I think sweating heavily does contribute to bad body odors, but it seems like different people generate different levels of body odors. I've stood close to some people who have just left the gym and I can't smell anything at all. Other people come out smelling like old gym socks. There may be something about a person's body chemistry or diet or personal hygiene that makes a difference. I know I start smelling really bad in about an hour if I don't take a shower after a workout. My wife can just wash the sweat off her face and keep on going. She might look sweaty, but she doesn't have especially bad body odor.