Here's your response::
Him: you should eat every 2 1/2 hours.
You:
Ya, you know you're probably right...
(keep right on doing what you are doing)
Him: you think too much about food.
You:
Ya, it's CRAZY isn't it!! (keep on doing what you are doing)
Him: you should stop thinking about food so much.
You:
Ya, you know, you're probably right (keep right on doing what you are doing)
Don't engage him in arguments. Don't defend your choices. Don't explain what you are doing. Just agree, and keep on your path. And think "poor thing, it's the best he can do" and KEEP. ON. YOUR. PATH.
In a few months, he'll see. But for now, he wants to control the situation. While he can butt in, he can't make you conform! The key is to agree with him thus deflating the situation, and then just carry on with what you are doing!
This really works -- the amount of advice I got about what I should or shouldn't do at the beginning was STAGGERING. I just did the above and kept on my path, and I'm not doing so badly. NOW those people with the advice tend to ask ME about how I've done it...
Kira