High-intensity Interval Training Vs. Moderate-intensity Continuous Training For Body Composition. A Systematic Review And Meta-analysis.

Physical activity is an important component of weight management, but the optimal exercise characteristics for body fat loss and weight reduction are not clear. High-intensity interval training (HIIT) is becoming increasingly popular as an alternative to moderate-intensity continuous training (MICT), with robust evidence for its efficacy to improve maximal aerobic fitness and vascular function in healthy and clinical populations. However, there are no systematic reviews exploring the relative merits of HIIT and MICT on body composition outcomes. PURPOSE: To conduct a systematic review and meta-analysis comparing the effects of HIIT and MICT protocols on body composition outcomes in overweight or obese, healthy adults. METHODS: Data was systematically sourced from controlled trials (randomised or matched) found on electronic search engines (MEDLINE, Scopus, Embase, SportDiscus, Web of Science, CINAHL and PEDro) up to September 2016. Trials directly compared HIIT and MICT intervention in healthy but overweight or obese patients aged 18-45 years. Outcome measures included body mass, body fat, lean mass and trunk fat. Data was analysed using RevMan 5.3 and SPSS. RESULTS: From 1330 articles, 15 studies were included, involving 455 participants (mean age = 33years; BMI = 29.6; 53% male). HIIT (N=231) and MICT (N=224) interventions duration averaged nearly 11 weeks (3.5 sessions/week), and the majority of studies applied matched exercise modes and work outputs. Weekly exercise time was significantly lower in HIIT than MICT (95.5 vs. 158.54 minutes; p = 0.002). Both HIIT and MICT appear to induce modest improvements (effect sizes ranging 0.2-0.3) in body mass, BMI, body fat % and fat mass (kg), and waist circumference. There was no significant difference in effectiveness of HIIT and MICT on any of these outcome measures, with no significant heterogeneity in any of the 32 analyses conducted. CONCLUSION: Exercise training involving either HIIT or MICT can induce mild improvements in body composition. HIIT is just as efficacious as MICT for improving body composition, however HIIT requires ~40% less time commitment. More studies are required to analyse regional-specific changes in body fat, especially central adiposity and visceral fat.