My 15 mo eats a ton too (at least to me, it seems like a lot because DD1 has always eaten like a bird).
We have observed that whenever anyone sits down with food (even if she has just eaten) , she comes over and immediately starts to make demands. My DH says she is like the Mafia coming around to get her "cut". I have realized that a lot of her eating has nothing to do with being hungry, and more to do with modeling and mimicking us. She is not really hungry, she just wants to do what we are doing (rarely though, does she turn down anything that is offered).
Just another factor to consider. But, I agree with lots of the other PP's about adding more table food, particularly proteins and carbs is likely to 'fill her up' more.