[Photo by Meng Zhongde/Asianewsphoto]

If you want to have a longer life expectancy, advices from researchers are: keep weight down, don't smoke and drink alcohol moderately.

A study of the University of Michigan (UM) shows that people of fairly normal weight who never smoked and only drank moderately at age of 50 have a life expectancy that is seven years longer than the average American.

These people can also delay disability up to six years.

Using data from UM's Health and Retirement Study of Americans aged 50 and older that began in 1992, and with research sample in 1998 including nearly 15,000 respondents aged 50-74, the researchers at UM defined the low-risk category as those who never smoked, drank moderately and had a body mass index that was less than the classification for obese (30+).

For definition of drinking moderately, it is fewer than 14 drinks per week for men and fewer than 7 drinks per week for women.

The researchers found that non-obese people who had quit smoking for 10 years prior to the study and who drank moderately had overall and disability-free life expectancies that were only one year shorter than non-obese people who had never smoked and drank moderately.

"It's important to convince people to improve these behaviors in order, not only to live a longer life, but live a long life free of disability," said Neil Mehta, assistant professor of health management and policy at the UM School of Public Health.

Of course, people who have avoided these unhealthy behaviors are not the norm. "80 percent of Americans in their 50s either have smoked or been obese. That's huge," Mehta said. "Our study speaks to the importance of prevention at whatever level that can occur in community health or in public policy."

Current life expectancy in the US is about 78 years for men and 82 years for women. But for the low-risk group, they are 85 and 89, respectively.

The study is believed to be the first to show the effect of all three factors combined.