Afternoon physical activity linked to greater HbA1c reduction than other times of day
A secondary analysis of the Look AHEAD (Action for Health in Diabetes) study found that participants who performed more moderate to vigorous physical activity in the afternoon versus other times of day had the greatest reduction in HbA1c compared to those who were inactive.
Afternoon physical activity was associated with better blood glucose control in a retrospective study of patients with type 2 diabetes.
The Look AHEAD (Action for Health in Diabetes) study enrolled 5,145 participants ages 45 to 76 years with overweight/obesity and type 2 diabetes and randomly assigned them to a four-year lifestyle intervention, in which the most intensive intervention occurred in the first year, or a control treatment. Of these, 2,627 participants were enrolled in a substudy to assess physical activity using waist-mounted accelerometry. The current study examined the longitudinal associations of participants' timing of unsupervised bouts of moderate to vigorous physical activity (bMVPA) assessed at year 1 and year 4 with changes in glycemic measures and use of glucose-lowering medications over four years.
The researchers assigned 1,755 and 2,047 participants to groups based on temporal distribution of bMVPA. They defined the time-varying exposure of bMVPA (10-minute bout or longer) as 50% or more of bMVPA occurring during the same time period (morning, midday, afternoon, or evening), less than 50% of bMVPA in any time period (mixed), and one or fewer days with bMVPA per week (inactive). The primary outcome was change in HbA1c from the previous assessment (i.e., from baseline to year 1 and from year 1 to year 4). Results were published May 25 by Diabetes Care.
HbA1c reduction at year 1 varied across the timing groups (P=0.02), independent of treatment arm, weekly bMVPA volume and intensity, and body mass index. Compared with the inactive group, the afternoon group had the greatest HbA1c reduction from baseline to year 1 (−0.22%; 95% CI, −0.39% to −0.06%). Specifically, the least squared means of decrease in HbA1c in the afternoon group was about 50% larger than the decrease in the mixed group at year 1 (−0.89% [95% CI, −1.34% to −0.44%] vs. −0.60% [95% CI, −1.04% to −0.16%]), with an adjusted difference in HbA1c of −0.20% to −0.29% compared with all other groups. There were no significant changes in HbA1c between year 1 and year 4 for all the bMVPA timing groups. In addition, the likelihood of stopping versus maintaining or starting glucose-lowering medications at year 1 differed by bMVPA timing (P=0.04), with the afternoon group having the highest odds (odds ratio, 2.13; 95% CI, 1.29 to 3.52).
Data on sleep, dietary intake, and meal timing were unavailable, the study authors noted. They added that participants who performed most bMVPA in the afternoon might have had better underlying health or health behaviors to facilitate glucose management, among other limitations.
“Further research with in-depth information on sleep patterns and nutrient intake is needed to better delineate the relationships between timing of bMVPA and glycemic control in type 2 diabetes,” the authors wrote. “Our findings, together with others, highlight an exciting interdisciplinary research frontier on lifestyle interventions and circadian biology, which holds promise for optimizing treatment efficacy.”