What should I do about my parents?

Ok so my parents are saying how they are going on diets. Perfectly fine, so I suggest to them to get rid of all the junk food we have. They say no and get mad. They keep buying soda and I tell them they can't have that they just reply "yeah." so every time I make dinner I always grill the meats or bake them and make vegetables. Today I make broiled chicken and my dad gets mad at me... Really I'm quite aggravated. I don't know what to tell them anymore. Any suggestions?