Short-term effects of low-fat (10% fat energy), mixed (30% fat energy), and high-fat (50% fat energy) diets on 24-h energy expenditure, and on its components sleeping metabolic rate, diet induced thermogenesis and energy expenditure for physical activity were studied for 3 days using a respiration chamber in twelve normal-weight female volunteers classified as restrained or unrestrained eaters. There were no significant differences in any of the four measures between the restrained and unrestrained eating subjects on any of the diets. Within the group of restrained eaters, 24-h energy expenditure was significantly decreased during consumption of the mixed diet (8.21 +/- 0.21 MJ/d; p < 0.01) and tended to be decreased on the high-fat diet (8.22 +/- 0.25 MJ/d; p = 0.055), relative to the low-fat diet (8.58 +/- 0.21 MJ/d). Diet composition had no effect on 24-h energy expenditure in the women with unrestrained eating. The results suggest that a low-fat diet would be beneficial in the treatment of obesity, especially if subjects have a restrained type of eating behaviour.