Red pepper (capsaicin annum L.) is used widely as a pungent spice due to alkaloid compound, such as capsaicin (8-methyl-N-vanillyl-6-nonenamide) which comprises 0.1-1% of red peppers is widely consumed as food adjuncts. A review is made on capsaicin, a natural anti-obesity substance which may have application to weight control and obesity. Capsaicin found to increase thermo genesis and its efficacy. The specialized capsaicin receptors are located on the taste buds within the papillae of the tongue. The receptors are responsible for detecting capsaicin is called transient receptor potential vanilloid-1(TRPV1). Capsaicin chemical structure allows it to bind to TRPV1. In the presence of capsaicin, a lipid portion of the receptor called P1P2 separates and allows calcium ions to enter the receptor cell. A pain message is then carried to the brain by substance P, a neurotransmitter. The bond between capsaicin and TRPV1 is temporary, so feeling of pain subsides when the bond is broken. TRPV1 is broadly distributed in tissues of the brain, bladder, kidneys, intestines, keratinocytes of epidermis, glial cells, liver, mast cells and macrophages. Capsaicin accelerates the secretion of catecholamine from the adrenal medulla in response to activation of the sympathetic nervous system. Catecholamine interact with adrenergic receptors in the liver or adipose tissue and increase energy expenditure by stimulating lipolysis and thermogensis and decrease accumulation of body fat in high fat diet.