Little extra weight may not be bad

WASHINGTON — Being overweight boosts the risk of dying from diabetes and kidney disease but not cancer or heart disease, and carrying some extra pounds appears to protect against some other causes of death, federal researchers reported Tuesday.

The findings, based on an analysis of decades of government data about more than 39,000 Americans, suggest being overweight carries risks but the dangers may be less dire than experts thought.

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

The study, published in the Journal of the American Medical Association, was greeted with mixed reactions.

"What this tells us is the hazards have been very much exaggerated," said Steven Blair, a professor of exercise science, epidemiology and biostatistics at the University of South Carolina.

But others dismissed the findings as flawed, saying an overwhelming body of evidence has documented the risks of being either overweight or obese.

"It's just rubbish," said Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health. "It's just ludicrous to say there is no increased risk of mortality from being overweight."

It was the second study by the same government scientists who two years ago first suggested that deaths from being too fat were overstated.

The new report further analyzed the same data, this time looking at specific causes of death along with new mortality figures from 2004 for 2.3 million U.S. adults.

The researchers used widely accepted federal definitions of "overweight" and "obesity" based on body mass index (BMI). Under that system, a BMI of 25 to 29.9 defines someone as overweight and a BMI of 30 or higher defines someone as obese.

The researchers found that obesity raised the risk of death from heart disease, diabetes and kidney disease, and several cancers previously linked with excess weight, including breast, colon and pancreatic cancer.

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

Researchers also found an apparent protective effect against all other causes of death, such as tuberculosis, emphysema, pneumonia, Alzheimer's and injuries.

Although the study did not examine why being overweight might guard against dying from some diseases, Flegal said other research has suggested extra heft might supply the body with vital reserves to draw upon to fight illness and aid recovery.

"You may not just have more fat. You may also have more lean mass, more bone and muscle," Flegal said. "If you are in an adverse situation, that could be good for you."

Obesity researcher Barry Popkin of the University of North Carolina, Chapel Hill, noted the study "is about death. This is not about health and sickness."

It doesn't address whether cancer and heart disease occur more often in overweight people, something that has been suggested by other research.

Material from The Associated Press is included in this report.