Obesity Paradox: Thin Not in for Type 2 Diabetes?
Normal Weight in People Diagnosed With Type 2 Diabetes Tied to Higher Risk of Early Death
Body Composition, Fat Distribution May Trump Body Size in Diabetes
One is body composition -- the ratio of fat to muscle. Muscle is critical to controlling blood sugar because it is metabolically active, uses insulin, and burns sugars and calories.
"The muscle-versus-fat ratio is extremely important for diabetes development as well as health outcomes related to diabetes," Carnethon says.
Studies show that it's becoming more common for normal-weight people to carry less muscle and more body fat.
Doctors have even coined a term for this: TOFI, or thin outside, fat inside. It's especially common in older adults who naturally lose muscle and bone with age.
"It could well be that these people do have an adverse body fat distribution. They haven't measured it in this study, so you can't be 100% sure, but it would fit into the general idea that these people have an adverse fat distribution. There could be more on the inside," says E. Louise Thomas, PhD, a research scientist at University College London. Thomas studies body fat and metabolism, but she was not involved in the research.
"What may be very significant is not just the actual weight, but what's in that weight. What's the ratio between muscle and fat and where is that fat stored?" says Rifka C. Schulman, MD, an endocrinologist at Long Island Jewish Medical Center in New Hyde Park, N.Y.
Normal-weight people may also get a different kind of diabetes than people who are overweight. Whatever the reason, experts say the study should be a wake-up call to clinicians that normal-weight people with diabetes need close attention.
"I think normal-weight people get overlooked to a certain extent because traditionally, that hasn't been where the problem is," Thomas says.