How about a dose of realism here, folks. If you are getting this deal FREE, like the OP, then that's fine. Or if you have a lot of discipline, and plan to do, say, two dinners and a breakfast, and call it enough.
But with most people, they "want to get their money's worth," so they will try to do as many meals as possible, and eat as much as possible (I suppose that is why one poster mentioned bringing antacids). That's a lot of food! If you can eat a regular breakfast, and either no lunch (and an early dinner) or a small lunch and a dinner, that would work. But eat it all, just because it is there, yuck. Are you the same people who are complaining about airplane seats?
Choose wisely, my friends. Go to the best buffets, and remember that quality always trumps quantity.
YMMV, and JMHO, of course.
Fern
BTW, if you don't do the buffet ticket, you can enter the Rio between 10:30AM and 10:40AM and be able to eat both breakfast and lunch. Lunch begins at 11 AM (and includes sushi), and some days they stop entrance from 10:45AM to 11 AM. Some days they don't.