The claimEvidence A · guideline-tier
Spot reduction (sit-ups burn belly fat)
The evidence
Vispute 2011 + Kostek 2007: local training doesn't shift regional fat loss; lipolysis is hormone-driven, system-wide.
The mechanism, in brief
HIIT (High-Intensity Interval Training) = short bouts of high-intensity work (≥85% maxHR) alternated with short low-intensity recovery, repeated in cycles.
Sources (3)
- Milanović, Z., Sporiš, G., & Weston, M. (2015). Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: A systematic review and meta-analysis of controlled trials. Sports Medicine, 45(10), 1469-1481. HIIT ≈ continuous moderate-intensity for VO2max, at ~30% the training time.
- Gibala, M. J., Little, J. P., MacDonald, M. J., & Hawley, J. A. (2012). Physiological adaptations to low-volume, high-intensity interval training in health and disease. The Journal of Physiology, 590(5), 1077-1084. Mechanistic review of HIIT-induced mitochondrial and cardiovascular adaptations.
- Achten, J., & Jeukendrup, A. E. (2003). Maximal fat oxidation during exercise in trained men. International Journal of Sports Medicine, 24(8), 603-608. Max fat-oxidation occurs around 59-64% VO2max; above that the absolute fat-oxidation rate falls even as relative % rises — the empirical basis for debunking the 'fat-burning zone' marketing.