In order to build tissue and repair it, however, anabolism requires energy, as well as material with which to build. This energy and building material comes from the breaking down of larger, more complex material, a process called catabolism. As well as producing energy and building material, catabolism also breaks down material for excretion from the body. Both anabolism and catabolism are necessary for survival and good health Understanding these processes can help one make good decisions about exercise and diet. For example, when an athlete trains her muscles, her muscle fibers break down. However, the daily recommended amount of protein is all that is needed to meet the anabolic and catabolic needs of the body and thus repair muscles fibers.