I've done 20-reps squats excusively for my legs for many many years. For some time I even did 2 sets, which was very tiring as you can guess. Honestly the 20-reps squat is not that effective. Gains are much slower than 5lbs/week, and sometimes quite often you don't even gain. Also it never seemed to contribute to more overall growth. But it has to be said that I am rather ectomorphic. And as for the idea of eating like a pig, definitely not a good idea, breathing squats or not. And believe me I used to squat very hard.. I've seen people a few times who apparently were doing 20 reps squats but the intensity they put into it was far lower than me. So in any case most people don't have the guts to really do them hard enough. Besides, 20-rep squats are so hard that you become obsessed with your squat all the time. It is mentally grueling to do them over a long period. And that doesn't take into account the stress on your back..