Most of the participants in the current study were women, and more than half were African-American. They were 45 years, old on average, and had a body mass index (a measure of weight relative to height) in the obese range.
Before the experiment, people in the sleep-restriction group said they consumed an average of about 1,775 calories a day, and during the experiment, they cut back to an average of 1,454 daily calories. In the other group, people started out on about 1,575 calories a day and cut back to about 1,389 calories during the experiment.
Without sleep restriction, people typically got about 7 to 7.5 hours of sleep each night before the experiment and continued to do so once the experiment started.
In the sleep restriction group, people got about 6 to 6.5 hours of sleep on weeknights and about 8 to 9 hours of sleep nightly on weekends.
All of the participants picked up prepared lunches and dinners for four days each week and received sample meal plans and help from a registered dietician.
Among the people who didn't cut back on sleep, a much larger proportion of the weight loss was in the form of fat rather than muscle mass: For half of this group, at least 83 percent of the weight they lost was fat tissue and less than 17 percent was lean tissue.
The people on sleep restriction tended to lose a higher proportion of lean tissue: For half of this group, at least 39 percent of the weight they lost was lean muscle and no more than 58 percent was fat.
One limitation of the study is that researchers relied on participants to count calories and accurately recall and report everything they ate and drank instead of having their intake measured by researchers for an exact calorie count.
Even so, the results add to evidence that good sleep habits may be a key ingredient for weight loss, said Marie-Pierre St-Onge, a nutrition researcher at Columbia University Medical Center in New York City who wasn't involved in the study.
"Drastically cutting sleep has been shown to increase food intake and now there is increasing evidence that sleep loss can have counter-productive effects for weight management," St-Onge said by email.
Ideally, people trying to lose weight should get about 7 to 8 hours of sleep each night, St-Onge added. More sleep than this isn't necessary to lose weight, but people who typically get less than this may want to start getting more rest if they're overweight or obese.
"If sleep is inadequate, this may be a reason for the extra weight," St-Onge said. "To promote better sleep at night, shut down electronic devices a few hours before bedtime, dim room lights, avoid caffeine and other stimulants in the evening, set a cool bedroom temperature, reduce noise and get some exercise during the day."
(This story has not been edited by Devdiscourse staff and is auto-generated from a syndicated feed.)