Final answer:
Leptin is a hormone produced by adipose tissues that induces feelings of satiety and regulates long-term food intake and energy expenditure. Its function is disrupted in obesity, leading to leptin resistance and overeating.
Step-by-step explanation:
The function of leptin is to regulate food intake and energy expenditure over the long term. This hormone is produced by adipose tissues and is crucial for the sensation of satiety, or fullness, following a meal.
When the body has an abundance of adipose tissue, more leptin is released, signaling the brain to reduce hunger and food intake. Conversely, with less adipose tissue and lower levels of leptin, the brain receives signals to increase hunger. In cases of obesity, there can be a condition known as leptin resistance, where despite high levels of leptin due to increased fat reserves, the brain does not properly signal satiety, leading to overeating and further weight gain.