Hyperphagia: Ingestion of a greater than optimal quantity of food.Eating: The consumption of edible substances.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.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.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.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).Prader-Willi Syndrome: An autosomal dominant disorder caused by deletion of the proximal long arm of the paternal chromosome 15 (15q11-q13) or by inheritance of both of the pair of chromosomes 15 from the mother (UNIPARENTAL DISOMY) which are imprinted (GENETIC IMPRINTING) and hence silenced. Clinical manifestations include MENTAL RETARDATION; MUSCULAR HYPOTONIA; HYPERPHAGIA; OBESITY; short stature; HYPOGONADISM; STRABISMUS; and HYPERSOMNOLENCE. (Menkes, Textbook of Child Neurology, 5th ed, p229)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.Arcuate Nucleus: A nucleus located in the middle hypothalamus in the most ventral part of the third ventricle near the entrance of the infundibular recess. Its small cells are in close contact with the ependyma.Feeding Behavior: Behavioral responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals.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).Body Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.Energy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Kleine-Levin Syndrome: A rare condition characterized by recurrent hypersomnias associated with hyperphagia, occurring primarily in males in the second to third decade of life. Clinical features include mental confusion, excessive sleep requirements (approximately 18 hours per day), restlessness, and in some cases hallucinations. Episodes have a duration of days to weeks, and may recur several times per year. This condition may resolve spontaneously over several years. (From Adams, et al., Principles of Neurology, 6th ed, p569)Receptor, Melanocortin, Type 4: A melanocortin receptor subtype found primarily in BRAIN. It shows specificity for ALPHA-MSH; BETA-MSH and ADRENOCORTICOTROPIC HORMONE.Receptors, Leptin: Cell surface receptors for obesity factor (LEPTIN), a hormone secreted by the WHITE ADIPOCYTES. Upon leptin-receptor interaction, the signal is mediated through the JAK2/STAT3 pathway to regulate food intake, energy balance and fat storage.Appetite Regulation: Physiologic mechanisms which regulate or control the appetite and food intake.Appetite Depressants: Agents that are used to suppress appetite.Appetite: Natural recurring desire for food. Alterations may be induced by APPETITE DEPRESSANTS or APPETITE STIMULANTS.Energy Intake: Total number of calories taken in daily whether ingested or by parenteral routes.Hypothalamic Hormones: Peptide hormones produced by NEURONS of various regions in the HYPOTHALAMUS. They are released into the pituitary portal circulation to stimulate or inhibit PITUITARY GLAND functions. VASOPRESSIN and OXYTOCIN, though produced in the hypothalamus, are not included here for they are transported down the AXONS to the POSTERIOR LOBE OF PITUITARY before being released into the portal circulation.Appetite Stimulants: Agents that are used to stimulate appetite. These drugs are frequently used to treat anorexia associated with cancer and AIDS.Rats, Zucker: Two populations of Zucker rats have been cited in research--the "fatty" or obese and the lean. The "fatty" rat (Rattus norvegicus) appeared as a spontaneous mutant. The obese condition appears to be due to a single recessive gene.Adiposity: The amount of fat or lipid deposit at a site or an organ in the body, an indicator of body fat status.Satiety Response: Behavioral response associated with the achieving of gratification.Adipose Tissue: Specialized connective tissue composed of fat cells (ADIPOCYTES). It is the site of stored FATS, usually in the form of TRIGLYCERIDES. In mammals, there are two types of adipose tissue, the WHITE FAT and the BROWN FAT. Their relative distributions vary in different species with most adipose tissue being white.Hypothalamic Area, Lateral: Area in the hypothalamus bounded medially by the mammillothalamic tract and the anterior column of the FORNIX (BRAIN). The medial edge of the INTERNAL CAPSULE and the subthalamic region form its lateral boundary. It contains the lateral hypothalamic nucleus, tuberomammillary nucleus, lateral tuberal nuclei, and fibers of the MEDIAL FOREBRAIN BUNDLE.Weight Gain: Increase in BODY WEIGHT over existing weight.Mice, Obese: Mutant mice exhibiting a marked obesity coupled with overeating, hyperglycemia, hyperinsulinemia, marked insulin resistance, and infertility when in a homozygous state. They may be inbred or hybrid.Body Composition: The relative amounts of various components in the body, such as percentage of body fat.