(Agencies)
Updated: 2007-11-08 22:49

NEW YORK -- Being overweight is not all bad, carrying some excess pounds actually appears to protect against some causes of death, according to a US federal research published Wednesday in the Journal of the American Medical Association.

A girl does sit-ups at a summer camp for overweight children, organized by Gangseo district office, in Seoul July 27, 2006. Being overweight is not all bad, carrying some excess pounds actually appears to protect against some causes of death, according to a US federal research. [Agencies]

In the new research, the analysis is based on the health statistics that federal scientists collected between 1971 and 2004, including cause-of-death data from 2.3 million adults from 2004.

The researchers used widely accepted federal definitions of "overweight" and "obesity" based on body mass index. A body mass index, or BMI, of between 25 to 30 classifies someone as overweight and above 30 as obese.

The most surprising finding was that being overweight but not obese was associated only with excess mortality from diabetes and kidney disease -- not from cancer or heart disease.

Moreover, the researchers found an apparent protective effect against all other causes of death, such as tuberculosis, emphysema, pneumonia Alzheimer's disease and injuries.

"The take-home message is that the relationship between fat and mortality is more complicated than we tend to think," said Katherine M. Flegal, a senior research scientist at the Centers for Disease Control and Prevention in Atlanta, who led the study.

Though the study did not examine why being overweight might guard against dying from some diseases, Flegal said earlier researches have suggested that extra heft might supply the body with vital reserves to draw upon to fight illness and aid recovery.

In the United States, some two-thirds of the population are classified as overweight, including about one-third who are obese.

Flegal said the new findings should not encourage people to be overweight or change any public health recommendations.

"This doesn't mean being overweight is good for you," Flegal said. "But it is associated with less mortality than expected."