Some anime cons post or print in their con booklets that attendees should eat at least two good meals during the time they are attending to keep up their energy during the con.
I usually eat a breakfast say in the hotel where I am staying and then eat dinner say Subway or convention center eatery as long as its something that will meet the need for the medication I have to take.
I will take backup snacks and drinks that I keep in the room in case I don't get to eat a regular meal.
Now I stand 5'8" and weigh 160 to 165 lb.
My friend I attend one con with stands 5'8" and weighs close to 200 lbs.
The most I have ever seen him eat or drink at a con is a large bag of M&Ms and a 12 pack of Diet Pepsis warm. He will drink a Pepsi gobble M&Ms when he wakes up pack a few in his backpack. When he returns to the room drinks two Pepsis and gobbles M&Ms before bed.
Another friend at another con will bring V8 and fruit drinks and energy bars. Some hotels we stayed in only served breakfast and meals were either from fast food, restuarants carryouts, convention center eatry or provided by con staff for staff volunteers.
This friend is 5 foot and maybe weighs around 130lb.
I worry about the other friend because I know they eat better than that at home than at a con I would hope.