So I am a 37 year old software dude who's trying to get/stay in shape. In the past, I've done a lot of what I'd call "crossfit-light" type exercise. Mainly bodyweight squats, lunges, pushups, yoga, plank burpees, jumping, etc. That sort of stuff took me from being a couch potato to being less embarrassed to take my shirt off in public.
Note: I am genetically pre-disposed to being very thin/lanky. Even when I was my heaviest, I just had a beer-belly attached to my pole-bean body. Gaining real bulk/muscle is difficult for me, both genetically, and because I have back problems (herniated disc from minor arthritis in L4-L5) and so can't do a lot of heavy lifting.
Lately, I have started taking boxing training (without sparring) as a way to increase my high-intensity cardio, and I really like it. I'd like to do 1-2 sessions (30-40min each) of cardio-boxing each week, with mitts, heavybag, footwork, etc. I'd also like to keep doing 1-2 sessions of my previous workout routines per week (planks, burpees, yoga, pushups, etc), with a lot focusing on my legs/shoulders, which I'd like to get bigger.
My question is basically: should I take creatine and high protein foods to help ensure that I'm not loosing muscle to the boxing/cardio work I'm doing, or is creatine supplimentation wasteful/harmful if I'm not doing heavy-lifting in the gym constantly.
I'm aware that you can't really lose fat and gain muscle at the same time. I'd like to tone up a little, but I don't have a ton of fat to lose as it is (just a remnant of my beer belly). Ideally I'd gain some visible mass in my legs/shoulders. I'm OK with the fact that its not optimal to want to lose fat and gain muscle at the same time, I just don't want to be totally wasting my time here, or hurting myself with the creatine.