Of course, everyone knows that cutting back on calories is a key component to losing weight. But do you know what else plays an important role in the ability to slim down?
Deprive yourself nightly of an adequate amount of sleep and you'll have a harder time regulating your body weight. Scientifically, this relationship has emerged time and again in previous research, where lack of sleep is also linked to weight gain and obesity. Now the connection is being reinforced, given the results of a small study which showed that when would-be dieters get less sleep, the ability to lose body fat becomes more difficult.
Sleep researchers from the Department of Exercise Science at the University of South Carolina learned that when dieters were systematically deprived sleep over an eight-week period they lost less fat – while losing more lean muscle – than their counterpart dieters who consumed nearly the same amount of daily calories.
Each weeknight, dieters on sleep restriction, or SR, got one fewer hour of shuteye, sleeping between 6-to-6.5 hours. And even though they regained an extra hour each weekend night, among the weight they lost no one dieter lost more than 58 percent from fat, or less than 39 percent from lean muscle.
By comparison, among dieters who slept between 7-to-7.5 hours per night, at least 83 percent of the weight lost came from fat while 17 percent was from lean muscle.
"Approximately one hour of sleep restriction on 5 nights a week," the study's authors wrote in their paper, "led to less proportion of fat mass loss in individuals undergoing hypocaloric weight loss, despite similar weight loss. Sleep restriction may adversely affect changes in body composition and 'catch-up' sleep may not completely reverse it."
The study, titled "Influence of sleep restriction on weight loss outcomes associated with caloric restriction," was published in the journal Sleep.
A total of 36 overweight or obese adults between the ages of 35 and 55 were involved, 21 of whom were engaged in calorie restriction and less sleep restriction, or CR + SR. The other 15 were tasked solely with calorie restriction, CR. Roughly 80 percent of the participants were female, 61 percent were African-American and according to the authors, all "had similar average age, body composition, TIB [total time in bed, including naps], and TST [total sleep time] at baseline." The classification of obesity was determined using the body mass index, or BMI.
Participants in the CR + SR group consumed an average of 1,450 calories daily, down 325 calories from their normal intake. The CR group ingested 1,390 calories daily, down nearly 200 from an ordinary day. All 36 adults lost roughly 7 pounds apiece, but the difference in the fat-to-muscle ratio between the two groups emerged as the most significant metric.
The authors added that an "important strength of this study," which was supported by a grant from the American Heart Association, "is the relatively long duration of the intervention (8 weeks). This duration was longer than previous sleep restriction studies in the context of dietary weight loss."
As for its limitations, certainly, the sample size was an issue, which hopefully will be addressed in future studies. Another was the participants' role in counting calories and the self-reporting of data. Nonetheless, the results helped reinforce what we already know about the association between weight control and a good night's sleep.