Sounds like a food fight. I'm familiar with food fights.
Does he see a doctor regularly? Does he have high blood pressure? High cholesterol? Fatty liver? High blood sugar? No? Then he doesn't have a reason YET to eat like you do, so don't make him.
It sounds like you have been gaining weight living in this household. Is it really so awful to cook your own meal to fit your own diet? If you do that, would it be a problem for HIM? How could it possibly be a problem for you? You will only improve your health and lose the weight you want. His health will stay the same, which is probably fine with him! If his health starts to show signs of any problems, then he can make the decision himself to eat your food.
But what about mealtimes? You both sit down at the table and eat your own foods. You spend time eating together, just not eating the same things. He can eat fast food or he can eat your food. It's up to him.