About Leptin
Leptin is the 'satiety hormone' secreted by fat cells to signal the brain that energy stores are sufficient and eating should stop. Paradoxically, obesity is typically associated with very high leptin alongside leptin resistance — the brain stops responding to its signal, perpetuating hunger and fat accumulation. Very low leptin (seen in severe caloric restriction or low body fat) suppresses reproduction, immunity, and thyroid function, reflecting the body's emergency response to perceived starvation.