Effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on fat oxidation during exercise: a systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of controlled trials
PubMed 35859145 · doi:10.1136/bjsports-2021-105181
What was done
A systematic review and meta-analysis searched nine electronic databases (including PubMed/MEDLINE, Scopus, CINAHL, and Web of Science) for between-group studies evaluating the effects of high-intensity interval training (HIIT) or sprint interval training (SIT) on fat oxidation during exercise (FatOx) compared with no exercise or moderate-intensity continuous training (MICT). Eligible participants were adults who were not trained athletes.
What was found
Eighteen fair-to-good quality studies were included (9 comparing HIIT/SIT to no exercise; 11 comparing HIIT/SIT to MICT). HIIT and SIT significantly increased FatOx overall (mean difference [MD] = 0.08 g/min, 95% CI 0.04 to 0.12, p < 0.001). Significant benefits appeared at ≥4 weeks and increased with every additional week of training (β = 0.01, 95% CI 0.00 to 0.02, p = 0.003). HIIT/SIT was slightly more effective than MICT (MD = 0.03 g/min, 95% CI 0.01 to 0.05, p = 0.005), with larger effect sizes observed in adults with overweight or obesity.
Why it matters
This synthesis demonstrates that interval training regimens enhance exercise fat oxidation capacity more than standard moderate-intensity continuous training, with progressive improvements over longer training durations and pronounced benefits in individuals with overweight or obesity.
Limits
The absolute difference in fat oxidation rates was modest (0.08 g/min vs control, 0.03 g/min vs MICT). Total participant count and exact adherence metrics were not reported in the abstract. Trained athletes were excluded, restricting applicability to non-athletic adult populations.
Cited by
- partial Meta-analyses demonstrate that high-intensity interval training increases mitochondrial content and carnitine palmitoyltransferase enzyme levels and activity more than low- to moderate-intensity training.