It’s probably fair to say that most of us, at some point in our lives, will have the desire to lose weight. Not only do we want to lose weight, but we want to lose quality weight (i.e. losing fat and keeping/gaining muscle). To address weight loss goals, we need to focus on appropriate nutrition - mainly a caloric deficit along with optimizing macronutrients like protein. You may have also heard that another way to improve weight loss is to get enough quality sleep. Not only will quality sleep make you feel better, but it will also help you lose more fat and keep lean mass (especially muscle).
A randomized crossover study was conducted by Nedeltcheva et al,. to look at the effects of sleep on weight loss. It included 10 overweight participants (7 men and 3 women) around 41 years of age. The two groups were exposed to a 14-day calorie restriction where one group got 5.5 hours of sleep and another 8.5 hours of sleep. Measurements of loss of fat and fat-free mass, along with changes of hunger, the kinds of fuel being broken down for energy, and metabolic hormone concentrations were considered.
The results were profound. In fact, when sleep-deprived (5.5 hours), the fraction of fat loss was reduced by 55% (0.6kg vs. 0.8kg). When looking at the lean body mass of participants, the sleep-deprived group lost 60% more lean body mass than the group that got adequate sleep each night (2.4kg vs. 1.5kg).
From a hormonal perspective, those who were in the sleep-deprived group had higher levels of ghrelin. In times of energy restriction, ghrelin aids in fat-mass retention and stimulates appetite. For those in the sleep-deprived group, the effects of ghrelin were more pronounced - there was more hunger and more fat storage in the sleep-deprived group. Although the subjects’ caloric intake in this study was highly controlled, ghrelin has the ability to increase hunger, leading an individual to be more likely to (potentially) consume non-nutritive, calorie-dense foods. This all, of course, impacts weight loss.
One thought as to why the sleep-deprived group lost more muscle mass is because the brain was active for a longer period of time during the day, and glucose used as an energy source by the brain was likely made from the protein of skeletal muscle.
Looking to improve body composition and lose quality weight? Get adequate sleep!
Nedeltcheva, A. V., Kilkus, J. M., Imperial, J., Schoeller, D. A., & Penev, P. D. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of internal medicine, 153(7), 435–441. doi: 10.7326/0003-4819-153-7-201010050-00006 [doi]