Increased physical activity is associated with increased energy expenditure and weight loss, given a stable energy intake. It has been hypothesized that exercise aimed to improve aerobic fitness (VO2max) may also increase energy expenditure at rest (RMR) and during exercise (EE). This has yet not reached scientific consensus.


A total of 82 patients with severe obesity attending Vestfold Hospital Trust were included in the present study. Patients were randomized to one of two semi-annual exercise programs for 24 weeks with different exercise intensity in the middle of the treatment period. The two different exercise modalities were moderate (MICT) or high intensity aerobic exercise (HAIT). Primary analyses were conducted “per protocol” and involved all patients who completed the prescribed intervention for six months (N = 40). Secondary analysis involved all patients who were randomly assigned to either HAIT or MICT (N = 37 and 34 respectively).


Per protocol, HAIT improved EE 1.4 Kcal·kg-75·h-1 and VO2max 5.3 mL·kg-0.75·min-1 more than MICT in the middle period (P= 0.003 and 0.004 respectively). Also, weight loss improved 2.1 kg more in HAIT than in MICT (P= 0.002) in this period. During the whole 24 weeks period, HAIT reached a 3.3 kg greater weight loss than MICT (P= 0.036). No significant differences between HAIT and MICT were found in the secondary analysis.


HAIT improved energy expenditure during exercise, aerobic fitness and weight loss more than MICT in the middle period. During the whole 24 weeks period, HAIT reached greater weight loss than MICT. HAIT seems to have a positive effect on energy expenditure and weight loss in patients with severe obesity.