Used to in the early 2000s, but too many people started passing out on stage, blood congealing, etc. Now most are able to come in contest ready with proper carb and water manipulation. Carbs are required in order to subcutaneously hold water, hence if you ever hear the term “spilling over”. Diuretics are only to be used if you f**k up your peak prior to the show by taking in too many carbs and end up holding water/spilling over.