Is there any benefits in doing cardio? When people wake up in the morning and do cardio before breakfast, it eats away at your muscles. Thats awful. People do cardio after weights for an hour 5 times a week. Why? Cardio only burns extra calories. And if your in a calorie deficet when you do the cardio, it burns muscle, right? I know it sounds somewhat lazy, but why don't people just cut calories from theyre daily diet instead of risking catabolism. Just one glance at one of those "under-nourished" proffesional marathon runners with bones sticking out makes me want to vomit. The only point I see in doing cardio is if you had a brownie sundae from Dairy Queen and you were on a cutting diet, so you run a mile or so to burn it off. Thats the only point I see in cardio, is there any health benefits?