Appreciate your detailed response. This article was written quite some time ago.

I now train Muay Thai and yes, there's a ton of running, jumprope, and general bag work cardio.

While there has been some muscle loss, even I don't look anorexic.

I've now concluded that it's the combination of an extreme calorie deficit + intense cardio that causes severe muscle wastage.

Thanks for reading and responding Attila!