Tbh, I don't really know (been a while since I did this and researched it all), but I guess it would be taking in the right amount of protein and doing the right amount of exercise to prevent the erosion of muscle mass. I think where I went wrong was I continued to do no exercise and, while I only ate in 6-8 hour periods, I was still eating shit. I dropped some fat of course, but I'm fairly certain I dropped muscle too.