During muscle loss, are muscle fibers destroyed or do they just shrink?

Question

I read somewhere that muscle fibers stay around when you lose muscle but that they only shrink (hence why people can more quickly re-add muscle after a long break than when they first put it on).

1. Is this true, or during muscle loss, are muscle fibers consumed by the body?
2. If they do shrink, is there a time period for which they stay around? For instance, Christian Bale lost a dramatic amount of weight for his role in The Mechanic after he had gained a lot of muscle for Batman. Had he stayed at his weight in the Mechanic, is there some point at which he would have to rebuild all new muscle from scratch?

Update:

From what I could find, this link seems to indicate that fiber count stays the same, at least when atrophy is from lack of use (which is mainly what I was curious about) but I still wonder about the two questions above if anyone has any more details.

Answer 1

I used to workout a lot about 10 years ago then due to life ended up no longer working out. I started going back to the gym regularly about 1.5 years ago and I gained the muscle back very quickly. So quickly in fact that it took me a while to get used to the extra growth when going to bed at night.

And I'm now adding new muscle. I haven't researched it myself, but I don't think muscle fibers disappear. They may go in a deflated state waiting to be called upon again.

Answer 2

Biologically speaking- you can and will lose muscle fibers as part of regular aging or if you become stagnant. However, you can always build on muscle mass.

Referece: Bio 101 in college