Leptin is a hormone produced by fat cells that helps regulate energy balance in the body. It signals the brain when the body has enough energy stored, which can help control appetite and metabolism. Higher levels of leptin typically reduce hunger, while lower levels can increase it, influencing food intake and body weight. Leptin plays a crucial role in maintaining body weight and preventing obesity. When people gain weight, their leptin levels usually rise, but some individuals may develop leptin resistance, where the brain does not respond effectively to the hormone. This can lead to overeating and difficulty losing weight.