Because resistant starch (RS) is not absorbed as glucose in the small intestine of healthy humans, postprandial thermogenesis should be lower after the intake of RS as compared with digestible starch. To evaluate this hypothesis, we measured 5-h postprandial thermogenesis and substrate oxidation by indirect calorimetry after ingestion of 50 g pregelatinized (0% RS) and 50 g raw potato starch (54% type II RS) in 15 healthy, normal-weight young males. The subjects consumed each starch (mixed in diluted fruit syrup) twice on separate days and in random order. RS intake was followed by lower thermogenesis (46.5 +/- 13.1 compared with 115.4 +/- 10.4 kJ/5 h; P = 0.008), lower glucose oxidation (P < 0.0005), and greater fat oxidation (P = 0.013) than was pregelatinized starch consumption. Our results suggest that RS has no thermogenic effect and that its presence does not influence the size of the thermic response to digestible starch.