Plasma (a) PYY and (b) CCK concentrations during fasting and duodenal nutrient stimulation in feed-tolerant (n = 9) and feed-intolerant (n = 10) critically ill patients. Feed-tolerant patients: open diamond, solid line; feed-intolerant patients: closed square, solid line. Both fasting and nutrient-stimulated PYY and CCK concentrations were higher in patients with feed intolerance compared with feed-tolerant patients. *P < 0.05, **P < 0.001 versus feed-tolerant patients. CCK, cholecystokinin; PYY, peptide YY.