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Is there an “obesity paradox” in diabetes?

NEW YORK (Reuters Health) – Overweight and obese people tend to live longer than normal-weight people after a diagnosis of type 2 diabetes, a new meta-analysis shows.

This so-called “obesity paradox” has been observed before in chronic diseases like heart and kidney failure, said Dr. Mercedes R. Carnethon of the Feinberg School of Medicine at Northwestern University in Chicago, who led the study.

It’s probably not that excessive pounds are protective, said Dr. Carnethon, but rather that lean people who get diabetes are somehow predisposed to poorer health. “Perhaps those individuals are somehow genetically loaded to develop diabetes and have higher mortality,” she said. “A normal-weight person who has diabetes has an extremely high mortality rate.”

The new findings, released online today in the Journal of the American Medical Association, are based on data from five longitudinal cohort studies. More than 2,600 participants in the studies developed type 2 diabetes, and 12% had a normal weight when they got the diagnosis.

The mortality rate was 1.5% per year among overweight and obese people, compared to 2.8% per year among their trimmer peers.

After accounting for several risk factors for heart disease – including age, blood pressure, high cholesterol and smoking status – lean people were more than twice as likely to die at any given point as heavier people. The same held true for deaths caused by heart disease.

“It was a little bit unexpected to see that,” said Dr. Carnethon.

One potential limitation of the study is that the researchers couldn’t always account for how much people smoked. It’s also possible that a few people might have been diagnosed with diabetes outside of the studies and been told to slim down by their own doctor before they were seen by the study researchers.

Older people and people of Asian descent are more likely to be normal-weight when diagnosed with diabetes, and Dr. Carnethon stressed that doctors need to take the disorder extra seriously when it’s not accompanied by obesity.

“These findings do apply to a growing segment of the population,” she said.

SOURCE: http://bit.ly/NAmBd2

JAMA 2012.