MWMom,
kt has some weight issues & a budding eating disorder. We don't use the word diet ever. I really push healthy eating choices.
kt's therapist is teaching kt about portion control. 5 ritz crackers = one serving. 6 midget tootsie rolls = one serving. kt is beginning to watch & ask what a portion serving is on her snack. She is also beginning to choose yogurt along with graham cracker sticks as a snack.
All this has taken at least 7 months. She knows that if she makes herself throw up, her priviledge of choosing foods is gone for at least a week. (I know this doesn't apply to Lucas.)
I don't know if Lucas will grasp the idea of healthy life & choices. I can't remember if Lucas is big on riding his bike or skate boarding - a physical activity. For kt & her scooter, we used the fact that the healthy choices she makes will fuel her body to ride her scooter or go swimming. Other less healthy foods will not help her do some of her favorite things efficiently.
Again, I can't say if this will work for Lucas. However, I wouldn't focus on his appearance or his portions at this point. I'd just spend this time teaching him what the healthy choices in food are & what portion of those foods make up a serving. Keep out a big bowl of popcorn (with-o butter, lightly salted), a bowl of whatever sweet fruit that is Lucas's favorite (kt loves grapes). I keep kt's favorite yogurt on hand, along with cheese sticks & graham cracker sticks.
Good luck with this.