One thing about situations where you want to lose weight, but want to gain muscle - as a generalism (for people who are already regularly training) and all things equal (ie no drugs) you can't really do those both things at the same time.

However, there is the "newbie effect" whereby untrained people find they will build muscle because of the new stimulus of resistance, whilst losing fat (because of the deficit in in vs out).

I guess what I'm trying to say is that as somebody new to training, you will find that works at first, gaining muscle, and losing fat - for a brief period. But after that, once your body because more accustomed to it, the body and metabolism doesn't work that way.

For trained people, the best you can hope for when losing fat (all things being equal) is that you don't lose any muscle.

So what I'm really trying to say is don't focus too heavily on bulding muscle whilst your trying to lose fat. You will gain some muscle in that process, simply as a result of being new to the stimulus, but focus on a period where you're trying to lose weight, and ideally bodyfat, then when your weight is more around your target goal, then start to focus on building muscle to meet your needs.