A 12-month program of moderate to vigorous exercise reduced the risk of type 2 diabetes by approximately 50% in adults with obesity over 10 years, according to a new analysis of a study.
"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.
Findings fill gap in long-term outcome data
The current study is important because of the long-term follow-up data, said Jill Kanaley, PhD, professor and interim chair of nutrition and exercise physiology at the University of Missouri, in an interview. "We seldom follow up on our training studies, thus it is important to see if there is any long-term impact of these interventions," she said.
Dr. Kanaley said she was surprised to see the residual benefits of the exercise intervention 10 years later.
"We often wonder how long the impact of the exercise training will stay with someone so that they continue to exercise and watch their weight; this study seems to indicate that there is an educational component that stays with them," she said.
The main clinical takeaway from the current study was the minimal weight gain over time, Dr. Kanaley said.
Although time may be a barrier to the routine use of an exercise intervention, patients have to realize that they can usually find the time, especially given the multiple benefits, said Dr. Kanaley. "The exercise interventions provide more benefits than just weight control and glucose levels," she said.
"The 30-60 minutes of exercise does not have to come all at the same time," Dr. Kanaley noted. "It could be three 15-minute bouts of exercise/physical activity to get their 45 minutes in," she noted. Exercise does not have to be heavy vigorous exercise, even walking is beneficial, she said. For people who complain of boredom with an exercise routine, Dr. Kanaley encourages mixing it up, with activities such as different exercise classes, running, or walking on a different day of any given week.
Although the current study was conducted in China, the findings may translate to a U.S. population, Dr. Kanaley said in an interview. However, "frequently our Western diet is less healthy than the traditional Chinese diet. This may have provided an immeasurable benefit to these subjects," although study participants did not make specific adjustments to their diets, she said.
Additional research is needed to confirm the findings, said Dr. Kanaley. "Ideally, the study should be repeated in a population with a Western diet," she noted.
Next steps for research include maintenance of activity
Evidence on the long-term benefits of exercise programs is limited, said Amanda Paluch, PhD, a physical activity epidemiologist at the University of Massachusetts, Amherst, in an interview.
"Chronic diseases such as diabetes can take years to develop, so understanding these important health outcomes requires years of follow-up. This study followed their study participants for 10 years, which gives us a nice glimpse of the long-term benefits of exercise training on diabetes prevention," she said.
Data from previous observational studies of individuals' current activity levels (without an intervention) suggest that adults who are more physically active have a lower risk of diabetes over time, said Dr. Paluch. However, the current study is one of the few with rigorous exercise interventions with extensive follow-up on diabetes risk, and it provides important evidence that a 12-month structured exercise program in inactive adults with obesity can result in meaningful long-term health benefits by lowering the risk of diabetes, she said.
"The individuals in the current study participated in a structured exercise program where their exercise sessions were supervised and coached," Dr. Paluch noted. "Having a personalized coach may not be within the budget or time constraints for many people," she said. Her message to clinicians for their patients: "When looking to start an exercise routine, identify an activity you enjoy and find feasible to fit into your existing life and schedule," she said.
"Although this study was conducted in China, the results are meaningful for the U.S. population, as we would expect the physiological benefit of exercise to be consistent across various populations," Dr. Paluch said. "However, there are certainly differences across countries at the individual level to the larger community-wide level that may influence a person's ability to maintain physical activity and prevent diabetes, so replicating similar studies in other countries, including the U.S., would be of value."
"Additionally, we need more research on how to encourage maintenance of physical activity in the long-term, after the initial exercise program is over," she said.
"From this current study, we cannot tease out whether diabetes risk is reduced because of the 12-month exercise intervention or the benefit is from maintaining physical activity regularly over the 10 years of follow-up, or a combination of the two," said Dr. Paluch. Future studies should consider teasing out participants who were only active during the exercise intervention, then ceased being active vs. participants who continued with vigorous activity long-term, she said.
The study was supported by the National Nature Science Foundation, the National Key Research and Development Program of China, and the Shanghai Municipal Science and Technology Major Project. The researchers, Dr. Kanaley, and Dr. Paluch had no financial conflicts to disclose.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
Lead image: Nattaphon Moontichai/Dreamstime
© 2023 Frontline Medical Communications Inc.
Cite this: Exercise Halves T2D Risk in Adults With Obesity - Medscape - Feb 02, 2023.