J.D.
I know some will think this is harsh but I had a picky eater once also. I cooked a healthy meal on the first night and he refused to eat it. So that night he went without. (He will not starve in one night.) SO the next night I made a healthy meal again. He whined a lot and picked at it, but ate some. The following night Same healthy stuff. He complained a little bit but ate most of it. There was no candy junk food or anything for a week. He had no choice but to eat the good food. Within a week there was no more whining and picking at dinner. Within a month of barely any sweets or junk food, he started to ask for the healthy things. I had to get it in my head that I am the parent and I am setting the example. He can't eat the junk if I don't offer or give into him. Unless he is allergic to something I don't think he should have to much trouble adjusting to a NEW way to eat. Good luck.