The effects of HIIT and MICT on body fat composition and cardiopulmonary fitness in adults: a meta-analysis of randomized controlled trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 41580784 · doi:10.1186/s13102-025-01519-2
What was done
A systematic review and meta-analysis of randomized controlled trials searched PubMed, Embase, Cochrane Library, and Web of Science to evaluate the differential effects of HIIT cycling versus moderate-intensity continuous training (MICT) on body fat composition and cardiorespiratory fitness in adults. Pooled standardized mean differences (SMD) were calculated using Review Manager 5.4 and Stata 18, with heterogeneity evaluated using the I² statistic and subgroup analyses stratified by population (disease, obese, sedentary).
What was found
Nineteen RCTs were included. Compared to MICT: - BMI in obese populations: HIIT significantly reduced BMI (SMD = -0.59 kg/m², 95% CI: -0.84 to -0.34, P < 0.001). - BMI in disease populations: HIIT was associated with a slight increase in BMI (SMD = 0.40 kg/m², 95% CI: 0.03 to 0.77, P = 0.042). - VO₂peak in obese populations: HIIT yielded greater improvements than MICT (SMD = 0.23 ml·kg⁻¹·min⁻¹, 95% CI: 0.01 to 0.45, P = 0.041). - VO₂peak in sedentary populations: HIIT yielded substantially greater improvements than MICT (SMD = 6.21 ml·kg⁻¹·min⁻¹, 95% CI: 4.68 to 7.74, P < 0.001). - Body composition: HIIT and MICT showed comparable efficacy for body fat percentage, fat mass, and lean body mass.
Why it matters
This review supports HIIT cycling as a time-efficient alternative to continuous exercise that confers superior cardiorespiratory fitness gains in sedentary and obese adults, with equivalent outcomes for overall body fat and lean mass.
Limits
The abstract restricts analysis to cycling protocols and does not report total participant counts, intervention durations, adverse events, or dietary controls. Effect size estimates labeled as SMDs are reported with physical units (kg/m² and ml·kg⁻¹·min⁻¹), suggesting potential reporting inconsistencies in the abstract, and numerical results for non-BMI body composition measures are omitted.
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