Bearing in mind that this is our first trip to DisneyWorld (I've been to
DisneyLand in my childhood)...I thought I'd throw my two cents in here as well.
Checking out the prices and menus, I see no reason why someone cannot afford to eat in DisneyWorld. If you are paying three hundred dollars or more to just get in to the park, surely you can budget a bit more for counter service. Or, maybe you could put the trip off for a couple months until you can afford it - or go one day less, etc.
Now, granted, we aren't doing a bunch of character meals or priority seatings, but you can get most of the kids meals for like $5 - including a drink - and the adults can get meals for around $6-8. That is *not* expensive. (And we are a family of five). It's like $65 a day!
Is there any reason why breakfast cannot be eaten at the hotel? Yogurt, juice boxes, cereal bars, bagels/cream cheese are all substantial - plus fruit is the easiest fast food.
For lunch and dinner, grab counter service. It seems like part of the magic of disney! My mom and step-dad were *very* frugal (would even steal stuff to wrap up in napkins from the Sizzler food bar to take back to hotels!!!) But, they'd always buy counter service at amusement parks. It's part of the expenses - part of the budget - part of the fun. I would have been mortified as a child to be sitting on the side eating a smashed sandwich while the other families were eating counter service. Sorry - I won't do that to my kids.
Now - ritz bits, granola bars, juice boxes, fruit snacks, little things like that to appease a small child impatiently waiting in a long line for a ride...absolutely. But, the key point is moderation. Even someone with diabetes knows what they need to eat and when...it isn't terribly difficult to plan accordingly (MIL is diabetic). She manages to eat at appropriate times when we're out shopping for the day - why would Disney be any different? And soooo many of the carts and counter service *have* healthy items on their menus. We are vegetarians and just planned accordingly by looking up the places that offered healthier options and writing them down on our itinerary. This way we can sit down and have the foods that we know we like/can eat.