Effects of exercise snacks on cardiorespiratory fitness, body composition, and blood lipids in adults across different age groups: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the effects of exercise snacks on cardiorespiratory fitness, body composition, and blood lipids among adults of different age groups. METHODS: PubMed, Web of Science, CINAHL, Embase, the Cochrane Library, and Scopus were searched from inception to April 15, 2026. Randomized controlled trials evaluating exercise snacks in adults were included. Two reviewers independently performed study selection, data extraction, and risk-of-bias assessment. Subgroup analyses, meta-regression, sensitivity analyses, and publication bias assessments were conducted. RESULTS: Twenty-one studies involving 921 participants were included. Exercise snacks significantly improved maximal oxygen uptake (VO2max; g = 1.04, 95% CI = 0.68-1.39; moderate-certainty evidence) and peak power output (PPO; g = 0.68, 95% CI = 0.25-1.10; moderate-certainty evidence), whereas body fat percentage showed an overall increase (g = 0.51, 95% CI = 0.01-1.02; low-certainty evidence). No statistically significant effects were observed for total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, or triglycerides. VO2max improved in studies with mean participant ages <25 and 25-50 years, but not >50 years, whereas PPO improved across all three age strata. Further analyses suggested that a greater number of exercise bouts per day, an intervention frequency of 4-5 days per week, and an intervention duration of 7-9 weeks may be associated with greater improvements in cardiorespiratory fitness. CONCLUSION: Exercise snacks may improve cardiorespiratory fitness in adults, although effects may vary by age and intervention characteristics. Evidence for body composition and blood lipids remains inconsistent, and the age-based findings require confirmation using individual participant data.