Introduction: Obesity, and particularly visceral adiposity, is a significant contributor to lifetime risk of cardiovascular disease. Exercise training reduces visceral adipose tissue (VAT), however it remains unclear if exercise intensity influences the degree of fat reduction. The aim of this study was to compare isocaloric high intensity interval training (HIIT) and moderate intensity continuous training (MICT) on VAT and body composition.
Methods: 29 participants (26 male) with coronary artery disease (CAD) commencing a cardiac rehabilitation program (mean age 64±8years and body mass index of 27.8±3.5kg/m2) were randomised to 12-weeks of HIIT or MICT, 3 times per week. Estimated energy expenditure for the training was ~1MJ per session (3MJ per week). Both groups received standard cardiac rehabilitation nutrition education. VAT and abdominal subcutaneous fat (SAT) were measured by a 3 Telsa magnetic resonance imaging system. Transverse slice images from diaphragm to pelvis (L5/S1) were used to quantify total volumes by semi-automated specialised software. Total fat mass (FM) and fat free mass (FFM) were measured by dual energy x-ray absorptiometry. Data was analysed by ANOVA with baseline data used as a covariate.
Results: There was a significant (p<0.05) effect of time over 12 weeks on total VAT volume (HIIT: -348±287cm3 [-13%±13%], MICT: -501±495cm3 [-16%±14%]), total SAT volume (HIIT: -211±186cm3 [-6%±5%], MICT: -315±360cm3 [-9%±10%]), FM (HIIT: -1.0±1.3kg, MICT: -2.6±2.4kg), and FFM (HIIT: +0.3±0.9kg, MICT: +0.9±1.5kg), but only a significant group difference for FM favouring MICT (p=0.05). No significant differences for time (p=0.82) or group (p=0.69) were found for energy intake. MICT participants reported significantly greater average exercise minutes per week (HIIT: 144±51min, MICT: 259±131min, p=0.006).
Conclusion: Both HIIT and MICT provide a clinically significant reduction in VAT (13-16%) over 12 weeks in patients with CAD. HIIT may offer similar reduction in visceral adiposity with less time commitment.