Chronic high-intensity interval training and moderate-intensity continuous training are both effective in increasing maximum fat oxidation during exercise in overweight and obese adults: A meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of controlled intervention trials
PubMed 37701124 · doi:10.1016/j.jesf.2023.08.001
What was done
A systematic review and meta-analysis evaluating the chronic effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on maximal fat oxidation (MFO) in overweight and obese adults. Studies with a between-group design were included, and subgroup, meta-regression, and sensitivity analyses were performed.
What was found
Thirteen studies of moderate to high quality encompassing 519 participants (HIIT n = 136, MICT n = 235, Control n = 148) were analyzed: - HIIT vs. no-training control: statistically significant increase in MFO (MD = 0.07; 95% CI [0.03, 0.11]; I² = 0%). - MICT vs. no-training control: statistically significant increase in MFO (MD = 0.10; 95% CI [0.06, 0.15]; I² = 95%). - HIIT vs. MICT direct comparison: no significant difference in MFO change (MD = 0.01; 95% CI [-0.02, 0.04]; I² = 64%). - Exercise intensity (Fatmax vs. non-Fatmax; %VO2peak), exercise mode, BMI, and baseline VO2peak significantly moderated the effect of MICT on MFO. - No evidence of publication bias was identified (Egger's test p > 0.05 for all analyses).
Why it matters
Both interval and continuous aerobic training improve capacity for fat oxidation during exercise in overweight and obese adults to a similar extent, allowing flexibility in exercise selection.
Limits
Statistical heterogeneity was extremely high for MICT analyses (I² = 95%) and substantial for head-to-head comparisons (I² = 64%). Total participant numbers were relatively small across 13 trials, with only 136 in HIIT arms. High protocol diversity across HIIT studies prevented the determination of specific optimal training parameters.
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