Exercise Snacks and Acute Postprandial Glucose and Insulin Metabolism: An Umbrella Review and De Novo Meta-Analysis

Background/Objectives: Exercise snacks-brief, purposeful bouts of physical activity distributed throughout the day-may modify postprandial metabolic regulation, particularly glucose handling and insulin responses, while reducing time barriers to structured exercise. However, repeated primary studies and variable definitions may overstate evidence maturity. We reappraised evidence on exercise snacks and acute postprandial metabolism using review-level evaluation and independent study families. Methods: We conducted an umbrella review with de novo meta-analyses when evidence was sufficiently comparable. Six bibliographic databases and three supplementary literature-discovery sources were searched through 5 August 2026. Exercise snacks were defined as active bouts ≤ 15 min, performed at least twice per intervention day, and distributed across the day. AMSTAR 2, ROBIS, and corrected covered area (CCA) assessed review quality, risk of bias, and overlap. Random-effects models used restricted maximum likelihood with Hartung-Knapp adjustment; paired crossover effects were Hedges' g_z. RoB 2 and GRADE were applied. Results: Twenty-one systematic reviews were included; outcome-specific CCA ranged from 11.2% to 30.2%. After deduplication, only four study families contributed to acute plasma glucose iAUC, three to plasma insulin iAUC, and two to exploratory acute CGM glucose iAUC. Given these small evidence sets and the conservative Hartung-Knapp adjustment, the analyses had limited precision and statistical power to detect small-to-moderate effects. No statistically clear pooled effect was observed for plasma glucose (Hedges' g_z = -0.127, 95% CI -1.111 to 0.857; I² = 77.9%) or insulin iAUC (Hedges' g_z = -0.520, 95% CI -1.263 to 0.222; I² = 15.3%). The two-study CGM synthesis was descriptive and hypothesis-generating and neither supported nor refuted an acute glucose effect. Conclusions: Review-level abundance exceeded the independent quantitative evidence available for robust inference. The current analyses were underpowered to establish small-to-moderate pooled effects of exercise snacks on acute postprandial glucose or insulin metabolism; therefore, the findings indicate limited and statistically unstable evidence rather than evidence of no metabolic benefit.