After more than 10 years of follow-up, normal-weight patients at the time of diabetes incidence had a twofold greater hazard for total mortality (HR 2.08, 95% CI 1.52 to 2.85) as compared with overweight or obese individuals. Obesity and diabetes might not be the double whammy you’d expect, according to a fresh look at older studies.
Surprisingly, researchers found that overweight and obese people who get diagnosed with the blood sugar disorder tend to live longer than their leaner peers.
This so-called "obesity paradox" has been observed before in chronic diseases like heart and kidney failure, said Mercedes R. Carnethon of the Feinberg School of Medicine at Northwestern University in Chicago.
Carnethon added that, it doesn’t mean you should start downing ice cream and other high-calorie foods if you just found out you have diabetes. Nor does it mean that padding your waist is a good way to improve your prognosis before you get the disease.
In fact, it’s probably not that excessive pounds are protective, said Carnethon, but rather that lean people who get diabetes are somehow predisposed to worse 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 are based on data from five earlier studies that tracked people over time to identify risk factors for heart disease. More than 2,600 participants developed type 2 diabetes during the studies, and 12 percent of them had a normal weight when they got the diagnosis.
The death rate was 1.5 percent per year among overweight and obese people, compared to 2.8 percent per year among their trimmer peers.
For the study, scientists identified 2,625 men and women in the U.S. from five earlier studies who were over the age of 40 and had developed diabetes. The death rate among normal weight diabetes patients was 284.8 per 10,000 person-years, while the death rate for overweight or obese patients was 152.1 per 10,000 person-years.
After adjusting for demographics, blood pressure, waist circumference, smoking status and lipid levels, the researchers found that normal weight individuals were twice as likely to die from diabetes as overweight/obese people. They also found that older adults and non-white participants were more likely to develop normal-weight type 2 diabetes. "It was a little bit unexpected to see that," said Carnethon.
Dr. Hermes Florez, director of the division of epidemiology and population health sciences at the University of Miami’s Miller School of Medicine, suggested that, one possible explanation as to why normal weight people are at a higher risk may be due to fitness, that people who don’t maintain a healthy lifestyle might be putting themselves at risk for diseases, even if they are at a normal weight. "It’s not just the issue of fatness. It’s also the issue of fitness."
One potential limitation of the study is that the researchers couldn’t always account for how much people smoked, which might explain part of the results.
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. That could also have contributed to the findings, although Carnethon said the effect would be small.
She added that it’s not clear how to best treat normal-weight people with type 2 diabetes, although weight training seems preferable over cardio exercise.
Older people and people of Asian descent are more likely to be normal-weight when diagnosed with diabetes, and Carnethon stressed that doctors need to take the disorder especially seriously when it’s not accompanied by obesity.
"These findings do apply to a growing segment of the population," she said.
- The study also found an increased risk for cardiovascular mortality and more than a twofold greater risk for noncardiovascular mortality when comparing normal-weight patients with overweight or obese diabetics.
- Normal-weight adults with newly diagnosed type 2 diabetes had a significantly greater mortality risk compared with their overweight or obese counterparts.
Journal of the American Medical Association, online August 7, 2012.