Training and losing muscle

I just turned 30 and have always been a pretty muscular guy. I was the weight lifter guy for many years before I started boxing etc...

I do alot more cardio and lift weights alot less. Anyone else notice a big change in body type when they started to train? I mean the me these days would beat the shit out of the me of 5 years ago but sometimes I wish I could retain more muscle. Is it simply higher protein intake. I am at 30 experiencing atrophy from old age or is it just very hard to keep muscle on whilst training at a hi level?

i'm 34 and noticed the same thing. i had more muscles back then, lots more. i just work on weights two days and mma 4 days a week. it is not possible to train hard in mma and look like brock lesner. trust me, i've tried.

testosterone levels dropping maybe?

possibly. Not sure ^^^

I am gonna start in on some tribulus.

Test starts dropping around that age for many men (!).

Likely reason in your case: too much cardio, not enough hypertrophy. Stop doing all your aerobic cardio/roadwork and switch it up to short, intense exercises like sprints, etc. That should help.

Also, make sure you're getting enough sleep. Keep your diet in check, etc.