How does leptin regulate appetite?

Leptin regulates appetite by signalling the brain to reduce hunger when sufficient fat stores are present in the body.

Leptin is a hormone that is primarily produced by the body's fat cells. It plays a crucial role in regulating energy balance by inhibiting hunger. The underlying mechanism of leptin's action involves communication with the hypothalamus, a region of the brain that plays a key role in controlling hunger and food intake.

When the body's fat stores are sufficient, fat cells secrete leptin into the bloodstream. This leptin then travels to the hypothalamus, where it binds to leptin receptors. This binding triggers a series of biochemical reactions that lead to the suppression of appetite-stimulating hormones and the production of appetite-suppressing hormones. As a result, the individual feels less hungry and eats less, which helps to maintain energy balance and prevent excessive weight gain.

However, when the body's fat stores are depleted, the level of leptin in the bloodstream decreases. This decrease in leptin signals the hypothalamus to increase the production of appetite-stimulating hormones and reduce the production of appetite-suppressing hormones. Consequently, the individual feels hungrier and eats more, which helps to restore the body's energy balance and fat stores.

In addition to its role in regulating appetite, leptin also influences other physiological processes, such as metabolism and immune function. It is also involved in the regulation of reproductive function, as low levels of leptin can inhibit ovulation and sperm production.

Leptin resistance is a condition in which the body's cells become less responsive to leptin, even when levels of the hormone are high. This can lead to overeating and weight gain, as the brain does not receive the signal to stop eating. Leptin resistance is thought to be a major factor in the development of obesity.

In summary, leptin plays a crucial role in regulating appetite and energy balance by signalling the brain to reduce hunger when the body's fat stores are sufficient. However, when leptin signalling is impaired, as in the case of leptin resistance, this regulatory mechanism can be disrupted, leading to overeating and weight gain.