Body composition, sleeping metabolic rate (SMR), 24-h energy expenditure (24-EE) and daily physical activity were determined in 12 obese women during and after 12 weeks of exercise (4 h per week on 55 per cent of VO2 max) and/or energy restriction (2.9-3.5 MJ/d). Diet(D) and diet-exercise (DE) groups were formed by matching the subjects on their body mass index (BMI, kg/m2; mean 30.3). After 12 weeks no significant differences were shown in loss of weight (D 12.2 and DE 13.2 kg) and loss of fat mass (D 9.4 and DE 10.9 kg). Both groups reduced their SMR (D 29.9 per cent and DE 21.7 per cent) and their metabolic rate during the entire night measured by indirect calorimetry (12-EE) (D 36.4 per cent and DE 28.6 per cent; P less than 0.05). Energy expenditure over 24 h, estimated by means of heart-rate monitoring, was reduced by 22.1 per cent for D and by 19.6 per cent for DE (n.s.). Daily physical activity, which was determined during 5 d using an actometer, was increased after 12 weeks for DE (27 per cent; P less than 0.05) and D (10 per cent; n.s.). The suggestion that a reduction in normal activities of daily life in a diet-exercise group is the explanation for the absence of significant differences in weight and fat loss between a diet-exercise and a diet group is not confirmed in this study. Daily physical activity showed a significantly higher increase for the diet-exercise group than for the diet group, while the decline of SMR and 24-EE tended to be smaller.