Appetite: Natural recurring desire for food. Alterations may be induced by APPETITE DEPRESSANTS or APPETITE STIMULANTS.Appetite Regulation: Physiologic mechanisms which regulate or control the appetite and food intake.Appetite Depressants: Agents that are used to suppress appetite.Appetite Stimulants: Agents that are used to stimulate appetite. These drugs are frequently used to treat anorexia associated with cancer and AIDS.Satiation: Full gratification of a need or desire followed by a state of relative insensitivity to that particular need or desire.Hunger: The desire for FOOD generated by a sensation arising from the lack of food in the STOMACH.Satiety Response: Behavioral response associated with the achieving of gratification.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.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.Eating: The consumption of edible substances.Peptide YY: A 36-amino acid peptide produced by the L cells of the distal small intestine and colon. Peptide YY inhibits gastric and pancreatic secretion.Feeding Behavior: Behavioral responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals.Drinking: The consumption of liquids.Energy Intake: Total number of calories taken in daily whether ingested or by parenteral routes.Thirst: A drive stemming from a physiological need for WATER.Peptide Hormones: Hormones synthesized from amino acids. They are distinguished from INTERCELLULAR SIGNALING PEPTIDES AND PROTEINS in that their actions are systemic.Diethylpropion: A appetite depressant considered to produce less central nervous system disturbance than most drugs in this therapeutic category. It is also considered to be among the safest for patients with hypertension. (From AMA Drug Evaluations Annual, 1994, p2290)Leptin: A 16-kDa peptide hormone secreted from WHITE ADIPOCYTES. Leptin serves as a feedback signal from fat cells to the CENTRAL NERVOUS SYSTEM in regulation of food intake, energy balance, and fat storage.Meals: A portion of the food eaten for the day, usually at regular occasions during the day.Hypothalamus: Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.Fenfluramine: A centrally active drug that apparently both blocks serotonin uptake and provokes transport-mediated serotonin release.Gastrointestinal Hormones: HORMONES secreted by the gastrointestinal mucosa that affect the timing or the quality of secretion of digestive enzymes, and regulate the motor activity of the digestive system organs.Cholecystokinin: A peptide, of about 33 amino acids, secreted by the upper INTESTINAL MUCOSA and also found in the central nervous system. It causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. Cholecystokinin may be the mediator of satiety.Cross-Over Studies: Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)Glucagon-Like Peptide 1: A peptide of 36 or 37 amino acids that is derived from PROGLUCAGON and mainly produced by the INTESTINAL L CELLS. GLP-1(1-37 or 1-36) is further N-terminally truncated resulting in GLP-1(7-37) or GLP-1-(7-36) which can be amidated. These GLP-1 peptides are known to enhance glucose-dependent INSULIN release, suppress GLUCAGON release and gastric emptying, lower BLOOD GLUCOSE, and reduce food intake.Energy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Postprandial Period: The time frame after a meal or FOOD INTAKE.Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Obesity: A status with BODY WEIGHT that is grossly above the acceptable or desirable weight, usually due to accumulation of excess FATS in the body. The standards may vary with age, sex, genetic or cultural background. In the BODY MASS INDEX, a BMI greater than 30.0 kg/m2 is considered obese, and a BMI greater than 40.0 kg/m2 is considered morbidly obese (MORBID OBESITY).Food Preferences: The selection of one food over another.Cachexia: General ill health, malnutrition, and weight loss, usually associated with chronic disease.