you know I am going to go against what everyone else says and tell youthat you probably cando this for a period of time and not have to worry about losing your muscle. I have days where I eat alot less, and I think at a non competitivelevel we really should not worry about this to a certain degree...you can avoid the metabolism slowdow by having a few days at your reduced calorie level and then having a high calorie spike that is a few hundred over that level. Also, as we get older the number of calories we need declines so given that and your other issues I would say that if you stick to the carb cycling where you are getting adequete ratios of carbs and proteins lowereing your calories is not going to hurt you.

oh and most likely it was water or fat burned not muscle.