Pre and Post-Surgery Food Plans for Traditional Central American Palate

I've a pre-surgery patient who has recently moved to the US and is struggling with the meal plans that are not what the patient is accustomed to eating. At home in Honduras, he says that they are told to eat the same food as they always have just in smaller amounts. There is not the strong emphasis on protein, and reduced carbs. Rice and beans are a big part of his diet now. How have others adjusted their pre and post surgery diets who have a more traditional Central American way of eating? Any one have guidance?

If he is successful with his diet right now - why change anything? Just because another country has other guidelines doesn't mean they are better guidelines.