Mini MCAT passage: Hormonal control of weight loss

In 1994, biochemists identified a hormone called leptin that is involved in a positive feedback mechanism with the brain to promote weight loss. Leptin is a 167 amino acid molecule that is secreted by adipose tissue that binds receptors in the brain to stimulate satiety and promote weight loss.

Scientist studying the biochemical mechanisms driving obesity were interested in the effect leptin has on weight management and how it communicates with other hormones in the body. In mice, they knocked out various parts of the brain and assessed the effects of these knockouts on the regulation of satiety and appetite and resulting changes in weight. Partial results of their studies are displayed in the table below.