Being obese can take years off your life and, in some cases, can be as dangerous as smoking, a new study says. British researchers from the University of Oxford analyzed 57 studies, mainly in Europe and North America, following almost a million people for an average of 10 to 15 years. During that time, about 100,000 of those people died.
The studies used the body mass index (BMI), a measure that divides a person’s weight in kilograms by their height in meters squared to determine obesity. The researchers found that death rates were lowest in people with a BMI of 23 to 24, on the high side of the normal range.
Health officials generally define overweight people as those with a BMI of 25 to 29, and obese people as those with a BMI greater than 30.
The study was published online Wednesday in the medical journal Lancet. It was paid for by the Medical Research Council of Great Britain, the British Heart Foundation, Cancer Research UK and others.
“If you are heading towards obesity, it may be a good idea to lose weight,” said Sir Richard Peto, the study’s lead statistician and a professor at Oxford University.
Peto and his colleagues found that moderately overweight people, with a BMI of 30 to 35, lost about three years of life. Morbidly overweight people (those with a BMI greater than 40) lost around 10 years of their life expectancy, similar to the effect of lifetime smoking.
Moderately obese people were 50 percent more likely to die prematurely than people of normal weight, said Gary Whitlock, the Oxford University epidemiologist who led the study.
He said obese people were also two-thirds more likely to die of a heart attack or stroke, and up to four times more likely to die of diabetes, kidney or liver problems. They were one sixth more likely to die of cancer.
“This really emphasizes the importance of weight gain,” said Dr. Arne Astrup, a professor of nutrition at the University of Copenhagen who was not linked to the Lancet study. “Even a small increase in your BMI is enough to increase your risks for cardiovascular disease and cancer.”
Previous studies have found that death rates rise both above and below a normal BMI score, and that people who are moderately overweight live longer than people who are underweight or normal weight.
Other experts said that because the documents used in the study mostly began between 1975 and 1985, their conclusions were not as relevant today.
Astrup worries that rising obesity rates could reverse the sharp drops in heart disease seen in the West.
“Obesity is the new dark horse for public health officials,” he said. “People need to be aware of the risks they run when they gain weight.”