There really is an easy way to lose body fat.
You can sleep it off, according to researchers from the University of Chicago.
The researchers studied 10 overweight men and women for two separate two-week periods in a sleep lab. During both periods, participants in the study ate the same calorie-restricted diet. During one period, participants slept for 8.5 hours a night. During the other, they slept for just 5.5 hours.
The researchers found the participants lost the same amount of weight during both periods, an average of about 7 pounds.
But during the sleep-restricted period, the participants lost mostly muscle.
"The amount of human sleep contributes to the maintenance of fat-free body mass at times of decreased energy intake," concluded the study, which was funded chiefly by the National Institutes of Health and published in the Annals of Internal Medicine. "Lack of sufficient sleep may compromise the efficacy of typical dietary interventions for weight loss and related metabolic risk reduction."
"I hope there are more studies like this," said Christine Mackey, who practices internal medicine at Allegheny General Hospital. "It makes sense physiologically."
She said the amount of sleep you get has an effect on the production of ghrelin, a hormone the body produces that is essential to weight management. It stimulates the liver to produce more sugar, slows metabolism and decreases the body's ability to burn fat.
An earlier study indicated that "volunteers who had just two hours less of sleep [each night] had a rise in their level of ghrelin," Dr. Mackey said. "They experienced more hunger and they lost less fat."
Another important hormone affected by the amount of sleep we get is leptin, said Ryan Soose, director of the Division of Sleep Surgery at the University of Pittsburgh Medical Center.
"Leptin is a hormone released by fat that provides information to the brain about energy metabolism," Dr. Soose said. "Reduced sleep is associated with lower leptin levels. That correlates with insulin resistance [a precursor to diabetes] and is related to other hormonal changes associated with weight gain."
Sleep deprivation retards weight loss because "if your body doesn't get the rest it needs, it basically 'believes' that it is under constant threat," said Kristina Sargent of ChicagoHealers.com, a Chicago health care network with 200 practitioners that promotes natural medicine and a holistic lifestyle. "If you are under prolonged stress, the body refuses to give up stored fuel. Fat is designed as a storage tank for energy, and regular rest allows the body to slow down and release storage fats."
Dr. Mackey agreed. "If you have just a little bit of chronic sleep deprivation, that is going to be a stress to the body," she said.
Earlier studies had showed the effect of sleep deprivation on the production of ghrelin, leptin and other hormones and had indicated that children who sleep less are at greater risk for obesity. Dr. Soose said the Chicago study is an important contribution to the body of knowledge on the subject because it demonstrated in a randomized clinical trial the effect of sleep on fat loss.
The takeaway for him, Dr. Soose said, is that "insufficient sleep duration is not just associated with feeling tired the next day. It actually has dramatic changes on a hormonal level that are associated with weight gain and obesity, diabetes and a whole host of other medical problems."
To sleep better at night, Ms. Sargent recommends that you stay away from alcohol after 7 p.m. and turn down the lights right after dinner, as darkness can stimulate melatonin production that will help you feel sleepy.
Correction/Clarification: (Published November 13, 2010) A Nov. 1 story about the benefits of sleep misspelled the last name of Ryan Soose, otolaryngologist and sleep disorders specialist at the University of Pittsburgh Medical Center.
Jack Kelly: firstname.lastname@example.org or 412-263-1476.