This was said in another thread currently going on in this forum.
Christian Thibaudeau wrote:
I`m asking because if you didn't lose much strength, you likely didn't use muscle. When dieting down there will be a naturel drop in strength, even if you do not lose muscle. This is due in part to lowered energy levels but also to mechanical disadvantages.
I would expect a 5% loss in strength (on the big lifts), roughly, when dropping 15-20lbs of fat even if you do not lose any muscle. If you lost 5% or less on your big lifts (e.g. big lifts going down by 10-20lbs) then I would say that you didn`t lose any muscle. If you lost between 20 and 30lbs on the big lifts you probaly lost a small amount of muscles.
Still, I would say that it is quite possible that you didn`t lose much muscle at all but that you simply didn't have as much muscle as you though you had. A lot of people go on a bulking diet and grossly overestimate the amount of muscle they gain and then are surprised when they end up pretty much where they started whem they diet down.
There is what I call a bodyfat dead zone: between 12 and 18% body fat you pretty much look the same; not lean enough to look defined but not fat enough to look out of shape. So during a ''bulking'' period you could very well gain 15lbs thinking that you gained about 10-15lbs of muscle while in reality you might have gained 10lbs of fat and 5lbs of muscle.
OP, I would use this post to gauge how much lean mass you are retaining. If you see a large drop in strength on the big lifts, I'd reassess the situation and adjust your macros accordingly. There isn't any evidence to support what X said. As long as you diet in a controlled fashion (slowly), as encouraged by our very own Stu, you shouldn't see too much, if any, muscle loss. Most people just greatly overestimate how much muscle they were carrying to begin with, as said by CT in that post.