While health experts have long been warning of the dangers of obesity, a new Japanese study warns that being very skinny is far more dangerous and shows that slightly chubby people actually live longer.

A long-term study of middle-aged and elderly people by the Tohoku University's Graduate School of Medicine showed that people who are a little overweight at age 40 life six to seven years longer than very thing people, whose average life expectancy was a good five years shorter than that of obese people.

Shinichi Kuriyama, an associate professor who worked on the study, said:

"We found skinny people run the highest risk. We had expected thin people would show the shortest life expectancy but didn't expect the difference to be this large."

He continued:

"There had been an argument that thin people's lives are short because many of them are sick or smoke. But the difference was almost unchanged even when we eliminated these factors."

The primary reasons skinny people were believed to have shorter lifespans include heightened vulnerability to diseases such as pneumonia and the fragility of their blood vessels.

Kuriyama was quick to warn, however, that he was not recommending people eat as much as they want:

"It's better that thin people try to gain normal weight, but we doubt it's good for people of normal physique to put on more fat," he said.

The study included 50,000 adults between the ages of 40 and 79 over twelve years in the northern Japanese prefecture of Miyagi.