(Health.com) -- Being overweight or obese may take years off your life, even if you don't have heart disease or cancer, according to a new study of nearly 1.5 million people.
It might seem obvious that carrying too much weight can pose health risks and contribute to an earlier death. In recent years, however, some studies have suggested that being overweight has no effect on mortality, and may actually reduce the risk of dying at an earlier age.
The findings and size of the new study, which was conducted by researchers at the National Cancer Institute and published in the New England Journal of Medicine, should settle the debate over the relationship between excess weight and the risk of early death, says Ali Mokdad, Ph.D., a professor of global health at the University of Washington, in Seattle.
"Hopefully we can put this to rest and focus on what we need to do in order to help people get healthy and live longer," says Mokdad, who has studied obesity and mortality but was not involved in the new research.
The study authors, led by cancer epidemiologist Amy Berrington, Ph.D., pooled data from 19 previous studies that included 1.46 million white men and women between the ages of 19 and 84.
The link between weight and mortality risk has been difficult to pin down because many studies on the topic have included smokers and people with heart disease, cancer, or a history of stroke -- all of which are related to both obesity and early death. To zero in on obesity, Berrington and her colleagues excluded smokers (current or former) and people who had been diagnosed with those three diseases. (Overweight and obesity were measured using body mass index, or BMI, a simple ratio of height to weight.)
A total of 160,087 people died during the studies, which lasted for an average of 10 years.
Compared with women of normal weight (BMI between 22.5 and 25), overweight women were 13 percent more likely to die during the study period. Moderately obese (BMI 30 to 34) and severely obese (BMI 35 to 39) women were 44 percent and 88 percent more likely to die, respectively, while morbidly obese women (BMI 40+) were 2.5 times more likely to die. The pattern was similar for men.
Underweight people were also at greater risk of dying compared with normal-weight people. However, the researchers say this is likely due to preexisting but undetected illnesses in very thin people, not to serious health problems caused by underweight itself.
"The lowest mortality risks were for the people who had BMIs of 20 to 25," Berrington says. The findings make it clear, she adds, that being overweight is a risk factor for earlier death. "It's a small but statistically significant increased risk."
Even though the study included only white people, the findings likely apply to people of other races, says Mokdad, noting that the researchers took into account a range of health and socioeconomic factors, such as age, physical activity levels, alcohol consumption, education, and marital status.
Berrington says that more research will be needed to confirm that the pattern seen in the study is also found in Asians, African-Americans, and other ethnic groups.
Still, she says, the study -- along with others like it -- should help quiet the theory that being overweight or obese doesn't pose an increased risk of early death. "We now have a very large body of evidence which supports there's an association between overweight and an increased mortality risk," she says.
Copyright Health Magazine 2011