I'm 48 (almost 49) and just beginning perimenopause. I've been primal for two months, have dropped 13.5 lbs (on top of 11 I dropped doing a CW diet from Jan-March.) I am, however, quite a bit heavier than you at 162 lbs. I need to lose at least another 20 lbs before I see much definition, I think.
I've been doing some bodyweight exercise, and can definitely see the beginnings of biceps. I bought some dumbbells yesterday, so give me a month or so and I'll let you know about the rest of my muscles