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Being overweight causes some well-known health problems, but it is not necessarily all bad either, federal researchers say in a disputed study.

A detailed analysis of decades of data on more than 39,000 Americans reveals that carrying a few extra pounds might be less onerous than once thought. The analysis supports the conclusions of a study from the same group two years ago. This latest study was published last week in the Journal of the American Medical Association.

One positive sign? Being overweight does not raise the risk of dying from cancer or heart disease. It also appears to have a protective effect against other causes of death, such as tuberculosis, emphysema and pneumonia. Researchers used widely accepted federal definitions of “overweight” and “obesity.” A body mass index of between 25 and 30 classifies someone as overweight, while above 30 as obese.

Some experts harshly criticized the findings, citing “flawed” methodology and citing what they saw as overwhelming evidence to the contrary.