Obesity is a common metabolic disorder characterized by an excess of body fat to the extent that it leads to complications. Body mass index (BMI) is calculated using the formula weight in kilograms/ height in meters. Visceral or central fat is termed ‘bad fat’ as it is more metabolically active and, through lipolysis. Etiology of obesity includes genetic susceptibility, environment and social influences, defective appetite regulation, reduced energy expenditure. Pro-opiomelanocortin (POMC) gene is located on chromosome 2 and it is synthesized in the pituitary, arcuate nucleus of the hypothalamus, solitary tract of the medulla, and several peripheral tissues such as the testes, ovary, placenta, duodenum, liver, kidneys, lungs, thymus, adrenal medulla and lymphocytes. Leptin is secreted by fat cells and feeds back to the hypothalamus and activates POMC, the gene expression of which could also be affected by NPY, opiods, sex steroids, glucocorticoids, dopamine and CRH. Leptin circulates bound to plasma protein and affects appetite regulation centrally. In mammals, brown adipose tissue (BAT) is a site of energy expenditure. Exposure to cold leads to sympathetic stimulation of brown adipocytes via norepinephrine (NE) binding to β-adrenergic receptors.
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