Afternoon exercise linked to greatest HbA1c reduction in type 2 diabetes
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Key takeaways:
- Adults with obesity plus type 2 diabetes had the largest HbA1c reduction when they exercised during the afternoon.
- Afternoon exercise was linked to higher odds for discontinuing glucose-lowering medication.
Physical activity performed in the afternoon could yield a greater reduction in HbA1c than physical activity during other times in the day, according to an analysis of data from the Look AHEAD trial published in Diabetes Care.
“This is the first large-scale epidemiological study demonstrating that timing of unsupervised physical activity is associated with long-term improvement in blood glucose in type 2 diabetes,” Jingyi Qian, PhD, associate physiologist at Brigham and Women’s Hospital and instructor of medicine at Harvard Medical School, and Roeland J.W. Middelbeek, MD, MSc, assistant investigator and staff physician at the Joslin Diabetes Center and assistant professor of medicine at Harvard Medical School, told Healio. “Our findings highlight the potential of incorporating timing into physical activity interventions. While any amount of physical activity appears beneficial, the timing of the activity is linked to effects on blood glucose management.”
Qian, Middelbeek and colleagues obtained data from 2,331 adults aged 45 to 76 years with type 2 diabetes and overweight or obesity who participated in Look AHEAD and had accelerometry data available at year 1 and year 4 (mean age at baseline, 59.2 years; 57% women; 72% white). An accelerometer was used to measure the number of moderate to vigorous physical activity sessions, physical activity duration and timing. Participants were assigned timing groups based on when they conducted physical activity. For year 1, morning time was defined as 5 to 10:42 a.m., midday included exercise from 10:43 a.m. to 1:42 p.m., afternoon consisted of exercise from 1:43 to 5 p.m. and evening included exercise performed from 5 p.m. to midnight. For year 4, the times shifted to 5 to 10:30 a.m. for the morning, 10:31 a.m. to 1:18 p.m. for midday, 1:19 to 4:36 p.m. for the afternoon and 4:37 p.m. to midnight for the evening. Participants who exercised at varying times were placed into a mixed group. Demographics and anthropometric factors were collected at baseline and annual follow-ups. Change in HbA1c was assessed from baseline to year 1 and from year 1 to year 4.
There were 1,755 adults with accelerometry data available at year 1 and 2,047 with data available at year 4. Half of the study cohort was randomly assigned to lifestyle intervention in the trial. Adults who exercised in the morning at year 1 and who exercised at mixed times in year 4 had the highest amount and intensity of physical activity measured.
From baseline to year 1, HbA1c changes varied across time groups. Adults exercising in the afternoon had a larger decrease in HbA1c from baseline to year 1 when compared with inactive adults (mean difference, –0.22%; 95% CI, –0.39 to –0.06). There was no difference in HbA1c change between adults in the other exercise groups and inactive adults. No difference in HbA1c from year 1 to year 4 was observed for any of the exercise timing groups.
Among 1,939 adults who did not use insulin, exercising in the afternoon during year 1 was associated with a greater likelihood for discontinuing glucose-lowering medication compared with no physical activity (OR = 2.13; 95% CI, 1.29-3.52).
“Why afternoon exercise is better for patients with type 2 diabetes remains to be investigated,” Qian and Middelbeek said. “Some common hypotheses are, the circadian system regulates many physiological functions in our body, which may play a role in the time-specific benefits of physical activity. Other behavioral factors, such as fasting/postprandial states and sleep-wake cycles may also contribute to the glucose-lowering effect of physical activity. For example, post-meal physical activity, which may be occurring most often after lunch in the afternoon group, is an effective strategy for managing postprandial glucose excursions in type 2 diabetes.”
Qian and Middelbeek said the research team plans to test out the findings experimentally to investigate the underlying mechanisms that may explain the association between afternoon physical activity and glycemic control.
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