Some Obese People Don't Risk Heart Disease, Diabetes; Some Normal-Weight People Do
The finding comes from a study of risk factors for diabetes and heart disease in 5,440 obese, overweight, and normal-weight U.S. adults by Albert Einstein College researchers Rachel P. Wildman, PhD, Judith Wylie-Rosett, EdD, and colleagues.
"We used to think all fat did was store energy," Wylie-Rosett tells WebMD. "Now we know that fat tissue is hormone-producing tissue. It may act differently in different people."
Clues to what's going on come from a second study looking at 314 German adults with traditional risk factors for type 2 diabetes and heart disease: a family history of type 2 diabetes, obesity, or a personal history of high blood sugar or gestational diabetes.
Close examination revealed a wide range of true diabetes/heart disease risk factors. For normal-weight and overweight people, risk was linked to belly fat. But for obese people, risk wasn't so much linked to belly fat as it was to having a fatty liver.
Belly fat signals fat accumulation around the organs of the body. Bodies that don't get much exercise tend to grow this kind of fat.
Similarly, obese people who get at least moderate physical exercise tend to have less fatty livers than those who don't exercise. Fortunately, there's a lot a person can do about this, says study researcher Norbert Stefan, MD, of the University of Tubingen, Germany.
"The higher an obese person's activity level, the larger the decrease in liver fat," Stefan tells WebMD.
"It may be the fat-and-fit phenomenon," Wylie-Rosett agrees. "In our study, the obese people with better risk profiles tended to have more physical activity. And the normal-weight people with worse risk factors tended to have characteristics associated with lower physical activity levels."
Warning: Whether or not you're obese, being fit doesn't mean being without risk. It's all a matter of probability, says Lewis Landsberg, MD, director of the Northwestern University obesity center.
"For any particular disease, there are many people with risk factors that do not get the disease, and many people without risk factors who do," Landsberg tells WebMD. "We've known for a long time that although obesity is a risk factor for heart disease, many obese people don't have that risk. But across the population, those with more body fat will have an increased incidence of heart disease. And those with the apple-shaped, upper-body obesity are at greater risk than those with the pear-shaped, lower-body obesity."