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Sleep deprivation decreases testosterone levels and muscle protein synthesis


Poor sleep is associated with worsened muscle mass and function, but more research is needed to explore the mechanisms behind this association.

The study

This randomized, crossover study sought to determine if acute sleep deprivation affects muscle protein synthesis, muscle protein degradation, or anabolic and catabolic hormones.

For that purpose, 13 people were subjected to one night of total sleep deprivation and one night of normal sleep, separated by at least four weeks. After both nights, the investigators collected blood samples to evaluate blood markers of catabolism (cortisol) and anabolism (IGF-1, insulin, testosterone).

After both nights, the investigators also assessed postprandial muscle protein fractional synthesis rate (FSR) by assessing the incorporation of L-phenylalanine into muscle tissue. For that purpose, they used continuous infusion of L-phenylalanine from 10:00 a.m. to 3:00 p.m., provided a mixed-macronutrient meal at noon, and collected muscle biopsies of the vastus lateralis at 1:00 p.m. and 3:00 p.m.

The results

Compared to normal sleep, total sleep deprivation reduced postprandial muscle protein FSR by 18% and testosterone area under the curve (AUC) by 24%. Whereas wake-time cortisol was higher in the control group (cortisol typically increases during later sleep stages), midafternoon cortisol was higher in the sleep-deprived group. Insulin and IGF-1 did not differ between groups.

Muscle gene expression was not a prestated outcome of the study, but the authors assessed it anyway. They found no differences in genes associated with the circadian rhythm or muscle protein degradation.


This study shows that sleep loss can impair muscle gain, and other studies have shown that it can promote fat gain.[1][2][3][4][5][6] In people who lose weight, sleep loss can decrease fat loss and increase muscle loss.[7] In short, sleep loss has a detrimental effect on body composition.

While the study wasn't sufficiently powered to assess differences between genders, the authors noted that all males, but not all females, experienced a decrease in protein synthesis when sleep deprived. This is consistent with the results of a study we reviewed last month, which reported that sleep deprivation impaired athletic performance to a greater degree in men. Since men have more testosterone, the decrease in testosterone levels caused by sleep deprivation might, to some extent, explain the difference.

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