I don't know of any studies, but weight is certainly a load on the heart and joints.
Good point. I don't mean to be fixed in my definitions, but I agree that I've presented them that way. I've also known 350lb linemen from my college who could outrun skinny bastards in the 40, but that doesn't change the point. The upper limit of their speed, quickness, and flexibility is set lower due to their incredible size. Ronnie Coleman would find quickness and flexibility more easily attained were he 100 pounds lighter.
I admit I'm a little weird with my response, but here me out. It's about making yourself feel self-fulfilled. That is how I define ego. There is internal focus, and there is external focus. I call internally focus dominated people "ego-centric." But that's just me, and I'm likely one of them.
I don't mean this to be scathing even if it comes across that way, but those are self-centered and maybe even egotistical, pride-centered statements. I have them too, but we need to recognize them for what they are.
Being lean and muscular for the sake of impressing and self-fulfillment is prideful and (dare I say) sinful, but improving ones health is not. The motivators are what I'm questioning.