Good Sleep is needed, not less.

If you are planning on doing a “summer cut” to lean down, you probably are spending much attention on your training and nutrition. But one factor that oftentimes gets neglected is the effect of proper sleep.
–
A 2010 study investigated the effects of sleep on body composition in people that maintain a moderate caloric deficit [1]. The researchers found that sleeping around 8 hours per day results in more fat loss and muscle preservation when compared to sleeping only around 5 hours per day.
–
The difference was quite large as well. The participants that slept ~8h lost about 50% more fat than the group sleeping 5h. But something to keep in mind here is that the poor sleep may have made it harder for the 5h group to stay adherent to their diet.
–
With that said, more recent research by Wang et al. supports that sleep restriction tends to negatively affect muscle preservation and fat loss while on a fat loss diet [2]. So it’s beneficial to take a good look at your sleeping habits if you are trying to lose fat while (at least) maintaining muscle.
–
Now, this obviously doesn’t mean you will always lose muscle in a diet if you struggle with sleep. But improving your sleeping habits is one of the low-hanging fruits when it comes to enhancing your overall fitness results. For most people, 7-9h of sleep in a day is a good aim.
–
References:
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2951287/
2. https://www.ncbi.nlm.nih.gov/pubmed/29438540