Dont understand retaining fluid, losing fluid? explain
well, on top of wht the oither guy said...the human body puts pretty strict limits on natural muscle growth.....so even as a good nattie your not going to keep growing indefinalty.
so, in the offseason, when they tell you they are bulking and putting on muscle....it is the fats, sodium, water,and carbs that are giving them this perceived effect, and when they diet for the next contest, and they reduce those macros, and lose the subcutaneous water....they are probably lucky if during that bulking period produced even .0001 lb. of actual muscle. creatine is basically intercellular water-retention also that pretty quickly goes away.
also, it should be noted that this afformatnioned process also happpens to many people who juice incorrectly also.