Among the overall type 2 diabetic population, only about one-eighth are of normal weight; most are overweight or obese. In the current report a meta-analysis of five previous studies over 2,500 diabetics were assessed. The patients were tracked over intervals ranging from nine to 28 years. At the time of diagnosis, patients were classified as either normal weight (BMI between 18.5 and 24.9) or overweight/obese (BMI of 25 or greater).
The results showed that, among people classified as normal weight at diagnosis, the annual death rate was about 285 per 10,000 people. This rate was nearly double that found for obese and overweight diabetics: 152 deaths per 10,000.
The researchers, led by Dr. Mercedes Carnethon of Northwestern University s Feinberg School of Medicine, found that heart disease mortality rates did not significantly vary between the two groups. However, they could not account for the increased death rate in normal weight diabetics a failure due possibly their retrospective meta-analysis method, which makes specific factors impossible to determine.
The study doesn t give any clues as to why normal weight diabetics are dying at a higher rate," says ACSH's Dr. Gilbert Ross. "The authors did take into account factors such as age, blood pressure, blood fat levels, waist circumference, and smoking status. Yet because this is a meta-analysis of past studies, it s more difficult to track down the exact causes of death although they did state that the difference was not due to heart disease. The lack of other information is very frustrating.
One limitation to the study is that the researchers used BMI alone to distinguish between obese and normal-weight diabetics. As ACSH s Dr. Ruth Kava points out, BMI is not a perfect reflection of body composition, or of fat distribution and metabolism. She continues, It s likely that there is a different etiology affecting normal weight diabetics that contributes to these findings.