Is it True that Overweight People Live Longer?

Diabetes. Cancer. Heart disease. Stroke. Extra pounds raise the risk of nearly every health threat facing Americans. Yet, the Journal of the American Medical Association (JAMA) published—and publicized—a study suggesting that overweight people live longer.
“It’s extremely frustrating,” says Michael Thun, vice president emeritus for surveillance and epidemiology research at the American Cancer Society. “It perpetuates a myth.” Here’s how.

At first glance, the new JAMA study seems impressive.

The CR Diet Truth: Will Calorie Restriction Prolong your Life?

“We’ve known for a long time that if you reduce the calorie intake of rats or mice, they live much longer,” says Mark Mattson, chief of the laboratory of neurosciences at the National Institute on Aging (NIA) in Baltimore.

What happens in species closer to humans is more complicated. Rhesus monkeys fed 30 percent fewer calories lived longer in a study at the University of Wisconsin, but not in a study at the NIA.

Why the different results? One possibil­ity: The Wisconsin monkeys were fed few­er calories than monkeys fed as much high-sugar, high-fat food as they want­ed. In contrast, the NIA monkeys were fed fewer calories than monkeys fed as much (low-sugar, low-fat) food as they needed to maintain their weight.