Although it is difficult to narrow down the best of the caloric intake options Rio has to offer, the following will prove most excellent in your conquest of hunger:
PORCÃO | For those who do not know, a churrascaria is a magical place where you may sit and gorge yourself on a delicious buffet of salad, sushi, fruit, rice, beans, and a multitude of authentic Brazilian dishes for a (usually) modest price. Oh, and for the main event you'll receive infinity meat served up directly to your table and hot off the grill (everything from chicken heart to filet mignon). Porcão (big pig) is one the the most well know (and delicious) in Rio. With multiple locations throughout the city it will be difficult to miss this place.
Cost: ~R$70/plate (drinks and desert extra)
FORNALHA | When you find yourself wandering the streets of Copacabana late at night, eyes glazed from one too many cachaça shots, ears echoing music from the club, and you suddenly find yourself craving solace in some delicious goodness: Fornalha is your answer. Open 24 hours (with multiple locations), this gem serves up cakes, beverages, and best of all salgados (magically delicious combinations of breaded/fried cheese and meat). You may regret the combination of DADS and salgados come the morning, but trust me, the short-term satisfaction outweighs the long-term consequences every time.
Cost: ~R$3/snack (and you can't eat just one)
RODIZIO DE PIZZA | If unlimited meat isn't your thing then how about unlimited pizza? At a rodizio de pizza you will be the joyous recipient of all manners of traditional pizzas and “desert pizzas”. Cheese, pepperoni, sausage, bacon, onions, chocolate strawberry, banana, white chocolate, and anything else you can dream up will be served to your table for as long as you can stuff your face for. The dishes come at you quickly, so remember to take it easy and pace yourself, that pizza will make another round later on.
Cost: ~R$35/plate (drinks not included)
SUCO JOINTS | Serving up freshly squeezed juices of all varieties (really, anything you can imagine), delicious bowls of açaí, salgados, sandwiches and more, suco (juice) joints dot the corners of Rio de Janeiro streets like gas stations. You can often find two or more at the same intersection offering you similar, yet slightly unique options to satiate your snackage needs. Perfect for a small meal or a quick bite to eat, you may find yourself frequenting suco joints more often than you would expect. Bibi Sucos in Leblon might be my favorite.
Cost: ~R$3-15 per item
ON THE BEACH | One of the luxuries you will find in Rio de Janeiro is the excellent service provided to its beach goers. Sure it may be annoying having to tell someone every other minute that you are not interested in their jewelry or their cangas (really, don't buy things other than food on the beach, they are very overpriced (the food is too, but its worth it)), but that moment you find yourself wanting a nice cold beer, a water-filled coconut, or some fried cheese on a stick, you will be grateful that you have these hardworking vendors at your disposal. Just beware of the shrimp skewers, I never did trust those guys.
Cost: ~R$3-7 per item