Cachexia: General ill health, malnutrition, and weight loss, usually associated with chronic disease.Anorexia: The lack or loss of APPETITE accompanied by an aversion to food and the inability to eat. It is the defining characteristic of the disorder ANOREXIA NERVOSA.Appetite Stimulants: Agents that are used to stimulate appetite. These drugs are frequently used to treat anorexia associated with cancer and AIDS.Wasting Syndrome: A condition of involuntary weight loss of greater then 10% of baseline body weight. It is characterized by atrophy of muscles and depletion of lean body mass. Wasting is a sign of MALNUTRITION as a result of inadequate dietary intake, malabsorption, or hypermetabolism.Muscular Atrophy: Derangement in size and number of muscle fibers occurring with aging, reduction in blood supply, or following immobilization, prolonged weightlessness, malnutrition, and particularly in denervation.Megestrol Acetate: Megestrol acetate is a progestogen with actions and uses similar to those of the progestogens in general. It also has anti-androgenic properties. It is given by mouth in the palliative treatment or as an adjunct to other therapy in endometrial carcinoma and in breast cancer. Megestrol acetate has been approved to treat anorexia and cachexia. (From Reynolds JEF(Ed): Martindale: The Extra Pharmacopoeia (electronic version). Micromedex, Inc, Englewood, CO, 1995)Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Weight Loss: Decrease in existing BODY WEIGHT.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Neoplasms: New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms.Receptor, Melanocortin, Type 4: A melanocortin receptor subtype found primarily in BRAIN. It shows specificity for ALPHA-MSH; BETA-MSH and ADRENOCORTICOTROPIC HORMONE.Ghrelin: A 28-amino acid, acylated, orexigenic peptide that is a ligand for GROWTH HORMONE SECRETAGOGUE RECEPTORS. Ghrelin is widely expressed but primarily in the stomach in the adults. Ghrelin acts centrally to stimulate growth hormone secretion and food intake, and peripherally to regulate energy homeostasis. Its large precursor protein, known as appetite-regulating hormone or motilin-related peptide, contains ghrelin and obestatin.Nutritional Support: The administration of nutrients for assimilation and utilization by a patient by means other than normal eating. It does not include FLUID THERAPY which normalizes body fluids to restore WATER-ELECTROLYTE BALANCE.Interleukin-6: A cytokine that stimulates the growth and differentiation of B-LYMPHOCYTES and is also a growth factor for HYBRIDOMAS and plasmacytomas. It is produced by many different cells including T-LYMPHOCYTES; MONOCYTES; and FIBROBLASTS.Eating: The consumption of edible substances.Melanocortins: Peptides derived from pro-opiomelanocortin (POMC) which can stimulate MELANOCYTES or CORTICOTROPHS. Melanocortins include ACTH; ALPHA-MSH; and other peptides such as BETA-MSH and GAMMA-MSH, derived from other fragments of POMC. These peptides act through a variety of MELANOCORTIN RECEPTORS to control different functions including steroidogenesis, energy homeostasis, feeding, and skin pigmentation.Neoplasms, Experimental: Experimentally induced new abnormal growth of TISSUES in animals to provide models for studying human neoplasms.