As most any student will tell you, hunger and sleepiness seem to go together all too often. Recent findings from the Wisconsin Sleep Cohort Study offer new evidence that appetite and sleep are indeed linked, and that two hormones may cause people who get shortened sleep to feel hungrier when they are awake.
UW researchers, in collaboration with scientists from Stanford University and England's University of Bristol, confirmed in the Dec. 6, 2004 issue of Public Library of Science: Medicine that the duration of a person's sleep also affects the levels of ghrelin and leptin, two hormones that regulate appetite. Ghrelin triggers hunger while leptin suppresses it.
People with shortened sleep-fewer than eight hours a night-were found to have higher ghrelin and lower leptin levels, effectively increasing their appetite. This elevated desire to eat partially explains the increase in body mass typically associated with those who lack sufficient sleep.
Shahrad Taheri, clinical lecturer for the Henry Wellcome Laboratories at the University of Bristol, said the findings clarified what had been an ongoing mystery.
\For a long time, we have known about the association between those who sleep less and increased body weight,"" Taheri said in an e-mail. ""Nobody, however, really understood why this relationship existed.""
UW researchers have long studied the link between sleep and health. Terry Young, UW-Madison professor of population health sciences, started the Wisconsin Sleep Cohort Study in 1989 to more closely examine sleep disorders. Study participants, a random sample of Wisconsin state employees, spend a night once every four years in the UW sleep laboratory. According to Young, the study will hopefully call attention to the importance of sleep in maintaining nutritional health.
Regarding the common view of a healthy lifestyle, she said, ""Sleep has been left out of this picture.""
Paul Peppard, associate scientist with the UW-Madison department of population health sciences, agreed, adding that sleeping is ""as important to health as eating or breathing.""
When students are pressed to stay up late to study or work, they often turn to high-fat snacks to stave off hunger. This combination of junk food and reduced sleep is not only unhealthy, but hinders a student's performance in class as well.
""Good sleep will also allow better regulation of body weight and improve exercise performance,"" Taheri said.
Young warned against building up a ""sleep debt,"" or habit of shortened sleep. Napping could be a good way to supplement a night's sleep, she said, adding that adult humans are the only mammals that do not sleep twice a day.
Sleep-deprived students might consider adding a good night's rest to their resolutions this year, especially if they also want to stay in shape.
Sleep is ""going to be a lifelong issue that you pay attention to,"" Young said. ""The important thing is to be aware of it.\
