**Core Concept:** The central controllers of appetite are neurotransmitters and hormones that regulate food intake and energy balance in the body. These include leptin, insulin, ghrelin, and cholecystokinin (CCK).

**Why the Correct Answer is Right:** Leptin is a hormone secreted by adipose tissue in response to fat stores. It travels to the hypothalamus, where it inhibits food intake and promotes energy expenditure. Leptin helps maintain energy balance by decreasing appetite.

**Why Each Wrong Option is Incorrect:** Insulin is a hormone that lowers blood glucose levels by promoting glucose uptake by cells and inhibiting hepatic glucose production. Insulin does not directly affect appetite.

Ghrelin is a hormone secreted by the stomach's fundic cells in response to fasting or low blood glucose levels. It travels to the hypothalamus, where it stimulates food intake and reduces energy expenditure, thus increasing appetite.

Cholecystokinin (CCK) is a hormone released by I cells in the duodenum in response to ingestion of fatty acids, proteins, and carbohydrates. It travels to the hypothalamus, where it stimulates food intake, reducing satiety and increasing appetite.

**Clinical Pearl / High-Yield Fact:** Appetite is a complex interplay between various hormones and neurotransmitters. Understanding these regulators is crucial for managing conditions like obesity, anorexia, and diabetes.

**Correct Answer:** C. Cholecystokinin (CCK) does not decrease appetite. It stimulates food intake and reduces satiety, thus increasing appetite.