First of all, if you are doing strength training on a regular basis, you´re recovery capacity is reduced if you don´t get enough sleep. Most people know that already.
There are however 3 more insidious consequences of not getting enough quality sleep every night.
1. If you restrict your sleeping time you generally are hungrier! (1)
When you are trying to lose fat this can indirectly hamper your progress by making you hungrier than usual, especially cravings of carbs can increase.
2. If you are not getting enough sleep and are in a caloric deficit, the amount of fat you lose is reduced by about half. If that wasn´t enough, the amount of fat-free mass (muscle!) you lose can increase by 60 % (2)!
Nutrient partitioning – in which parts of the body the stuff that you eat ends up in- is going to be worse with less sleep.
Just increasing your sleep time can therefore lead to better body composition.
3. Your intelligence suffers and you function poorly (3)
This one is big. A very well controlled study showed that people sleeping 6h or less for 14 days showed similar decreases in cognitive performance than those not sleeping at all for 2 nights straight!
Whats even more interesting is that the subjects who slept <6h hours per night showed a relatively sudden decrease in mood over the days but then reached a plateau and seem to have adapted to the chronic level of sleep deprivation.
In contrast, the subjects who were kept up for 3 days straight felt a linear worsening of subjective fatigue.
So next time you hear someone say „It´s fine, I can get away with sleeping 5 hours per night, I´m used to it!“ tell him that his sleep debt is costing him big time and they can´t rely on their subjective feelings in this case.
Key message: Get your sleep in. It is more important than you might think!
-Thomas
References
(1)Brondel, L., Romer, M. A., Nougues, P. M., Touyarou, P., & Davenne, D. (2010). Acute partial sleep deprivation increases food intake in healthy men. American Journal of Clinical Nutrition, 91(6), 1550–1559.
(2)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.
(3)Van Dongen, H. P. A., Maislin, G., Mullington, J. M., & Dinges, D. F. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep, 26(2), 117–26.
