How much a person sleeps at night can impact their weight. This is because the amount of sleep a person gets can affect certain hormones, specifically the hormones leptin and ghrelin, that affect appetite. Leptin and ghrelin work in a kind of "checks and balances" system to control feelings of hunger and fullness. Ghrelin, which is produced in the gastrointestinal tract, stimulates appetite, while leptin, produced in fat cells, sends a signal to the brain when you are full. When you don't get enough sleep, it drives leptin levels down, which means you don't feel as satisfied after you eat, and increases ghrelin levels, stimulating your appetite so you want more food. The two combined can set the stage for overeating, which in turn may lead to weight gain.