Leptin is a hormone produced by your body that is involved in the regulation of appetite and energy expenditure. Leptin was initially thought to be the key to solving the current obesity epidemic due to its role in decreasing fat storage.
According to a 2004 article published by The Endocrine Society, the ob gene produces leptin, a 167 amino acid protein. Leptin functions as a hormone, or biological messenger, that allows communication between different tissues in the body.
A 2008 article published in the "Annual Review of Physiology" states that leptin is produced by fat tissue, known as adipose tissue. All individuals naturally produce leptin. The amount of leptin produced is directly correlated to the amount of fat tissue. Lean individuals tend to have lower serum concentrations of leptin relative to overweight individuals.
Leptin is secreted from adipose tissue and travels through the blood to the brain and other organs. Leptin acts to decrease energy intake and increase energy expenditure. According to the "Annual Review of Physiology," in the brain, leptin binds to leptin receptors, producing signals that lead to a decreased appetite. In tissues such as the muscle, fat oxidation is enhanced as a result of leptin signaling.
Leptin and Obesity
Leptin acts to limit the amount of fat storage and was initially hypothesized to be an important component for the treatment of obesity. However, the "Annual Review of Physiology" reports that diet-induced obesity is accompanied by a resistance to leptin action. The majority of obese individuals do not experience weight loss in response to leptin.
A genetic mutation in the ob gene can cause leptin deficiency. This condition, known as congenital leptin deficiency, is associated with increased hunger and severe obesity. According to an article published in the September 1999 edition of the "New England Journal of Medicine," congenital leptin deficiency can be successfully treated with leptin therapy. In this rare genetic condition, leptin therapy is able to decrease weight and fat mass primarily by decreasing hunger and energy intake.