That isn't really how microwaves work. Or, perhaps, that's how all radiation heat things work. It's any molecule that will absorb radiation of that frequency. So your grill works the same way, just at a different frequency. At microwave level, it's water, fats, all sorts of things. The difference is really the stuff that doesn't absorb at those frequencies.
That’s a bold claim. How did you come to this conclusion? Do you have any scientific literature you can point us to that proves microwaved food is unhealthy?