Effect Of Diurnal Exercise Timing On Postprandial Glucose Responses: A Randomized Controlled Trial

Abstract

PURPOSE: Postprandial exercise has been shown to reduce postprandial glucose (PPG) response to a greater degree than preprandial exercise, suggesting an important yet under-acknowledged role for exercise timing on glycemic control. Whether diurnal timing of exercise imparts additional benefits on PPG responses remains unclear. This study aimed to determine the diurnal effect of exercise timing on PPG response in individuals enrolled into a 12-week supervised multi-modal exercise training program. METHODS: Forty sedentary overweight individuals (17 males, 23 female; age: 51 ± 13 years; BMI: 30.9 ± 4.2 kg/m2) with (n = 20) or without T2DM diagnosis were randomly allocated to either a morning (amEX) or evening (pmEX) exercise training group. All participants completed the 12-week supervised multi-modal exercise training program (3 days per week), which consisted of 30 minutes of aerobic exercise (walking protocol) and 4 resistance-based exercises (3 sets of 12-18 repetitions). The amEX and pmEX training sessions occurred in the postprandial state between 0700-0900h and 1700-1900h, respectively. Changes in postprandial glucose (PPG) and insulin (PPI) responses, during a mixed meal tolerance test (MMTT) were the primary outcome measures of the study assessed at baseline and post-intervention at 12 weeks. All data is displayed as mean differences ± SD. RESULTS: Exercise training reduced (main effect of time, p < 0.01) PPG and PPI concentrations during the MMTT, with no group differences observed (p = 0.69). A significantly greater reduction in PPG-iAUC was observed for the pmEX group (-78.56 mmol/L) when compared to the amEX group (-33.22 mmol/L) at post-intervention (p = 0.03). Reductions in PPI iAUC (main effect of time, p < 0.01) were observed at post-intervention, with no group differences reported (p = 0.18) CONCLUSIONS: Irrespective of the diurnal timing of exercise performance, 12-weeks of multi-modal exercise training significant improved PPG and PPI responses in both overweight non-T2DM and T2DM individuals.