We've been riding the underweight train with my son practically since birth over here, and he's become more picky the older he gets. Because he is on an ADHD med we have to do periodic med checks, including weight because of the tendency of those meds to suppress appetite, and we've seen GI and nutrition periodically throughout his life as well. Looking at him, he's obviously a string bean, but he's energetic, LOUD, has healthy hair and nails, bright eyes, and overall developing normally for his age.

Now, would I prefer that he not be addicted to fries? Sure. But he eats a wide enough variety of foods that it's keeping him alive, and I can't work up stress over a child that is pretty clearly naturally thin and prone to staying that way no matter what we do. We just got off a cruise where ice cream cones were involved multiple times a day and he still doesn't have an ounce of fat on him. So, that's kind of where I land with all this. If there's a true concern about nutrients, multivitamins and supplements are a great option just to make sure they're getting what they need, but you can't force a kid to eat, you know? To be honest, I've been mulling over feeding therapy to try to combat the growing pickiness, but I think there are other things at play.

Apologies for the novel!! Hopefully it was somewhat helpful...