Resting and activity energy expenditure during total parenteral nutrition in rats with methylcholanthrene-induced sarcoma.

Tumor weight, carcass weight, nitrogen balance, energy balance, resting energy expenditure (REE), and activity energy expenditure (AEE) were measured in normal Fischer 344 rats, free-feeding Fischer 344 rats with methylcholanthrene-induced sarcoma (TB-FF), and similar tumor-bearing rats supported with total parenteral nutrition (TB-TPN). TB-FF rats became hypophagic and demonstrated weight loss, negative nitrogen balance, and negative energy balance as the tumor enlarged. TB-FF rats had a normal FEE and AEE when tumors were small and a decreased REE and AEE when tumors were large. TB-TPN rats were maintained in positive nitrogen and energy balance. TB-TPN rats had significantly increased REE throughout the study and a decreased AEE at the end of the study. Both the host carcass and the tumor responded to increased nutritional substrate with increased growth. The decline in motor activity which characterizes cancer cachexia may not be totally dependent on malnutrition.