Leptin

Leptin is your body’s “fullness hormone.” It tells your brain you have enough energy stored. In obesity, the brain can become resistant to leptin, so you never feel truly satisfied.

Leptin is an adipokine secreted by adipocytes proportional to fat mass. It acts on hypothalamic receptors to suppress appetite. Leptin resistance is common in obesity, contributing to hyperphagia.

Understanding leptin explains why willpower alone is often insufficient for weight loss. Medical treatments that improve leptin sensitivity are under active research.