Food-related gastrointestinal symptoms are common in irritable bowel syndrome (IBS), but the mechanisms behind this are unclear. Enhanced colorectal sensitivity after duodenal lipid administration in IBS patients has been demonstrated. However, the effects of a regular meal on colorectal sensitivity in these patients and the importance of the composition of the meal are not known. On two separate days, 10 IBS patients and 11 controls randomly received a liquid meal (800 kcal), containing 60% calories from fat (fatty meal) or carbohydrate (carbohydrate meal). Using a barostat rectal sensitivity was assessed during four separate distension sequences before, immediately after and 30 and 60 min after the meal. In the patients, the discomfort (P = 0.04) and the pain thresholds (P = 0.007) were gradually reduced after the fatty meal, whereas only a tendency in the same direction was seen after the carbohydrate meal. In patients VAS ratings for pain increased after the fatty meal (P = 0.03), but not after carbohydrates. In the controls, sensory thresholds were not affected by the meals. In IBS, a liquid meal enhances rectal sensitivity, and this seems to be partly nutrient dependent as a fatty meal has more pronounced effects than a carbohydrate meal. This might be of relevance for their postprandial symptoms.