Sleep: the Silent, Key Player in Fat Loss

Losing Sleep Makes It Harder to Lose Fat

Dropping body fat takes a lot more than cutting calories and upping your cardio. You can eat grilled chicken and steamed broccoli and hit the StairMaster daily until the cows come home, but fat loss won’t become a complete reality unless you get a good night’s sleep. If you don’t get adequate sleep each night, you’ll have a harder time regulating your bodyweight. While lack of sleep has historically been linked to weight gain and obesity, this sleep-weight gain connection has been reinforced by a new study published in the journal Sleep.1

Sleep researchers from the Department of Exercise Science at the University of South Carolina found that when dieters were consistently deprived of sleep during weeknights over an eight-week period, they lost less fat— and more lean muscle— than dieters who consumed the same amount of calories daily but slept more. Even though sleep-deprived dieters, who slept between 6 and 6.5 hours during the week, slept an extra hour each weekend night, they still lost less fat than people who slept more. Among the sleep-restricted dieters who lost weight, no one lost more than 58 percent from fat, or less than 39 percent from lean muscle. As for people who slept between 7 and 7.5 hours per night, at least 83 percent of their weight lost came from fat, while 17 percent was from lean muscle.

“Approximately one hour of sleep restriction on five nights a week,” the study’s authors wrote, “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 Sleep study is not the first research to demonstrate that sleep deprivation contributes to the reduction of muscle mass instead of fat during reduced energy intake, compromising the effectiveness of caloric restriction. A study by Nedeltcheva et al.6 put 10 subjects on identically low-calorie diets for two weeks, where one group slept for 5.5 hours per night and the second group slept for 8.5 hours per night. At the end of the two-week period, all subjects lost a similar amount of weight but there were significant differences in body composition. The group that only had 5.5 hours of sleep lost 55 percent less fat mass and 60 percent more muscle mass, when compared to the group that slept for 8.5 hours per night.

Adequate sleep prevents obesity. Getting enough sleep is critical for weight control— according to an editorial in the American Journal of Clinical Nutrition.2 People who sleep longer have a lower body mass index, which is a measure of the proportion of weight to height. Inadequate sleep increases total food intake, snacking frequency, the number of meals consumed per day and the consumption of high-calorie foods. Poor sleep patterns encourage people to eat for pleasure (hedonistic eating patterns). The editorial concluded that sleep is as important as physical activity and proper nutrition for good health.

Energy balance and weight gain. Lack of sleep disrupts energy balance, which determines whether you gain weight, lose weight or stay the same— according to a literature review and meta-analysis conducted by David Allison and colleagues from the University of Alabama at Birmingham.3 Sleep deprivation causes increased appetite by increasing a hormone called ghrelin, which promotes appetite. Sleep deprivation also reduces leptin, a hormone that normally suppresses appetite. Some studies have found that inadequate sleep increased the risk of obesity by 200 percent. Inadequate sleep was also linked to diabetes and high blood pressure. Sleep disturbances are surprisingly common in children and adults and can cause serious health problems, such as memory loss, coronary artery disease, stroke, daytime sleepiness and contribute to automobile and workplace accidents.

Sleep loss and the biological clock. Sleep deprivation affects AMPK and SIRT1 (fuel-sensing molecules) function by fundamentally influencing our biological clock— which is a set of biochemical pathways that regulate specific functions based upon the time of day. Lack of sleep disrupts the natural patterns of our biological clock, increasing the inclination to eat. Alterations in leptin and ghrelin from less sleep increase food intake by as much as 100 additional calories per day for every hour of sleep lost, while also increasing body fat by approximately 3 percent after similar sleep deprivation.4,5

Since energy consumption is very low while we sleep, which lowers the immediate demand for energy, sleep persuades the biological clock to turn down energy production by inactivating AMPK and SIRT1 while also turning on additional pathways that store energy while you sleep. Too little sleep skews the biological clock— shifting the preference from energy storage to energy production by activating AMPK and SIRT1. Eventually, this reduction in energy storage deceives the body into believing there is a shortage of energy— stimulating greater food consumption that the body stores primarily as body fat.

Other research has shown that sleep loss also has a negative influence on testosterone production, causing a weaker anabolic environment that precludes muscle growth. Fortunately, researchers have shown that certain nutritional supplements can increase the quantity and quality of sleep— and reduce insomnia, thus making you feel more rested and energetic while encouraging fat loss and testosterone production.


  1. Influence of sleep restriction on weight loss outcomes associated with caloric restriction. Sleep, Volume 41, Issue 5, 1 May 2018, zsy027,
  2. American Journal of Clinical Nutrition, 101: 5-6, 2015.
  3. Obesity Reviews, 16: 771-782, 2015.
  4. Taheri S, et al. Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Med 2004;1(3): p. e62.
  5. Rontoyanni VG, Baic S and Cooper AR. Association between nocturnal sleep duration, body fatness, and dietary intake in Greek women. Nutrition 2007;23(11-12): p. 773-7.
  6. Nedeltcheva AV, et al. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med 2010;153(7): p. 435-41.

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