This is what Junichi Masuda said during an interview with Game Informer:
"There’s a lot of fruits and vegetables in the world of Pokémon. There is also a variety of snacks and various candies and whatnot that come from the different regions. The Pokémon world is much more technologically advanced than the world of our own, so perhaps there is probably a lot of different food that we can’t even think of.
One example of that is there is even a Rare candy which is an actual snack or piece of candy that can make you stronger, raise your level. There are all kinds of strange food that really doesn’t exist in our universe."