Yeah, my son is now two and just RECENTLY began to have an appetite.
Also he started daycare, so that probably has a hand in it also.
Weight wise my son is below the 10th percentile for his weight in comparison to his height on the charts. But besides his weight, he is a happy active child, that happens to be on the slim side. He always managed also produce stool and urine too no matter how little he ate.
Actually he has his 2nd gastric appt in two weeks, he had his first many months ago.
My son got a blood test and it tested positive for celiac, but he didn't have high enough gluten counts to have celiac disease (confusing). Its kinda like a sensitivity/allergy to gluten. share this with your pediatrician. Ask if you can get a blood test for celiac disease. There's a lot of resources online for the disease and its symptoms. Do a google search. Or it could just be the standard "picky eater".
Good Luck.