Background Although a single bout of postmeal exercise can lower postprandial glucose (PPG), its optimal timing remains unclear. Objective This study aimed to investigate the effect of exercise timing using an individualized approach on PPG in overweight or obese young men. Methods Twenty men [age: 23.0 ± 4.3 y; BMI (kg/m2): 27.4 ± 2.8] each completed three 240-min trials in a randomized order separated by 6–14 d: 1) sitting (SIT), 2) walking initiated at each participant's PPG-peak time (PPGP) (iP), and 3) walking initiated 20 min before the PPGP (20iP). For each participant, PPGP was predetermined using continuous glucose monitoring. Walking was performed at 50% maximal oxygen consumption for 30 min. Venous blood was collected at 15- and 30-min intervals for 0–120 min and 120–240 min, respectively. The primary outcome was plasma PPG. Generalized estimating equations were used for comparison between trials. Results Compared with SIT, the 4-h incremental AUCs (iAUCs) for plasma PPG (−0.6 mmol · L−1 · h; P = 0.047) and insulin (−28.7%, P < 0.001) were reduced in 20iP only, and C-peptide concentrations were lower after iP (−14.9%, P = 0.001) and 20iP (−28.7%, P < 0.001). Plasma insulin (−11.1%, P = 0.006) and C-peptide (−8.3%, P = 0.012) were lower due to the 20iP compared with iP treatment. Finally, PPG reductions due to iP and 20iP occurred only in men with a BMI > 27.5 kg/m2 (iP, −11.2%; 20iP, −14.7%; P = 0.047) and higher glucose iAUC values during SIT (iP, −25.5%; 20iP, −25.7%; P < 0.001). Conclusions Walking initiated 20 min before PPGP lowered PPG and plasma insulin and C-peptide concentrations in young men with overweight or obesity, in particular in those with high BMI or glucose iAUC values during SIT; it also lowered plasma insulin and C-peptide concentrations more effectively than did exercise initiated at PPGP. This trial was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx) as ChiCTR1900023175.

Background Postprandial dysmetabolism, an important cardiovascular disease risk factor, can be improved by exercise. Further systematic review and meta-analysis is needed to compare the effects of accumulated exercise with a single session of energy-matched continuous exercise on postprandial glucose (PPG), insulin, and triglycerides in adults with or without diabetes. Methods Eight electronic databases were searched on August 28, 2020, and updated on April 27, 2021. Eligible studies were randomized, quasi-randomized, or non-randomized controlled or crossover trials that evaluated the acute or longitudinal effects of accumulated exercise compared with a single session of energy-matched continuous exercise on PPG, postprandial insulin, and triglycerides in diabetic and non-diabetic adults. Same-day and second-morning effects were assessed separately for acute intervention studies. Subgroup analyses were conducted based on the number of exercise bouts (2–3 bouts or frequent brief bouts (e.g., 1–6 min) throughout the day at 20–60-min intervals (known as physical activity [PA] breaks, ≥ 5 bouts)), exercise intensity, and populations. Risk of bias was assessed using the revised Cochrane risk-of-bias tool for randomized trials. Pooled effects were reported as standardized mean differences (SMD) and 95% CI using a random effects model. Results Twenty-seven studies (635 participants) were included. A significant difference was found for same-day PPG control, which favored accumulated exercise over one bout of energy-matched continuous exercise (SMD − 0.36 [95%CI: (− 0.56, − 0.17)], P = 0.0002, I2 = 1%), specifically in accumulated exercise with PA breaks (SMD − 0.36 [95%CI: (− 0.64, − 0.08)], P = 0.01, I2 = 30%), low-moderate intensity exercise (SMD − 0.38 [(95%CI: (− 0.59, − 0.17)], P = 0.0005, I2 = 0%), and in non-diabetic populations (SMD − 0.36 [95%CI: (− 0.62, − 0.10)], P = 0.007, I2 = 16%). No differences were found for same-day postprandial insulin and triglycerides, and second-morning effects (postprandial or fasting glucose, insulin, and triglycerides) between different exercise patterns. Conclusion Compared with one session of continuous exercise, accumulated exercise—specifically in subgroups of PA breaks, low-moderate intensity exercises—produced greater acute effects on same-day PPG control for non-diabetic adults. There were no differences between continuous and accumulated patterns of exercise in terms of same-day postprandial insulin and triglycerides, and second-morning effects on all previously mentioned markers. The findings provide additional PA options for PPG control for individuals with limited time or exercise capacity to engage in PA in one session. Registration: PROSPERO (identification code: CRD42021251325).

Context Prolonged sitting elevates postprandial metabolic markers, resulting in increased risks of cardiovascular diseases and type-2 diabetes. Interrupting prolonged sitting may reduce these risks. However, more information is needed to understand the patterns of interrupting prolonged sitting to obtain metabolic health benefits. Objective The study examined the effects of interrupting prolonged periods of sitting with different intensities and durations of walking with an equivalent energy expenditure on postprandial metabolic responses in young Chinese men with central obesity. Design Randomized crossover experimental trial. Setting Participants underwent three 6-h experiments with a 7-day washout period between each experiment: prolonged sitting (SIT), 3 min of light-intensity walking every 30 min (3 min), and 1.5 min of moderate-intensity walking every 30 min (1.5 min). Participants and Samples Baseline (fasting) and 6-h postprandial metabolic glucose and lipid levels were analyzed among 18 young Chinese men with central obesity. Main Outcome Measures Generalized estimating equations (adjusted for the potential confounders explaining residual outcome variance (body mass index (BMI) and age), trial order, preprandial values, and lead-in activity) were used, and the incremental areas under the curve (iAUC) of each outcome were compared between prolonged sitting and interrupted prolonged sitting conditions. Results Compared with SIT, both interrupting prolonged sitting conditions reduced the iAUCs for glucose (p < 0.05) but not insulin, C-peptide, triglycerides, or nonesterified fatty acids. Conclusions Both conditions of interrupted prolonged sitting reduced postprandial glucose concentrations in young Chinese men with central obesity when the energy expenditure was equivalent.