If you are a boxer it does, in a sense, make you shorter. Consider this: you are 5'8" and weigh 150 walking around weight. That makes you a welterweight maybe even a jr. welter (depending on many things). You decide to improve to build srength by lifting weights and you put on 15 pounds of muscle, which doesn't come off so easily. Now you are a middle weight maybe a supermiddle and your opponents are guys that walk around at 170, 175 and stand 5'10" or more