Afternoon exercise linked to greater improvements in blood sugar levels for patients with type 2 diabetes

More than 37 million Americans have diabetes, and 90 to 95% of that population are diagnosed with type 2 diabetes. Lifestyle interventions, such as a healthy diet and a regular physical activity program, are methods of managing diabetes.

A new study from a collaboration of researchers at Brigham and Women’s Hospital, a founding member of the Mass General Brigham health system, and the Joslin Diabetes Center, part of Beth Israel Lahey Health, uses data from the Look AHEAD (Action for Health in Diabetes) study , a randomized controlled trial that compared an intensive lifestyle intervention with diabetes support and education in patients diagnosed with type 2 diabetes and overweight or obesity to track the development of cardiovascular disease over time.

In the current study, the research team assessed whether physical activity at certain times of the day was associated with greater improvement in blood glucose control. Their findings suggest that patients with type 2 diabetes who were physically active in the afternoon had the greatest improvements after one year in the study. The team’s results are published in diabetes care .

“In this study, we showed that adults with type 2 diabetes had the greatest improvement in glucose control when they were most active in the afternoon,” said co-author Jingyi Qian, Ph.D., of the Division of Sleep and Circadian Disorders at Brigham . “We knew that physical activity is beneficial, but what our study adds is a new understanding that timing of activity may also be important.”

Doctors recommend that patients with diabetes participate in regular physical activity as a method to control their blood glucose levels. Elevated blood glucose levels can put people with type 2 diabetes at risk for heart disease, visual impairment and kidney disease.

The team analyzed physical activity data from the first and fourth years of the Look AHEAD study, which included data from more than 2,400 participants. During the study, participants wore a waist accelerometry recording device to measure physical activity.

When Brigham and Joslin’s team reviewed the first-year data, they determined that those who engaged in moderate-to-vigorous physical activity in the afternoon had the greatest reduction in blood glucose levels. When comparing data from the fourth year, the afternoon group maintained the reduction in blood glucose. In addition, the afternoon group also had the highest chance of discontinuing their glucose-lowering/diabetes medications.

Brigham and Joslin’s team notes that their investigation has limitations; for example, their study is observational and does not measure confounders such as sleep and food intake.

In future studies, the team may test their findings experimentally to investigate underlying mechanisms that may explain why the time of day of activity can influence blood glucose control. From there, the team can provide specific physical activity recommendations for patients.

“Time seems to matter,” said co-author Roeland Middelbeek, MD, assistant investigator at the Joslin Diabetes Center. “In the future, we may have more data and experimental evidence for patients to provide more personalized recommendations.”