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.Dorsomedial Hypothalamic Nucleus: An aggregation of cells in the middle hypothalamus dorsal to the ventromedial nucleus and bordering the THIRD VENTRICLE.Ventromedial Hypothalamic Nucleus: A nucleus of the middle hypothalamus, the largest cell group of the tuberal region with small-to-medium size cells.Paraventricular Hypothalamic Nucleus: Nucleus in the anterior part of the HYPOTHALAMUS.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.Receptor, Serotonin, 5-HT2C: A serotonin receptor subtype found primarily in the CENTRAL NERVOUS SYSTEM and the CHOROID PLEXUS. This receptor subtype is believed to mediate the anorectic action of SEROTONIN, while selective antagonists of the 5-HT2C receptor appear to induce ANXIETY. Several isoforms of this receptor subtype exist, due to adenine deaminase editing of the receptor mRNA.Injections, Intraventricular: Injections into the cerebral ventricles.Adipose Tissue, Brown: A thermogenic form of adipose tissue composed of BROWN ADIPOCYTES. It is found in newborns of many species including humans, and in hibernating mammals. Brown fat is richly vascularized, innervated, and densely packed with MITOCHONDRIA which can generate heat directly from the stored lipids.Infusions, Intraventricular: The delivery of a drug into a fluid-filled cavity of the brain.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).Dietary Fats: Fats present in food, especially in animal products such as meat, meat products, butter, ghee. They are present in lower amounts in nuts, seeds, and avocados.Eating Disorders: A group of disorders characterized by physiological and psychological disturbances in appetite or food intake.Neuropeptides: Peptides released by NEURONS as intercellular messengers. Many neuropeptides are also hormones released by non-neuronal cells.Pituitary Hormones: Hormones secreted by the PITUITARY GLAND including those from the anterior lobe (adenohypophysis), the posterior lobe (neurohypophysis), and the ill-defined intermediate lobe. Structurally, they include small peptides, proteins, and glycoproteins. They are under the regulation of neural signals (NEUROTRANSMITTERS) or neuroendocrine signals (HYPOTHALAMIC HORMONES) from the hypothalamus as well as feedback from their targets such as ADRENAL CORTEX HORMONES; ANDROGENS; ESTROGENS.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.Overnutrition: An imbalanced NUTRITIONAL STATUS resulting from excessive intake of nutrients. Generally, overnutrition generates an energy imbalance between food consumption and energy expenditure leading to disorders such as OBESITY.Receptor, Serotonin, 5-HT2B: A serotonin receptor subtype found in the BRAIN; HEART; LUNGS; PLACENTA and DIGESTIVE SYSTEM organs. A number of functions have been attributed to the action of the 5-HT2B receptor including the development of cardiac myocytes (MYOCYTES, CARDIAC) and the contraction of SMOOTH MUSCLE.Receptors, Corticotropin: Cell surface receptors that bind CORTICOTROPIN; (ACTH, adrenocorticotropic hormone) with high affinity and trigger intracellular changes. Pharmacology suggests there may be multiple ACTH receptors. An ACTH receptor has been cloned and belongs to a subfamily of G-protein-coupled receptors. In addition to the adrenal cortex, ACTH receptors are found in the brain and immune systems.Food Deprivation: The withholding of food in a structured experimental situation.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Receptors, Neuropeptide Y: Cell surface proteins that bind neuropeptide Y with high affinity and trigger intracellular changes which influence the behavior of cells.Corticosterone: An adrenocortical steroid that has modest but significant activities as a mineralocorticoid and a glucocorticoid. (From Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p1437)Satiation: Full gratification of a need or desire followed by a state of relative insensitivity to that particular need or desire.Thermogenesis: The generation of heat in order to maintain body temperature. The uncoupled oxidation of fatty acids contained within brown adipose tissue and SHIVERING are examples of thermogenesis in MAMMALS.Rats, Inbred OLETF: An inbred strain of Long-Evans rats that develops hyperglycemia, hyperinsulinemia, and mild obesity, mostly in males, that resembles non-insulin-dependent diabetes mellitus in humans. It was developed from outbred Long-Evans stock in 1983.Food Preferences: The selection of one food over another.Body Temperature Regulation: The processes of heating and cooling that an organism uses to control its temperature.