The purpose of this study was to investigate the effect of glucose infusion on lipid metabolism after abdominal surgery. Patients (n = 6) with non-metastasized colorectal carcinoma were investigated on the second day after surgery and healthy volunteers were studied after an overnight fast. The rates of glycerol appearance (R(a) glycerol), i.e., lipolysis rates, were assessed by primed continuous infusion of [1,1,2,3,3,-5H2]glycerol before and after 3 h of glucose infusion (4 mg x kg(-1) x min(-1)). Plasma concentrations of glycerol, free fatty acids, glucose, lactate, insulin, and glucagon were determined. Fasting R(a) glycerol was higher in patients than in volunteers (7.7 +/- 1.8 versus 1.9 +/- 0.3 micromol x kg(-1) x min(-1), P < 0.05). Glucose infusion suppressed the R(a) glycerol in volunteers to 1.0 +/- 0.2 micromol x kg(-1) x min(-1) (P < 0.05), whereas lipolysis was not affected in patients. Plasma concentrations of glycerol and free fatty acids similarly decreased during glucose administration by 50% in both groups (P < 0.05). In contrast to the patients, a significant correlation (r = 0.78, P < 0.05) between the R(a) glycerol and plasma glycerol concentration was observed in normal subjects. The hyperglycemic response to glucose infusion was significantly more pronounced (P < 0.05) in patients (10.7 +/- 0.7 mmol/L) than in volunteers (7.1 +/- 0.4 mmol/L), whereas the plasma insulin increased to the same extent in the two groups (P < 0.001). In conclusion, lipolysis rates are increased after abdominal surgery and glucose administration, most likely due to insulin resistance, and fail to inhibit stimulated whole-body lipolysis.