Sex Differences In Postprandial Glucose Responses To Active Breaks To Sitting In Adults With Overweight/obesity

Reductions in postprandial glycemia following acute breaks to sitting are more pronounced in females than males. It is unclear whether these greater benefits are sustained over time and what are the mechanistic underpinnings. PURPOSE: To compare the effects of breaking up sedentary behavior (SB) with brisk walking on postprandial glucose and insulin responses, 24-h carbohydrate (CHO) oxidation, and skeletal muscle mitochondrial CHO oxidation in female vs males. METHODS: 15 sedentary adults with overweight/obesity (8F, 35 ± 8 y, 31.3 ± 4.3 kg/m2; 7 M, 32 ± 8 y, 28.4 ± 3.7 kg/m2) performed a 1-month intervention aimed at breaking up SB with 9 hourly 5-min bouts of brisk walking (45 min/d), 5 d/wk. Daily pattern of PA/SB was assessed with ActiGraph GT3X and ActivPAL for 14 d before and over the last 2 wks of intervention. At Pre and Post, participants underwent a 23-h study visit. Plasma glucose and insulin were assessed in fasting state, every hour for 13 h and following morning, and incremental area under the curve (iAUC) was calculated. Total CHO oxidation was measured by whole-room calorimetry. Mitochondrial respiration in presence of CHO-like substrates was measured by high resolution respirometry in permeabilized muscle fibers. Sex-by-time interaction for dependent variables was tested using linear mixed effect models. RESULTS: There were no changes in total time spent sedentary (p = .274). Both sexes reduced time spent in prolonged sitting (>60 min; p = .014) and increased time spent in moderate-to-vigorous PA (p = .010). After PA intervention, glucose iAUC significantly decreased in females compared to males (p = .012). Coupled respiration normalized for maximal oxidative capacity increased more in females than in males (p = .044). No sex-by-time interactions were observed for insulin iAUC, 24-h CHO oxidation, and other mitochondrial respiratory states (all p > .050). CONCLUSIONS: Females with overweight/obesity had a more pronounced reduction in postprandial glucose responses along with greater muscle mitochondrial CHO-like substrate respiration compared to males after a 1-month intervention aimed at breaking up SB with brisk walking. Because hyperglycemia is a risk factor for type 2 diabetes and its cardiovascular complications, breaking up SB can be potential strategy for type 2 diabetes prevention in females.