M.K.
I've got an incredible eater too! My daughter is 26 months old and will eat an ENTIRE foot-long hotdog from Costco! (She's done this twice!) She has always been an excellent eater (eats ALL veggies, including broccoli and brussel sprouts) and we feed her healthy food at home. (Well..okay, I let her have mac-and-cheese about once every two weeks.)
Since her three month well check-up, we have asked the Pediatrician, "Are you sure her weight is okay?" "Is she eating too much?" And once she began eating table food exclusively, "How much should she eat? Should we limit her food?" We always were told, "Oh, she's just fine...let her eat as much as she wants. She'll stop eating when she's full." Then, at her 2 year appt, the Pediatrician OUT OF BLUE said, "We need to start getting her weight closer to the percentage of her height." My husband and I looked at each other and almost laughed! That's what we've been worried about all along!!
I'm sure you are doing the same things I am -- absolutely no treats until good servings of veggies, proteins and healthy carbs have been consumed. And we don't give treats more than twice a week (a sugar cookie, animal crackers, etc.)
My daughter is not fat, but her weight has always been in the 90-95% while her height has always been around 80%. So...I'm cutting her fruit off after a 1/2 cup serving at the end of her meal. If she says she's still hungry, I offer her more carrots. Sometimes she takes more carrots!
So...I don't really have any advice for you at all! But I wanted you to know that you are not alone!!