The biggest: drink water instead of the sodas and sweet drinks.
Do lots of walking at WDW, so it won't matter so much.
Eat when you're hungry ie. snacking has a place and the choices at WDW
Fried is the last way to have something cooked, but on vacation treat yourself. I've come up with a rule: I love french fries, but if they aren't so good I simply won't eat them. I cannot afford to waste those bad calories on bad fries. Sent some back today and actually the steamed veggies I got were really good.
Enjoy the simple and fabulous desserts and snacks. Simple: Mickey bar, you could choose those fruit bars, but I can only get a Mickey bar at WDW and won't deny that simple treat a few times during my stay.
One not six. I got one pretzel doctored up the way I wanted at Goofy's. Didin't have another while there, but over the course of a couple of days loved that one. I'm a bit weird, I can nurse a pack of M&Ms for a week.
If you chose to share desserts get one decadent and sorbet or fruit for the other. Another trick I used twice, I had a kids dessert, great taste, simple recipe smaller portion.
We shared a pizza combo meal. I ate the side salad and our 6yo was ridiculously happy to "tear up" the pizza. I was surprised at the freshness and flavor of the side salad. I didn't even bother to add dressing and it was filling. Left me more room for that packaged carrot cake. I downed it all with water from the fountain machine. That water is filtered, similar to the Dasani water.
Florida is still known for fruit, so eat that if it grabs you too.
We did serveral buffets so you can make repeated healthy choices and grab a taste of those "I really shouldn't" items. So you get to be bad, but not too bad.