A little extra weight may not help you live longer after all
Popular notion gets new scrutiny
Bad news, overweight Americans. There’s no survival advantage to carrying a few extra pounds, the latest research suggests.
The study, published Monday in Annals of Internal Medi
cine, casts doubt on the popular idea, supported by some previous studies, that people who are overweight, but not obese, live longer than their thinner peers. Those studies also found that even mild obesity might not raise death rates, despite links to heart disease, diabetes and cancer — the “obesity paradox.”
Some researchers have been skeptical about those findings, and the new study, using new methodology, gives them ammunition. It finds that the fatter we get, the more likely we are to die young from any cause, and particularly from heart disease, cancer or respiratory disease.
“Overall, for the population as a whole, the increased risk associated with overweight is modest” compared to the risk of outright obesity, said lead researcher Andrew Stokes, an assistant professor of global health at Boston University. But, he said, the risks are higher among some groups, including those under age 70.
About one-third of U.S. adults are overweight and another third are obese, according to the federal Centers for Disease Control and Prevention. Those categories are based on body mass index (BMI), a measurement that combines height and weight and is a rough indicator of body fat. A BMI of 18.5 to 24.9 is considered normal weight; 25 to 29.9 is overweight; 30 and over is obese.
A 5-foot 9-inch adult becomes overweight at 169 pounds and obese at 203 pounds.
The debate over whether those categories reflect real health differences was jolted in 2013, when CDC researchers combined 97 studies and found slightly lower death rates in overweight people than in normal-weight peers. Only BMIs above 35 were clearly associated with death.
But that study looked at weight at just one point in time. That left open the possibility that deaths among once-fat people who lost weight because of fatal illnesses were counted in the normalweight category, Stokes said.
In the new study, he and his colleagues tried to overcome that flaw by looking at 16 years of weight history among 225,072 adults surveyed repeatedly in earlier studies. Then they counted deaths for more than a decade after the last weight reports. They found elevated death rates among those who had been overweight or obese at any point — ranging from a 1% increase for the overweight to a 73% increase for the severely obese.
The highest death counts were among those who were once overweight or obese, then lost a lot of weight, Stokes said.
And, because successful intentional weight loss is so rare, it is likely that most of them lost weight because of illness, he said. Other research strongly suggests intentional sustained weight loss is healthy, he added.
Despite the new findings, the debate over the fate of the overweight continues.
“To me, it doesn’t change the picture,” said Katherine Flegal, a former CDC researcher who led the 2013 study and is now a consulting professor at Stanford University.
The studies, taken together, suggest being overweight has no big positive or negative effects, she said. And the new study assumes, but does not prove, that illness explains any death risk linked to thinness, she added. She also noted that weights and heights in the new study were self-reported, not checked by researchers.
In any case, she said, BMIs are just “ballpark categories,” and “if you want to know someone’s health risks, you should measure their blood pressure, measure their cholesterol, check their blood sugar.”
The latest findings cast doubt on what had become known as the “obesity paradox.”