In addition to fruitcake, eggnog and alcohol, sleeplessness can be added to the list of factors that may cause you to pack on a few pounds this holiday season.
Researchers from the University of Chicago and Stanford University have completed two studies that show lack of sleep causes changes in hormones that result in increased appetite and weight gain.
Scientists were amazed to find that hormone levels can be affected after as few as two nights of poor sleep, triggering alterations in the brain's chemistry that increase appetite.
These findings have been greeted with enthusiasm from sleep and diet experts, who consider them potentially groundbreaking in terms of changing the way they counsel patients on obesity.
"There is no question when you look at these two studies, we are definitely onto something," said Dr. Emmanuel Mignot, who headed the Stanford study. "What it should tell people is that those who are considering losing weight should think of healthy sleeping habits in the same sentence as healthy eating habits and good exercise habits."
Two Studies, One Conclusion
The two studies used different approaches to arrive at the same conclusion.
The group from Chicago, led by Eve Van Cauter, asked a small group of men in their 20s to restrict their sleep to four hours for two consecutive nights. They were then allowed to sleep for 10 hours the next two nights.
Van Cauter found not only that the men had a 24 percent greater appetite after the two nights of sleep deprivation, but they specifically craved high-sugar, high-salt and starchy foods.
In addition, analysis of their blood after the two nights of poor sleep found lower levels of leptin, a hormone that suppresses appetite, and higher levels of ghrelin, a hormone that triggers hunger.
Mignot's group looked at the sleep patterns of more than 1,000 individuals from Wisconsin and found that the less people slept, the higher their body mass index, a value that is often used to measure body fat. Results show that individuals who sleep less than eight hours a night on average are heavier than those who get a full night's rest.
The researchers also found that patients who averaged five or fewer hours of sleep per night had the same changes in leptin and ghrelin as those in the Chicago study.
Mignot found there were no significant differences between males and females in the way sleeplessness affected hormone levels or body weight.
A New Approach to Weight Loss?
Most physicians who have reviewed the studies agree that the findings may signal a new approach to combating obesity.
"There are plenty of reasons to get enough sleep, but this one might motivate people, especially if there is a real hormonal effect that shows getting enough sleep helps control weight," said Dr. Keith-Thomas Ayoub, associate professor of pediatrics at Albert Einstein College of Medicine in New York. "It might help people feel less blame and might help motivate them to take steps that avoid setting themselves up to fail."
However, many experts caution that simply increasing the amount of sleep each night is unlikely to result in significant weight loss unless patients also commit themselves to a healthy lifestyle.
"It isn't so simple just to tell people to sleep more and then they will lose weight," said Dr. Lee Kaplan, director of the Massachusetts General Hospital Weight Center in Boston. "People should see that when put into the total picture of all the things that cause people to gain weight, sleep is something that individuals should really aim to improve. But at the same time, sleep deprivation is only one contributor to the obesity puzzle."
Kaplan also cited food intake, stress levels and amount of exercise as other factors individuals should modify to lose weight.
'A Very Convincing Picture'
Mignot agreed that physicians should view sleep as just one facet on the battle against obesity. But he added that the two studies could be used as a springboard to finding ways to fix the hormonal changes that cause people to eat more and gain weight.
"I think these two studies are perfect in terms of complementing each other," he said. "When you put them together, they paint a very convincing picture. Now we need to look closer at why sleep affects these two important hormones and what we can do to change the balance in favor of losing weight."
Dr. David Katz, director of the Prevention Research Center at Yale University, looked at the results from a different angle.
"People laugh at commercials that promote money-making schemes that help you 'lose weight in your sleep,' " he said. "But guess what? This shows that if you sleep enough each night, you can lose weight in your sleep without paying a single penny."