Normally during training I think so. But during tournaments overseas, it is a bit difficult, you often see players eating in local restaurants or hotels. I think they just eat anything, as long as they eat sensibly and don't over do it. Sometimes you hear players have food poisoning, or diarrhea Obviously most Asian players favor Asian food, usually settling for Oriental food. Check out the WC05 pictures thread. I have even seen some players buy burger and fries from the hamburger stand here!
In talking to Sony Dwi Kuncoro during WC, I learned that the Indonesian team had Indonesian food catered for them everyday, but the players did get a per diem that they can use to buy additional food on their own. As Chris' photos show, the team went to eat at a Thai restaurant for a welcome dinner. While some players may stick to their "native food" so as not to upset their stomach, some others may just eat about anything. Like Lilyana Natsir -- photos from WC showed her eating Thai on Sunday, Korean food on Monday, and Chinese food (with Chinese players) on Tuesday. On Thursday I saw her buying Carl's Jr burgers at the Anaheim pond. All that, and she got WC gold in mixed doubles!! So, there's obviously no correlation between special diets and performance!
Asian players eat more carbohydrates and this is ideal when coming into a tournament. Some may even do carbohydrate-loading to prepare themselves for extended round after round of tough battles. Eating bananas or drinking fluid with glucose extends your stamina quicker than complex carbohydrates which are low glycemic. During games you need 'speedy' glucose from simple carbohydrates like glucose, sugar, pocari sweat, etc. The only fuel for your muscles is glucose. Protein and fat will give you none and will probably stop you from going anywhere, even the first round. I am sure the top European players who eat more protein and fat than their Asian counterparts will switch to a high carbohydrate diet when preparing for tournaments.