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)Neuropeptide Y: A 36-amino acid peptide present in many organs and in many sympathetic noradrenergic neurons. It has vasoconstrictor and natriuretic activity and regulates local blood flow, glandular secretion, and smooth muscle activity. The peptide also stimulates feeding and drinking behavior and influences secretion of pituitary hormones.Drinking Behavior: Behaviors associated with the ingesting of water and other liquids; includes rhythmic patterns of drinking (time intervals - onset and duration), frequency and satiety.Phentermine: A central nervous system stimulant and sympathomimetic with actions and uses similar to those of DEXTROAMPHETAMINE. It has been used most frequently in the treatment of obesity.Gastric Emptying: The evacuation of food from the stomach into the duodenum.Injections, Intraventricular: Injections into the cerebral ventricles.Agouti-Related Protein: A secreted protein of approximately 131 amino acids that is related to AGOUTI SIGNALING PROTEIN and is also an antagonist of MELANOCORTIN RECEPTOR activity. It is expressed primarily in the HYPOTHALAMUS and the ADRENAL GLAND. As a paracrine signaling molecule, AGRP is known to regulate food intake and body weight. Elevated AGRP has been associated with OBESITY.Taste: The ability to detect chemicals through gustatory receptors in the mouth, including those on the TONGUE; the PALATE; the PHARYNX; and the EPIGLOTTIS.Hyperphagia: Ingestion of a greater than optimal quantity of food.Sodium, Dietary: Sodium or sodium compounds used in foods or as a food. The most frequently used compounds are sodium chloride or sodium glutamate.Furosemide: A benzoic-sulfonamide-furan. It is a diuretic with fast onset and short duration that is used for EDEMA and chronic RENAL INSUFFICIENCY.Dexfenfluramine: The S-isomer of FENFLURAMINE. It is a serotonin agonist and is used as an anorectic. Unlike fenfluramine, it does not possess any catecholamine agonist activity.Pro-Opiomelanocortin: A 30-kDa protein synthesized primarily in the ANTERIOR PITUITARY GLAND and the HYPOTHALAMUS. It is also found in the skin and other peripheral tissues. Depending on species and tissues, POMC is cleaved by PROHORMONE CONVERTASES yielding various active peptides including ACTH; BETA-LIPOTROPIN; ENDORPHINS; MELANOCYTE-STIMULATING HORMONES; and others (GAMMA-LPH; CORTICOTROPIN-LIKE INTERMEDIATE LOBE PEPTIDE; N-terminal peptide of POMC or NPP).Food: Any substances taken in by the body that provide nourishment.Clinical Trials, Phase IV as Topic: Planned post-marketing studies of diagnostic, therapeutic, or prophylactic drugs, devices, or techniques that have been approved for general sale. These studies are often conducted to obtain additional data about the safety and efficacy of a product. This concept includes phase IV studies conducted in both the U.S. and in other countries.Weight Loss: Decrease in existing BODY WEIGHT.Blood Glucose: Glucose in blood.Weight Gain: Increase in BODY WEIGHT over existing weight.Receptor, Melanocortin, Type 4: A melanocortin receptor subtype found primarily in BRAIN. It shows specificity for ALPHA-MSH; BETA-MSH and ADRENOCORTICOTROPIC HORMONE.Dietary Carbohydrates: Carbohydrates present in food comprising digestible sugars and starches and indigestible cellulose and other dietary fibers. The former are the major source of energy. The sugars are in beet and cane sugar, fruits, honey, sweet corn, corn syrup, milk and milk products, etc.; the starches are in cereal grains, legumes (FABACEAE), tubers, etc. (From Claudio & Lagua, Nutrition and Diet Therapy Dictionary, 3d ed, p32, p277)Receptors, Ghrelin: Transmembrane proteins that recognize and bind GHRELIN, a potent stimulator of GROWTH HORMONE secretion and food intake in mammals. Ghrelin receptors are found in the pituitary and HYPOTHALAMUS. They belong to the family of G-PROTEIN-COUPLED RECEPTORS.Pylorus: The region of the STOMACH at the junction with the DUODENUM. It is marked by the thickening of circular muscle layers forming the pyloric sphincter to control the opening and closure of the lumen.Insulin: A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).Eating Disorders: A group of disorders characterized by physiological and psychological disturbances in appetite or food intake.Nutritional Status: State of the body in relation to the consumption and utilization of nutrients.