Intraduodenal infusions of both lipid and glucose modulate gastrointestinal motility, stimulate plasma cholecystokinin (CCK) and peptide YY (PYY), and suppress appetite and energy intake, with lipid being more potent than glucose, while only glucose raises blood glucose and stimulates insulin. We hypothesized that increasing the ratio of maltodextrin, a complex carbohydrate, relative to lipid would be associated with a reduction in effects on antropyloroduodenal pressures, gut hormones, appetite and energy intake, when compared with lipid alone. Ten healthy males were studied on three occasions in double-blind, randomized order. Antropyloroduodenal pressures, plasma CCK, PYY and insulin, blood glucose and appetite were measured during 90-min intraduodenal infusions of (i) 3 kcal/min lipid ("L3"), (ii) 2 kcal/min lipid and 1 kcal/min maltodextrin ("L2/CHO1") or (iii) 1 kcal/min lipid and 2 kcal/min maltodextrin ("L1/CHO2"). Energy intake at a buffet lunch consumed immediately after the infusion was quantified. Reducing the lipid (thus, increasing the carbohydrate) content of the infusion was associated with reduced stimulation of basal pyloric pressures (r = 0.76, P < 0.01), plasma CCK (r = 0.66, P < 0.01) and PYY (r = 0.98, P < 0.001) and reduced suppression of antral (r = -0.64, P < 0.05) and duodenal (r = -0.69, P < 0.05) pressure waves, desire-to-eat (r = -0.8, P < 0.001) and energy intake (r = 0.74, P < 0.01), with no differences in phasic (isolated) pyloric pressures. In conclusion, in healthy males, intraduodenal lipid is a more potent modulator of gut function, associated with greater suppression of energy intake, when compared with isocaloric combinations of lipid and maltodextrin.