BACKGROUND: Aerobic exercise is recommended for weight management but energy balance is often less negative than predicted from exercise energy expenditure (ExEE).

OBJECTIVE: To examine effects of active commuting and leisure-time exercise on fat loss in women and men with overweight and obesity.

METHODS: We randomized 130 younger, physically inactive women and men with overweight and obesity (body mass index: 25-35 kg m-2) to 6 months of habitual lifestyle (control; CON, n=18), active commuting (BIKE, n=35) or leisure-time exercise of moderate (MOD, 50% VO2peak reserve, n=39) or vigorous intensity (VIG, 70% VO2peak reserve, n=38). The primary outcome was change in fat mass measured by dual-energy X-ray absorptiometry, which was analyzed intention-to-treat. Accumulated energy balance was calculated based on changes in body composition, and ExEE was calculated based on heart rate monitoring during exercise.

RESULTS: Testing at 3 and 6 months was completed by 95 and 90 participants, respectively. Fat mass was reduced after 3 and 6 months in BIKE (3 months: -3.6 (-5.5; -1.7) kg (mean (95% CI)); 6 months: -4.2 (-6.6; -1.9) kg; both: P<0.001), MOD (3 months: -2.2 (-3.9; -0.4) kg; 6 months: -2.6 (-4.8; -0.5) kg, both: P<0.02) and VIG (3 months: -3.4 (-5.2; -1.7) kg; 6 months: -4.5 (-6.6; -2.3) kg; both: P<0.001) compared with CON. Furthermore, fat loss was greater in VIG compared with MOD (6 months: -1.8 (-3.6; -0.1) kg, P=0.043). Based on the ExEE and the accumulated energy balance MOD compensated for the ExEE (77 (48; 106) %) but not BIKE (38 (-18; 95) %) and VIG (21 (-14; 55) %).

CONCLUSIONS: A meaningful fat loss was obtained by 6 months of active commuting and leisure-time exercise, but fat loss was greater with vigorous compared with moderate intensity exercise. Active commuting is an alternative to leisure-time exercise in the management of overweight and obesity. The trial was registered at clinicaltrials.gov as NCT01962259 (main trial) and NCT01973686 (energy metabolism sub-study).International Journal of Obesity advance online publication, 5 December 2017; doi:10.1038/ijo.2017.253.