But I thought muscle burned fat.
Nope.
Not directly at least.
Muscle is metabolically more expensive than fat but not to the extent many assume.
To boot, even if you were to add muscle and thus elevate the efficiency of your metabolism, genetics would still dictate where the fat 'burned' from.
And one more kicker is this:
To lose fat, you need to be in a caloric deficit.... be burning more energy than you're consuming.
To build muscle, you need to be in a caloric surplus... be consuming more energy than you're burning.
See the dilemma here?
*IF* building muscle on your upper body would translate to the direct 'burning' of said fat on your upper body (which isn't the case), you'd still be stuck in a quandary since to add said muscle you'd have to be in a caloric surplus.
I'll note that trainees who are carrying a lot of excess fat or who are very untrained can lose fat and build muscle simultaneously, but it's not going to happen long enough to make an overly appreciable difference.
So since I keep those muscles in use more often they burn fat more efficiently, or maybe I'm wrong.
Not quite. Muscles don't burn fat. Caloric deficiencies do. By this, I mean fat is a storage depot for excess energy. If you're not consuming enough energy (calories) to facilitate your body and activity, the energy is made up for by 'burning' some fat.
I know genetics can influence the shape of your body but I would be leaner if I had some type of good upper body work out.
You would be leaner if you lost the fat covering the muscles you currently have on your upper body.
Sure, preserving the muscles you do have is important while dieting. And I'm not trying to prove weight training the entire body isn't important at all, either.
If I didn't climb those stairs I believe my legs would be bigger but I'd still be the same shape. You get where I'm coming from???
Not really, sorry.