I mean how much muslce you gunna lose in 24 hrs on a fuck ton of gear that holds muscle.
I don't know if you have ever competed, but it is not about losing muscle.
I will give you a real world example. There was a 9 pound difference between my carb depleted state 5 days prior to weigh in (6 days prior to competition) and my weigh in weight. That was 9 pounds of carbing up.
So you get rid of all the fat in the months prior to the show. Somewhere around a week before, you deplete your muscles of glycogen. You look sickly and stringy and nasty.
Then you "carb up," which really means several days of adding glycogen and water to your muscle. You are not "adding muscle," but you take that stringy look and fill those muscles up like balloons.
If your prep was done well, there is nothing between the skin and muscle. As the muscles swell, they push up tight against the skin.
There is a maximum point - and once you pass it, they call it "spilling over." You'll know when this happens because you will start to look blurry. All the striations begin to go away. It is water placing itself in between the muscle and the skin.
So you are playing this game of filling up your muscles to their maximum capacity without spilling over and blurring out all of that great definition.
You then spend the next two days (weigh in day and competition day) staying full without spilling over. It is a constant back and forth on carbs and water.
Now if you are Dorian Yates, or some similar behemoth, that is a lot of food to push in. I am much smaller, and I used foods that pack a lot of carbs in a small package (nothing like eating in prep). But Dorian has a lot of muscle to "blow up" with water (glycogen carries three parts water with it), and if he fasted, his muscles would quite literally get a deflated look, like a balloon with some of the air let out.
On Monday, I look sickly, like I am dying. On Saturday I am taking heavyweight and overall. That is how it works. Fasting would have me looking more like the sickly and dying look, not a good look for the stage. On stage, you have to maximize that carb up and swell up the muscles but back off if there is a hint of you looking "watery."
So fasting is a bad competition strategy. Just my two cents. I do not train or prep any pros. I did, however, stay at a Holiday Inn last night.