Seriously obese people may lose ten years off their life and moderately obese people may lose three according to the largest study ever conducted on how obesity affects mortality.
The study by Oxford University researchers and published this week in The Lancet medical journal, is a new analysis of 57 separate studies conducted mostly in North America and Europe, reports The Guardian. Researchers examined the body mass index (BMI) of nearly 900,000 people, most of whom were 46 in 1979 when the study started and had an average BMI of 25. A BMI of 18.5 to 24.9 is considered normal, 25 to 29.9 is overweight, and 30 or more is classified as obese.
Researchers followed the group for 20 years, during which time 100,000 people died. Men and women with a BMI between 22.5 and 25 were least likely to die during the study, but ever additional 5 GMI points reduced their mortality rate by 30 percent. The group with the lowest mortality rate had a BMI of 24. People who had a BMI of 30 to 35, considered moderately obese, died three years earlier than would be expected at a healthy weight. Those who were severely obese, with a BMI of 40 to 50 cut their lifespan by 10 years, about the same as is estimated for smokers.
Though severe obesity only affects about 2% of the population, in the United States 66% of adults are either overweight or obese, according to CNN. "What is particularly worrisome in the United States is that more than a third of people now qualify as obese, and a subset of people are becoming progressively more obese," says Michael Thun, emeritus vice president of epidemiological research at the American Cancer Society, who did not work on the study. Thun said that while obese people should focus on not continuing to gain weight and quitting smoking, since both smoking and severe obesity take an average of 10 years off your life. "There has been an artificial horse race between obesity and smoking over which is worse. This is fundamentally silly," says Thun. Oxford University professor Richard Peto, who worked on the study, stressed that it should not be interpreted to mean that smoking is less dangerous. "These are two things that you do have any choice about," Peto said. "I think smokers are getting the wrong message if they keep on smoking and think what matters is obesity. Smoking matters enormously more."