Dear Ms. Thessin,
No, your son's behavior does not sound like incipient eating
disorderAdjustment disorder
Anorexia nervosa
Asperger syndrome
Autism
Autoimmune disorders
Bipolar disorder
Bipolar disorder
Bleeding disorders
Borderline personality disorder
Bulimia
Chronic motor tic disorder. The pediatrician's advice is very wise; you won't be making a mistake if you take it to heart.
One adjustment you might make is around the types of food you have in the house. Perhaps you abet his habits a bit by making too many of the desired (but not particularly nutritious) foods available.
Try not to think about this in terms of winning/losing. It's not a contest. Simply prepare sensible meals, offer them to him, and let nature take its course. He'll be OK.