Many patients with cancer suffer anorexia and unintentional weight loss. Suprisingly, the development of cancer associated cachexia can even occur in patients with very small tumors and forced enteral and parenteral feedings have often failed to completely reverse the metabolic changes which lead to loss of lean tissue. Similarities exist between the metabolic response to injury and those occurring with active tumor growth. Both conditions are associated with loss of body weight and lean tissue, especially from skeletal muscle, increased leucine oxidation, and accelerated rates of gluconeogenesis. In the post-traumatic patient, complete diets fortified with additional branched chain amino acids have been shown to improve nitrogen retention and support protein synthesis more effectively than standard crystalline amino acid patterns. It is the goal of this application to determine the efficacy of branched chain amino acid enriched parenteral formulas to better support host tissue and reduce or postpone the development of cancer associated cachexia. The efficacy of such solutions will be determined by dynamic and static measurements of protein and glucose metabolism, including tumor growth, protein content and synthetic rate, carcass nitrogen analysis, whole body leucine and glucose turnover, energy expenditure, and fractional protein synthesis rates of muscle, liver and albumin. The information gained should provide further insight into the mechanisms behind the development of cancer associated cachexia and evaluate whether branched chain amino acid enriched diets have a role in the treatment of cancer cachexia.