“Physical exercise combined with diet restriction has been proven to be effective in prevention of diabetes. However, the long-term effect of exercise on prevention of diabetes, and the difference of exercise intensity in prevention of diabetes have not been well studied,” said corresponding author Xiaoying Li, MD, of Zhongshan Hospital, Fudan University, Shanghai, in an interview.
In the research letter published in JAMA Internal Medicine, Dr. Li and colleagues analyzed the results of a study of 220 adults with central obesity and nonalcoholic fatty liver disease, but no incident diabetes, randomized to a 12-month program of vigorous exercise (73 patients), moderate aerobic exercise (73 patients) or no exercise (74 patients).
A total of 208 participants completed the 1-year intervention; of these, 195 and 178 remained to provide data at 2 years and 10 years, respectively. The mean age of the participants was 53.9 years, 32.3% were male, and the mean waist circumference was 96.1 cm at baseline.
The cumulative incidence of type 2 diabetes in the vigorous exercise, moderate exercise, and nonexercise groups was 2.1 per 100 person-years 1.9 per 100 person-years, and 4.1 per 100 person-years, respectively, over the 10-year follow-up period. This translated to a reduction in type 2 diabetes risk of 49% in the vigorous exercise group and 53% in the moderate exercise group compared with the nonexercise group.
In addition, individuals in the vigorous and moderate exercise groups significantly reduced their HbA1c and waist circumference compared with the nonexercisers. Levels of plasma fasting glucose and weight regain were lower in both exercise groups compared with nonexercisers, but these differences were not significant.
The exercise intervention was described in a 2016 study, which was also published in JAMA Internal Medicine. That study’s purpose was to compare the effects of exercise on patients with nonalcoholic fatty liver disease. Participants were coached and supervised for their exercise programs. The program for the vigorous group involved jogging for 150 minutes per week at 65%-80% of maximum heart rate for 6 months and brisk walking 150 minutes per week at 45%-55% of maximum heart rate for another 6 months. The program for the moderate exercise group involved brisk walking 150 minutes per week for 12 months.
Both exercise groups showed a trend towards higher levels of leisure time physical activity after 10 years compared with the nonexercise groups, although the difference was not significant.
The main limitation of the study was that incident prediabetes was not prespecified, which may have led to some confounding, the researchers noted. In addition, the participants were highly supervised for a 12-month program only. However, the results support the long-term value of physical exercise as a method of obesity management and to delay progression to type 2 diabetes in obese individuals, they said. Vigorous and moderate aerobic exercise programs could be implemented for this patient population, they concluded.
“Surprisingly, our findings demonstrated that a 12-month vigorous aerobic exercise or moderate aerobic exercise could significantly reduce the risk of incident diabetes by 50% over the 10-year follow-up,” Dr. Li said in an interview. The results suggest that physical exercise for some period of time can produce a long-term beneficial effect in prevention of type 2 diabetes, he said.
Potential barriers to the routine use of an exercise intervention in patients with obesity include the unwillingness of this population to engage in vigorous exercise, and the potential for musculoskeletal injury, said Dr. Li. In these cases, obese patients should be encouraged to pursue moderate exercise, Dr. Li said.
Looking ahead, more research is needed to examine the potential mechanism behind the effect of exercise on diabetes prevention, said Dr. Li.