Jingyi Qian, PhD
Jingyi Qian, Qian Xiao, Michael P. Walkup, Mace Coday, Melissa L. Erickson, Jessica Unick, John M. Jakicic, Kun Hu, Frank A.J.L. Scheer, Roeland J.W. Middelbeek, and the Look AHEAD Research Group
Research Category: Cardiovascular, Diabetes, and Metabolic Disorders
Background: We determined the longitudinal association of time-of-day of bout-related moderate-to-vigorous physical activity (bMVPA) with changes in glycemic control across 4 years in adults with type 2 diabetes in the Look AHEAD trial.
Methods: Among 2416 participants (57% female; mean age, 59 years) with 7-day waist-worn accelerometry recording at year 1 or 4, we defined the time-varying exposure by time-of-day of bMVPA: ≥50% of bMVPA during the same time period (Morning, Midday, Afternoon, or Evening), <50% of bMVPA in any time period (Mixed), and ≤1 day with bMVPA per week (Inactive, the reference).
Results: HbA1c reduction at year 1 varied by bMVPA timing (P=0.02), independent of bMVPA volume and intensity. The afternoon group had the greatest HbA1c reduction, the magnitude of which was 30%-50% larger than the other groups. The odds of discontinuation versus maintaining/initiating glucose-lowering medications at year 1 differed by bMVPA timing (P=0.04). The afternoon group had the highest odds (OR: 2.13 [1.29, 3.52]). For all the bMVPA timing groups, there were no significant changes in HbA1c between year 1 and 4.
Conclusions: bMVPA performed in the afternoon is associated with improvements in glycemic control in adults with diabetes, especially within the initial 12 months of an intervention.
Regular physical activity has been a cornerstone of lifestyle interventions for blood glucose management in diabetes. Here we revealed a significant association between timing of bout-related moderate-to-vigorous physical activity and improvements in glucose control among adults with overweight/obesity and type 2 diabetes. Participants who performed more physical activity in the afternoon had the greatest reduction in HbA1c as well as the highest odds for discontinuation of glucose-lowering medication, especially during the first year when the most intensive intervention occurred. The magnitude of HbA1c reduction in the afternoon group during year 1 was 30%-50% larger than all the other groups. Importantly, the association of timing of physical activity with changes in HbA1c was independent of the weekly physical activity volume and intensity. Future well-powered randomized control trials with long-term timed physical activity interventions are needed to establish causality, confirm these findings, and to develop evidence-based recommendations.