This animation shows how the hormone leptin helps regulate appetite and weight.

Fat cells produce leptin in amounts proportional to the amount of fat tissue in the body. The animation illustrates how changes in the amount of fat tissue lead to changes in leptin levels and appetite. When a person eats less and their fat tissue decreases, their leptin levels also decrease. This change signals an area of the brain called the hypothalamus, which increases the person’s appetite. When a person eats more and their fat tissue increases, leptin levels increase and reduce appetite.

This animation is a clip from a 2004 Holiday Lecture Series, The Science of Fat. Depending on students’ background, it may be helpful to pause the animation at various points to discuss different steps in the feedback system.