Wednesday, November 7, 2007
The Washington Post reports today on a new study in JAMA showing that
Being overweight boosts the risk of dying from diabetes and kidney disease but not cancer or heart disease, and carrying some extra pounds actually appears to protect against a host of other causes of death, federal researchers reported yesterday. The counterintuitive findings, based on a detailed analysis of decades of government data about more than 39,000 Americans, supports the conclusions of a study the same group did two years ago that suggested the dangers of being overweight may be less dire than experts thought. . . .
"The take-home message is that the relationship between fat and mortality is more complicated than we tend to think," said Katherine M. Flegal, a senior research scientist at the Centers for Disease Control and Prevention in Atlanta, who led the study. "It's not a cookie-cutter, one-size-fits-all situation, where excess weight just increases your mortality risk for any and all causes of death." The study, published today in the Journal of the American Medical Association, was greeted with sharply mixed reactions. Some praised it for providing persuasive evidence that the dangers of fat have been overblown. . . .
But others dismissed the findings as fundamentally flawed, saying an overwhelming body of evidence has documented the risks of being either overweight or obese. "It's just rubbish," said Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health. "It's just ludicrous to say there is no increased risk of mortality from being overweight. . . . From a health standpoint, it's definitely undesirable to be overweight." . . . .
The most surprising finding was that being overweight but not obese was associated only with excess mortality from diabetes and kidney disease -- not from cancer or heart disease. Moreover, the researchers found an apparent protective effect against all other causes of death, such as tuberculosis, emphysema, pneumonia, Alzheimer's disease and injuries. An association between excess weight and nearly 16,000 deaths from diabetes and kidney disease was overshadowed by a reduction of as many as 133,000 deaths from all other deaths unrelated to cancer or heart disease. Even moderately obese people appeared less likely to die of those causes.
Although the study did not examine why being overweight might guard against dying from some diseases, Flegal said other research has suggested that extra heft might supply the body with vital reserves to draw upon to fight illness and aid recovery. . . . .
Now for the downside -
"I think it would be very unfortunate if these findings made us complacent about becoming overweight," said JoAnn E. Manson, chief of preventive medicine at Brigham and Women's Hospital in Boston. "We know being overweight is linked to increased incidence of major chronic disease, including diabetes, hypertension and cardiovascular disease," she said, adding that it "impairs physical function and decreases quality of life." In fact, another paper published in the same journal found that obesity is increasing disabilities among the elderly, making them less able to do simple things such as walk a quarter-mile, climb 10 steps, bend over or lift 10 pounds. Flegal stressed that the findings should not encourage people to be overweight or change any public health recommendations. "This doesn't mean being overweight is good for you," Flegal said. "But it is associated with less mortality than expected."