Danew, KMC, FightinIrish, KBC, & Nikiforos just gave you amazing advice. I suggest you take it.
I concur with your assessment that the whole overtraining dogma goes a little far. I’ve seen only a handful of people in my entire training life train with enough intensity for me to believe that they’re going to overtrain if they hit the weights more than 3x a week.
That said, it’s like Danew pointed out. If you have EVERYTHING dialed in. Nutrition, sleep, soft tissue work, mobility work, staying injury free… then rest of it is just properly building your work capacity and slow, steady progression.
I’m not saying this to discourage you. Quite the opposite… I WANT YOU TO SUCCEED. FightinIrish is making an amazing point that it took me years to realize, and I think a lot of people never do.
One of these you want to be your JOB the other is just going to be a hobby. So While MMA could benefit you, be a cool way to get in your cardio rather than just walking on the treadmill… Imo thats a great way to keep your bodyfat down…but if bodybuilding is your primary goal, and martial arts training negates your primary goal in ANY WAY, you need to drop it like first year English.
MMA training is a great way to keep your BF down but it’s hard to quantify what you’re doing… And in bodybuilding you need to be able to keep as detailed progress as possible (at least initially, when you’re a pro you can be more intuitive).
If right now your primary concern is size gain, then too much other activity may interfere with your recovery ability if you haven’t properly built up your work capacity. ESPECIALLY if you’re inactive most of the day- then your body isn’t used to stress. So research your recovery shit and learn how to keep your cortisol levels down and what not.
On top of this if you’re after BODYBUILDER type size then depending on your height (if you’re above 5’10) to look like one of the fucking behemoths then you need to be ~300-350lbs. So your primary concern is going to be lifting. And getting in as many calories as possible every hour for the rest of the week that you’re not eating.
If you need size, the quickest way is to forego ALL extra work except your lifting sessions and get in as many calories a day as you can… 10,000 whatever… fuck your health (lol)… Get as big and huge AND STRONG as possible BODYFAT BE DAMNED then diet down. And I guarantee that you’ll destroy 90% of people you stand with on the platform.
But of course no one wants to sacrifice not being ~12-15% bodyfat, or you don’t want to give up doing MMA, etc.
You’ve really got to prioritize.
What people don’t get is that lifting is the easy part. Really easy. Like you said, it’s what 3-6hrs a week… TOPS 12 if you’re on some steroid induced scheduling…
The hard part is the other ~162 hours a week that you have to be on the ball… eating, getting in rest, not burning unnecessary calories, knowing the effects of anything that goes into your body, etc.
Bodybuilding is not easy shit man… just as hard as MMA imo (you could argue its harder) and both have HUGE mental aspects to their game, and require a lot of sacrifice.
While I’m not sure if you have professional aspirations for either it sounds like MMA/BJJ is just a HOBBY to you at this point. Treat it as such, and treat bodybuilding like it is your primary means of feeding your family and you’ll succeed.