Effect of Low-Volume Interval Training on Whole-Body, Abdominal and Visceral Fat in Adults Living with Overweight and Obesity: A Systematic Review and Meta-analysis

Abstract Background Interval training can be classified into high-intensity interval training (HIIT, 80%-100%V̇O 2max ) and sprint interval training (SIT, ≥ 100%V̇O 2max ) according to exercise intensity. HIIT can be further divided into high-volume HIIT (HV-HIIT, pure training time ≥ 15min/session) and low-volume HIIT (LV-HIIT, pure training time < 15min/session). The effectiveness of HV-HIIT in reducing body fat among adults has been well-proven, but there is a lack of comprehensive analysis on the impacts of low-volume interval training (i.e. LV-HIIT and SIT) on fat loss. Objective The systematic review and meta-analysis aim to determine the effectiveness of low-volume interval training in improving whole-body fat, abdominal and visceral fat in adults living with overweight and obesity. Methods Following the PRISMA guidelines and inclusion criteria, eligible articles were extracted from seven electronic databases and the reference lists of key papers in the field. The search was limited to English articles published on and before May 2023. Effect sizes were calculated as standardized mean difference (SMD) for four intervention outcomes, whole-body fat, body fat percentage, abdominal fat, and visceral fat. Results Out of the 4568 identified studies, a total of 50 randomized controlled trials were included, involving 1843 participants (age: 19.8 to 70.5 years, BMI: 25 to 39.5 kg/m 2 ). The low-volume interval training protocol included in this review had an average training duration of 9.5 weeks, a frequency of 3.3 times per week, an exercise session time of 6.2 minutes, and an exercise intensity of ≥ 80%V̇O 2max or HR max . Compared to the comparator groups of no-exercising (CON), low-volume interval training significantly reduced whole-body fat mass (-6.4%, p < 0.001), body fat percentage (-5.3%, p < 0.001), abdominal fat (-5.8%, p = 0.02) and visceral fat (-12.6%, p < 0.001). Compared to moderate-intensity continuous training (MICT), low-volume interval training showed a significant reduction in visceral fat (-3.9%, p = 0.04). No significant differences were observed between low-volume interval training and HV-HIIT in four outcome measures. Conclusion Low-volume interval training (LV-HIIT and SIT) groups show significant reductions in whole-body, abdominal and visceral fat among overweight and obese adults. It is more effective than MICT in reducing visceral fat. These findings emphasize the efficiency of low-volume interval training as an intervention for fat loss. The study protocol was registered (Registration No.: CRD42022341699) with the International Prospective Register of Systematic Reviews (PROSPERO).