My son is a very poor eater, too. Also 2, but always been over 100th centile so I've never been taken seriously. His appetite is appalling.
His diet is pretty much porridge, toast, beans, rice, pizza, breadsticks, crackers, wraps, fruit pouches.
We had our long awaited appointment with the dietician yesterday and everything she told us to do, we're basically already doing.
With DS, the comments of "he'll eat if he's hungry" just weren't true. He would allow himself to go hungry. You could hear his tummy rumbling.
The advice from the dietician was:
Offer him his safe foods for a minimum of 2 meals and 2 snack times a day. That way if he doesn't eat his third meal or third snack, I know he's not going hungry.
If you're financially not able to offer meals we know he won't eat, then ensure he's exposed to new foods through what we eat, I.e. let him see us eat foods that he doesn't, and if he tries it, gives lots of positive praise. If he doesn't try it, don't acknowledge it or give it any attention. She said him just licking the food, even if he doesn't try it, should be given positive praise.
Give a multivitamin for whatever he is missing out on.
That was basically it. There was really much more to say than that.
Like you've said, it's not just the hunger that's the concern, but the health implications it can cause. He's now been referred for blood tests to check his iron level as she's concerned about that, due to lack of natural sources in his diet.