High-intensity interval training is not superior to continuous aerobic training in reducing body fat: A systematic review and meta-analysis of randomized clinical trials

BACKGROUND/OBJECTIVE: Guidelines on obesity management reinforce regular exercise to reduce body fat. Exercise modalities, including high-intensity interval training (HIIT), appear to produce a similar effect to continuous aerobic training (CAT) on body fat. However, they have not addressed the chronic effect of HIIT vs. CAT on body fat assessed by dual energy X-ray absorptiometry (DEXA). Thus, we compared the effectiveness of CAT vs. HIIT protocols on body fat (absolute or relative) (%BF) and abdominal visceral fat reduction, assessed by DEXA, in adults with overweight and obesity. METHODS: We conducted a systematic review and meta-analysis of randomized clinical trials (RCTs) including both female or male adults with excess body weight. We performed searches in the databases MEDLINE (PubMed), EMBASE, Scopus, LILACS, Web of Science and Cochrane. RESULTS: In our analysis (11 RCTs), we found no greater benefit on %BF of HIIT vs. CAT (MD –0.55%, 95% CI –1.42 to 0.31; p = 0.209). As for abdominal visceral fat, no training modality was superior (SMD: −0.05, 95% CI –0.29 to 0.19; p = 0.997). Regarding secondary outcomes (body weight, BMI, VO(2) max, glycemic and lipid profiles), HIIT shows greater benefit than CAT in increasing VO(2) max and fasting blood glucose and reducing total cholesterol. CONCLUSION: HIIT is not superior to CAT in reducing %BF or abdominal visceral fat in individuals characterized by excess weight. However, HIIT showed beneficial effects on cardiorespiratory fitness, total cholesterol and fasting blood glucose when compared to CAT.