Whole body lipid and energy metabolism in the cancer patient.

The relationship between whole-body energy and lipid kinetics in eight cancer patients was investigated after an overnight fast. Respiratory gas exchange and indirect calorimetry were used to obtain resting energy expenditure (REE) and net substrate oxidation rates. Free fatty acid (FFA) turnover, oxidation, and clearance rates were obtained after a primed-constant infusion of albumin bound 1-14C-Na palmitate. This was followed by a primed-constant, two-stage infusion of unlabeled glycerol to measure plasma glycerol turnover and clearance. The REE was 1.3 times the predicted (by the Harris-Benedict equation) basal energy expenditure. FFA and glycerol, plasma concentrations, and turnover rates were higher in these depleted but hypermetabolic cancer patients, compared to reported values for healthy normals. The ratio of FFA turnover to glycerol turnover was 3.14 +/- 0.38, which is close to the theoretical value of 3, suggesting complete hydrolysis of triglycerides and the absence of any extensive reesterification of FFA in adipose tissue. The net fat oxidation accounts for 53 +/- 5% of fat mobilized and 29 +/- 3% of the FFA turnover was converted to CO2 in the process of supplying energy in cancer patients. The results suggest that fat is efficiently mobilized and utilized as a fuel source in hypermetabolic cancer patients in the postabsorptive state.