[Lipolysis and lipid oxidation of weight stable patients with malignant tumors of the digestive system].

Tumor-caused weight loss is frequently associated with a high rate of lipolysis and fat oxidation. In order to differentiate the effect of weight-loss from the tumour-dependent regulation of fat metabolism, we studied weight-stable and well nourished patients (ideal body weight 109 +/- 4% (+/- SEM), body mass index 25.1 +/- 0.9 kg/m2). Parameters of lipolysis (glycerol-, fatty acid concentrations) and the calorimetric determined fat oxidation rate of five male tumor patients were examined before and during an euglycaemic insulinclamp (0.2 mU insulin/kg/min). Concomitant with a high rate of lipolysis (glycerol concentration 112 +/- 20 mumol/l, free fatty acid concentration 0.72 +/- 0.13 mmol/l) and fat oxidation (60% of energy expenditure) there was a low normal insulin level (5.9 +/- 0.5 mU/l). Insulin reduced lipolysis and fat oxidation and stimulated glucose oxidation. Weight-stable tumor patients have a high basal rate of lipolysis and fat oxidation; yet the insulin dependent regulation of the fat metabolism is intact, as we have already shown for weight-losing cancer patients.