Maybe you should find a new doctor who will be more attentive. If your food is going right through you, you won't be getting enough nutrition.
I don't remember the site, but I did read on a website some tips after colon surgery:
Eat smaller meals, eat more often (like 4-6 small meals a day).
Avoid foods that are related to gas
Try not to drink after you eat, that pushes stuff through faster.
I've adjusted what I eat and when, and when I work (I teach and try to teach in the morning because my bowels tend to move after lunch!).