The present invention relates to methods and nutritional compositions for the prevention and treatment of cachexia and anorexia. The methods of the invention comprise administering a composition comprising effective amounts of .omega.-3 fatty acids such as alpha-linolenic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid or mixtures thereof; of branched-chain amino acids valine, leucine, isoleucine or mixtures thereof; with or without reduced levels of tryptophan and 5-hydroxytryptophan; and of antioxidant system selected from the group comprising beta-carotene, vitamin C, vitamin E, selenium, or mixtures thereof.