I found an interesting statistic in a scientific journal article last year:
Every 2.2 pound (1 kg) loss of excess weight lowers the risk of developing type 2 diabetes by 16%.
That tidbit was embedded in another article with a focus on regain of lost weight over time. The “16% per kilogram” number sounded too good to be true, and I had never heard it before. So I did some digging and found the source of the statistic. Ain’t the Internet wunnerful?
The origin of the 16% figure is the Diabetes Prevention Program Research Group. Investigators enrolled 1,079 middle-aged (mean 50.6 years) study participants and followed them over 3 years, noting the effects of exercise, percentage of fat in the diet, and weight loss on the subsequent development of diabetes. Average body mass index was 33.9. (A 5-foor, 4-inch person weighing 197 pounds (89.5 kg) has a BMI of 33.9). Sixty-eight percent of participants were women. The investigators’ goal for this group of overweight people was for loss of 7% of body weight through diet, physical activity, and periodic counseling sessions. Average weight loss over the course of three years was 9 pounds (4.1 kg).
None of the study participants had diabetes at the time of enrollment. But, by design, they all had laboratory-proven “impaired glucose tolerance.” Impaired glucose tolerance is a form of “pre-diabetes.” It is determined by giving a 75-gram dose of glucose by mouth, then measuring blood glucose (sugar) 2 hours later. A blood glucose level under 140 is normal. If the level is 140-199, you have impaired glucose tolerance.
Having impaired glucose tolerance means that study participants’ glucose (sugar) metabolism was already abnormal. They were at higher than average risk of developing diabetes, compared with both average-weight healthy people and overweight people without impaired glucose tolerance. This is a great cohort to study for development of diabetes. But the finding that “every 2.2 pounds of weight loss lowers the risk of diabetes by 16%” applies to this particular group with impaired glucose tolerance, not the general overweight population.
A total of 153 participants developed diabetes over the course of 3 years. Loss of excess weight was by far the best predictor of lowered diabetes risk, compared with regular exercise and lowering percentage of dietary fat.
Yes, weight loss does prevent diabetes in some, probably many, overweight people. The specific degree of reduced risk depends on numerous factors, such as age, sex, genetics, degree of weight loss, and pre-existing impaired glucose tolerance.
Steve Parker, M.D.