history of overweight over the 16-year period was associated with increased risk of death.

NEIGHMOND: Six percent is only a modest increase, he says, but it's worrisome because so many Americans are overweight. Now, the findings are also provocative because they seem to contradict earlier research published four years ago by Stanford University epidemiologist Katherine Flegal. At the time of her study, she was with the CDC.

KATHERINE FLEGAL: In our meta-analysis, we had 97 studies. And the combined effect of all those studies was to show a slight decrease in mortality in the overweight category relative to the normal weight category.

NEIGHMOND: So being overweight seemed to be protective. It's not clear why. Some doctors speculate it could be a little extra fat protects people if they fall or offers an energy reserve during illness. Researcher Stokes says his findings of increased risk of death among overweight people are more reliable because they examined weight over 16 years. And he says that makes the take-home message pretty clear.

STOKES: Individuals should try as hard as possible to maintain a weight in the normal range for as large a portion of their adult life as possible.

NEIGHMOND: Stokes says future research should look at whether an overweight person who diets, exercises and loses weight can turn back their risk of disease to that of an individual who never gained weight in the first place. In the midst of conflicting findings, researchers Steven Heymsfield says people who are overweight should check with their doctor to see if they have other weight-related health problems.

HEYMSFIELD: For example, is your blood sugar high? Is your blood pressure high? Is your cholesterol too high? If so, then you should consider treatment for those risk factors...

NEIGHMOND: ...Which all have effective treatments. At the same time, Heymsfield says, people should work hard to prevent future weight gain and, if so motivated, lose weight and try to bring their BMI down to a healthier level. Patty Neighmond, NPR News.

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