How can I tell people they are poisoning themselves?

It happens all the time- I make a new friend only to learn they are still eating seed oils, high fructose, starches, preservatives, fast food etc.

when i say something, they usually say: the price... as if eating clean is only for rich people.

if i try to explain how bad the stuff is or affordable ways to eat healthy, they get annoyed or offended. and if i try to explain how their CURRENT HEALTH PROBLEMS are a direct result of eating poison for the last 20 years, they shrug it off- because I am not a doctor or they are just too depressed to do anything about it.

Is there some clever strategy to TALK TO PEOPLE and inspire them how WORTH it they are? and how BAD the fake-foods are?