Indeed, one expert cautioned that body weight alone cannot predict health and the risk of death.
"There are other factors that play a role in overall health," said Dr. William Cefalu, chief and professor of the section of endocrinology, diabetes and metabolism at Louisiana State University and co-author of an accompanying journal editorial.
"Body mass index simply is a parameter; it doesn't take into consideration family history, it doesn't take into consideration smoking, fitness, cholesterol and other factors that should be considered beyond body mass index," he said.
Another expert agreed and added that the issues around body weight are more complicated than this study suggests.
"This is a large, sophisticated and statistically powerful study that shows convincingly that more severe degrees of obesity increase the risk of premature death, while being merely overweight does not," said Dr. David Katz, the director of the Yale University Medical School Prevention Research Center.
"Like the study itself, the messages here are a bit complex," Katz added.
There is a case to be made that a body mass index in what is now considered the overweight range might be redefined as normal, Katz said. "If weight is not harmful to health, there is no reason to suggest otherwise," he said.
This study, however, looks only at death, not chronic medical conditions, Katz noted.
"It may well be being overweight does increase the risk of such conditions as type 2 diabetes, or medication use for cardiac risk factors, without increasing mortality. This study would be blind to such effects," he said.
Katz also noted the trends in obesity may be tipping the scale toward increased risk of dying. "Rates of overweight and obesity overall appear to be stabilizing, while rates of severe obesity are rising brisk
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