The study was conducted by Dutch researchers and published in Tuesday's issue of the Annals of Internal Medicine.
Nonsmokers who were classified as overweight, but not obese, lost an average of three years off their lives. Obese people died even sooner. Obese female nonsmokers lost an average 7.1 years, while men lost 5.8 years.
Scientists have long known that overweight people have shorter life expectancies, but few large-scale studies have been able to pinpoint how many years they lose.
"This study is saying that if you are overweight by your mid-30s to mid-40s, even if you lose some weight later on, you still carry a higher risk of dying," said Dr. Serge Jabbour, director of the weight-loss clinic at Thomas Jefferson University Hospital in Philadelphia. "The message is that you have to work early on your weight. If you wait a long time, the damage may have been done."
For smokers, the results were even worse. Obese female smokers died 7.2 years sooner than normal-weight smokers, and 13.3 years sooner than normal-weight nonsmoking women. Obese male smokers lived 6.7 years less than trim smokers, and 13.7 years less than normal-weight nonsmokers.
The results were culled from vital statistics collected from 3,457 volunteers in Framingham, Mass., from 1948 to 1990. The data were analyzed by researchers at Erasmus Medical Center and the University of Gronigen in the Netherlands.
Obesity is defined as having a body-mass index of 30 or above. The index is a measure of weight relative to height. Healthy weight is a BMI of less than 25.
About two-thirds of U.S. adults are overweight or obese, according to the Centers for Disease Control and Prevention. Studies have also shown that people are getting fatter, younger.
"The smoking epidemic in the Western world is waning; however, a new fear should be the increasing prevalence of overweight and obesity in young adults, which heralds another potentially preventable public health disaster," the researchers said.
By DAVID B. CARUSO