People who are overweight at the age of 40 live longer on average than people with other physiques, according to the study conducted by a Japanese Health, Labor and Welfare Ministry research team.

The large-scale study also shows that thin people have the shortest life expectancy, on average dying six or seven years earlier than overweight people.

This remarkable result could ring alarm bells for people overeager to tighten their belts by a few notches and avoid being labeled "metabo," a Japanese term used to describe people with metabolic syndrome.

As part of the study, which was organized by Ichiro Tsuji, a professor at Tohoku University, the team of researchers studied such matters as the health of about 50,000 residents of Miyagi Prefecture age 40 or more over a 12-year period.

The researchers looked at the past physiques of the participants and analyzed the ages they lived to from the age of 40 and grouped them into classifications of body mass index (BMI), an indicator of how fat a person is.

The results showed that men of regular weight (with a BMI of between 18.5 and 25) at age 40 live for an additional average of 39.94 years, while those who are overweight (BMI of between 25 and 30) at age 40 live for a further 41.64 years. Women of regular weight live on average for a further 47.97 years, compared with overweight women_who live another 48.05 years, according to the study.

Obese men and women (BMI of 30 or more) live a further 39.41 and 46.02 years, respectively. But thin men (BMI of less than 18.5) are on average expected to live 34.54 more years, and thin women another 41.79 years, the study showed.

Possible explanations as to why thin people could die earlier include the fact that many thin people smoke and a theory that underweight people are more susceptible to contagious diseases.

However, the link between physique and life expectancy is not clearly understood. Shinichi Kuriyama, an associate professor at Tohoku University who led the actual research, warns that "people won't extend their lives by straining to put weight on."

But the study also found that the fatter a person is, the greater their medical expenses.

The average lifetime medical expenses for obese people from the age of 40 is 15.21 million yen ($158,000) for men and 18.6 million yen ($193,000) for women _ both 30 percent higher than for thin people.

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(c) 2009, The Yomiuri Shimbun.

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