Hi.
Young children can't control much... but they can control what they eat. if your child sees you are concerned about his eating, he may pick up on it and it may become an issue.
If he is falling asleep before his evening meal, could you make it earlier?
My youngest used to sometimes not eat certain meals... or fall asleep before tea. If she were my eldest I would have worried... but she did eat on average one good meal a day.. and she ate fairly healthy stuff and she wasn't hungry. I didn't panic as she was developing well and she now eats fairly well (although doesn't like much meat!).
I', sure Hemyola's right...he'll be eating well very soon.