i thought it led to muscle loss as well as fat loss, muscle loss being undesirable ?
So, let's hear it ...
Bodybuilders explicitly do this to achieve low body fat percentages. I know. I have low body fat. I did exactly this. For most men, getting below ~14% body fat and into single digits requires you to do it. I’ve found that it’s nearly effortless in your 20s and requires actual calculations in your 30s and above.
The NIH has papers on this, bodybuilding.com has calculators for it…
Yes, the goal is to minimize the muscle loss. However, there is always some muscle loss.