The study, published in the Journal of the American Medical Association, also found that normal-weight people diagnosed with type 2 diabetes have double the risk of dying of heart disease and other causes than overweight people with diabetes.
First author Mercedes R. Carnethon of the Northwestern University Feinberg School of Medicine and colleagues said normal-weight adults with type 2 diabetes have been understudied because those who typically develop the disease were overweight or obese.
Carnethon and colleagues analyzed data from five studies and identified 2,625 U.S. men and women age 40 and older who were determined to have diabetes at the start of the studies, while some were diagnosed through their participation in the studies.
In this study, about 10 percent of those with new-onset diabetes were at a normal weight at the time of diagnosed.
"It could be that this is a very unique subset of the population who are at a particularly high risk for mortality and diabetes, and it is possible that genetics is a factor with these individuals," Carnethon said in a statement.