People who are overweight at 40 not only have a higher risk for chronic diseases such as diabetes, but they could also be robbed of at least three years of life, according to a new study.

Dutch researchers looked at medical records from 3,457 volunteers in Framingham, Mass., from 1948 to 1990.

They found among those who become obese by age 40, obesity shortened their life expectancy to the same degree as smoking.

Adults are defined as obese if they weigh over 20 per cent more than the maximum healthy body weight.

The results suggest obese, male smokers were the worst off, losing 13.7 years of life compared to trim nonsmoking males. Obese, female smokers lost 13.3 years on average, the researchers found.

Nonsmokers who were considered overweight by age 40 had their lives shortened by 3.3 years for women and 3.1 years for men.

Researchers at Erasmus Medical Center and the University of Gronigen in the Netherlands analysed the data for the study, which appears in Tuesday's issue of the Annals of Internal Medicine.

In 1998, 47.9 per cent of Canadians were overweight, according to Statistics Canada. The Centers for Disease Control and Prevention say about two-thirds of adults in the U.S. are overweight or obese.

The researchers note smoking is waning in the western world.

"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 study's authors warned.