Poor sleeping habits impair normal cognitive and metabolic function and are associated with worse mental and physical health outcomes in the short- and long-term. Sleep loss may also interfere with protein synthesis, driving skeletal muscle losses, a risk factor for obesity, type 2 diabetes, and frailty. Authors of a recent report measured the effects of sleep deprivation on muscle protein synthesis.

Skeletal muscle is metabolically active. Having more muscle mass promotes insulin sensitivity and reduces the risk of developing type 2 diabetes. Previous research in rats has shown that sleep deprivation reduces the activity of enzymes that build muscle, such as testosterone and insulin-like growth factor (IGF)-1, and increases the activity of enzymes that break down muscle, such as cortisol. The same shift in hormones may occur in humans deprived of sleep.

Thirteen young adults (average age, 21 years) completed two testing days in random order in which they experienced one night of sleep deprivation and one night of normal sleep. On one day, participants consumed a standardized meal at home at 7 p.m., reported to the laboratory at 9 p.m., and were not permitted to sleep until 7 a.m. During the night, participants were allowed to engage in quiet activities and eat low-protein fruits and vegetables as snacks. On the other day, participants consumed a standardized meal at home at 7 p.m., then slept at home between 10 p.m. and 7 a.m.. On both days, researchers collected blood samples and muscle tissue samples, following a standardized breakfast meal.

One night of sleep deprivation reduced muscle protein synthesis by 18 percent. This was accompanied by a significant 24 percent reduction in serum testosterone levels in male participants and a significant 21 percent increase in cortisol levels in all participants. There was no difference in plasma insulin or IGF-1 levels and no difference in markers of muscle protein degradation.

The authors concluded that just one night of sleep deprivation interferes with muscle protein synthesis. Chronic sleep deprivation may cause loss of muscle mass due to long-term suppression of muscle-building enzymes.

The good news is exercise is known to counter at least some of the negative effects that sleep loss has on metabolism. For example, high-intensity interval training before a night of sleep deprivation attenuated the increase of glucose, insulin, and free fatty acids caused by lost sleep in healthy males.

• Link to full report.
• Learn more about cortisol and sleep in this episode featuring sleep expert Dr. Matthew Walker. And watch this short video on the hidden connection between sleep and dementia.