[P]eople who consistently slept less than five hours a night had significant differences in the hormones leptin and ghrelin as compared with people who slept an average of eight hours a night. Leptin is produced by fat cells. Low levels of it are a signal of starvation and a need for a bigger appetite. Ghrelin, meanwhile, is produced by the stomach and is an appetite stimulant--the more ghrelin you have, the more you want to eat. The study subjects suffering a lack of sleep had 16 percent less leptin and nearly 15 percent more ghrelin than those who were well rested did. "In Western societies, where chronic sleep restriction is common and food is widely available, changes in appetite regulatory hormones with sleep curtailment may contribute to obesity," the team reports.
The study was carried out by the Public Library of Science: Medicine, a peer-reviewed medical journal that is, refreshingly, available online for free. Read the full report here.
I need to go get some sleep now. Wait, did you hear that fridge? It just called out my name!