Have you ever been a victim of "sleep attack" during class lectures? I guess many of college students have felt some kinds of "sleep attack" during the early-morning lectures or after-lunch lectures.
Narcolepsy is one of sleeping disorder, and it causes the rapid and often unexpected onset of sleep. A new study of Devanjan Silder, a researcher of Sannford-Burnham Research Institute, explained the relationship between narcolepsy and weight problem.
There are two types of fat: white and brown. White fat stores calories while brown fat burns them.Lacking of the neuropeptide hormone, orexin*, that encourages hunger and wakefulness may cause "a lack of energy-burning brown fat."
Right now, there is not perfect treatment for the narcolepsy, but more research about orexin would help many people who are suffering from "sleep attacks."
"Orexin"- is a hormone that narcoleptics do not have. Orexin is related to our appetite and sleep. 
I did not know about the neuropeptide orexin relationship to narcolepsy before Kaori. Thanks for bringing it to my attention. Do you have the link to the study?