The Impact Of Exercise Timing On Glycemic Control In Type 2 Diabetes And Overweight/obesity

PURPOSE: Exercise timing is perceived as a contemporary hot topic, especially in the field of type 2 diabetes mellitus (T2DM) where glucose homeostasis undergoes daily circadian rhythms. However, the impact of exercise at different times of the day remains to be fully explored in people with T2DM. This investigation examines the effects of exercise at different periods of the day (morning period (MP), afternoon period (AP), and evening period (EP)) on glucose regulation in patients with T2DM and in a matched control group. METHODS: Patients with T2DM (n = 8) and a matched control group with overweight/obesity (n = 8) underwent a randomized crossover trial, which included three 2-week blocks of supervised post-prandial exercise (i.e., MP, AP, and EP) using high-intensity interval training (HIIT) (6 sessions each block). A 2-week washout period was included between each training block. 22-h continuous glucose monitoring (CGM) was assessed in both groups before and after each exercise block. Meals were standardized across conditions for all participants. Within- and between-group changes on mean glucose and total area under the curve (AUCtotal) were modeled using generalized linear mixed-models. RESULTS: After adjusting for sex, age, and treatment order, there was no significant between-group changes on CGM AUCtotal (MP*AP: β = -0.52, p = 0.957; MP*EP: β = 0.83, p = 0.928; EP*AP: β = -1.35, p = 0.886) and mean glucose (MP*AP: β = -2.96, p = 0.768; MP*EP: β = -2.76, p = 0.775; EP*AP: β = -0.20, p = 0.984) for the T2DM group. Similar results were observed for the matched control group for the CGM AUCtotal (MP*AP: β = -4.31, p = 0.436; MP*EP: β = -0.24, p = 0.966; EP*AP: β = -4.07, p = 0.462) and mean glucose (MP*AP: β = -5.60, p = 0.274; MP*EP: β = -2.91, p = 0.575; EP*AP: β = -2.68, p = 0.600). When looking at within group changes, a favorable time effect (p < 0.05) was observed only for the T2DM group on the AUCtotal for the morning (Δ-14.35, CI: -28.21, -0.49) and afternoon period (Δ-13.29, CI: -26.01, -0.59). CONCLUSIONS: Our findings suggest that there are no differences in glycemic benefits associated with exercise at a specific time of the day in both T2DM and overweight/obese individuals. Future studies on the long-term effects of exercise timing are warranted, to better understand the influence of daily circadian rhythms on glycemic control. Supported by: This study was funded by the Fundação para a Ciência e Tecnologia (2022.08130. PTDC). The funder has no role in the study in terms of the design, data collection, management, analysis, and interpretation.