If I ever go to Switzerland, you will have to draw me a map of where NOT to go.
Sure, there are always places that are outrageous. But coming back to the issue. 90 pounds sounds like enough, but for a high performance athlete, it may be borderline. After a 4 hour battle, one roll of sushi is certainly not enough fuel to put back in the tank. I am also sure that top notch athletes do not eat like us: they do not have three meals a day; most likely, three full meals, and a series of high power snacks throughout.
I remember Michael Phelps once showing what his breakfast was. It was around 12,000 Cals, because he needed to pack that much for a full day in the pool.
I am sure Novak eats a lot of "special" food. Rafa too. You don't get that level of fitness with a bowl of corn-flakes in the morning.