You will not lose any muscle AT ALL as long as you maintain a lot of protein throughout the day. If you consume at least 120g (200 would be ideal) of protein per day, you won't lose muscle and still trim down the fat. How? This is just common sense, let me explain in few sentences.
All you have to do is to consume foods that does not contain much fat. This is pretty easy, meat doesn't contain much fat. Avoid dairy, only consume the amount needed for calcium, egg, rices, pasta, etc. You don't want to consume too much carbs either.
Now a little bit longer to give more encouragement if needed.
I am doing this for now (for the past week or so to continue for a month) to lose my stomach fat. I run every two days for 30 mins (I'm new to running, as in haven't run much for a long time) work out every two days on my body. I pretty much work out everyday in one way or another. I estimate that I am consuming only a thousand and five hundred calories with less than 40 percent daily fat. I am losing a significant amount of stomach fat already, only that the process is slower because I kind of do cheat with eating at night (after 7:30pm) few times or buying foods at restaurant. But if you don't cheat at all, I can promise that you will be losing fat while maintaining your muscle and will notice a significant result within two weeks. In my case, I am losing fat AND building muscle at the same time. How do you think that guy from Lord Of the Ring, History of Violence, Eastern Promise have the muscular body, yet is skinny (well not skinny but lean skinny in a normal way)? Just by maintaining same amount of calories as normal but contain huge percentage of protein. If an adult on 2000 calories daily consume 50 percent protein of that calories (can easily be done and has been done), he will pack on muscles but will not gain fat.
Makes sense doesn't it?