The Release of Lipolytic Hormones during Various High-Intensity Interval and Moderate-Intensity Continuous Training Regimens and Their Effects on Fat Loss.

To investigate the release of lipolytic hormones during various high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT), and their effects on fat loss. 39 young women categorized as obese (with a body fat percentage (BFP) ≥30%) were randomly allocated to one of the following groups: all-out sprint interval training (SIT, n =10); supramaximal HIIT (HIIT₁₂₀, 120%V̇O_2peak, n = 10); HIIT (HIIT₉₀, 90%V̇O_2peak, n = 10), or MICT, (60%V̇O_2peak, n = 9) for a twelve-week observation period consisting of 3 to 4 exercise sessions per week. Serum epinephrine (EPI) and growth hormone (GH) were measured during the 1st, 20th, and 44th training sessions. Body weight (BW), body mass index (BMI), whole-body fat mass (FM) and BFP were assessed pre- and post-intervention. Following the 1st and 20th sessions, significant increases in EPI (p < 0.05) were observed post-exercise in HIIT₁₂₀ and HIIT₉₀, but not in SIT and MICT. In the 44th session, the increased EPI was found in SIT, HIIT₁₂₀, and HIIT₉₀, but not in MICT (p < 0.05). For the GH, a significant increase was observed post-exercise in all groups in the three sessions. The increased EPI and GH returned to baselines 3 hours post-exercise. After the 12-week intervention, significant reductions in FM and BFP were found in all groups, while reductions in BW and BMI were only found in the SIT and HIIT groups. Greater reductions in FM and BFP, in comparison to MICT, were observed in the SIT and HIIT groups (p < 0.05). 12-week SIT, HIIT₁₂₀, and HIIT₉₀, in comparison to MICT, were more efficacious in fat reduction in obese women, partly benefiting from the greater release of lipolytic hormones during training sessions.