Which hormone is known to decrease post-bariatric surgery, contributing to weight loss?

Ghrelin is the hormone that plays a significant role in appetite regulation, and its levels are known to decrease following bariatric surgery, which contributes to weight loss. Ghrelin, often referred to as the "hunger hormone," is primarily produced in the stomach and stimulates appetite, increases food intake, and promotes fat storage. After bariatric procedures, particularly those that involve gastric restriction or bypass, the production of ghrelin is reduced due to changes in stomach anatomy. This decrease in ghrelin levels leads to reduced hunger and calorie consumption, thus aiding in weight loss.

In contrast, leptin, while essential for regulating energy balance by inhibiting hunger, typically remains elevated in obese individuals, as they often have developed leptin resistance. Cholecystokinin (CCK) is a peptide hormone that aids in digestion and is released after eating; its role is more transient in terms of satiety rather than long-term weight loss modulation. Insulin, while crucial for glucose metabolism and energy storage, does not primarily contribute to the post-surgical weight loss effects seen as a reduction in appetite.

Given these roles, the decrease in ghrelin after bariatric surgery directly correlates with a reduction in appetite and food intake, which is