Totally feel you on the desire to help your parents take better care of themselves. Both my parents are much further along the aging process than they ought to be; my dad is 67 and in a memory unit. My mom is in bad shape as well.
The main thing I’ve found from trying to help them be healthier: trying to change other people is generally a recipe for increasing your own stress without accomplishing much else.
Instead of trying to change them, I’ve been focusing on trying to enjoy what time I have left with them. It’s bittersweet for sure, but I’m finding that knowing where this is all going accentuates the sweetness of being able to love my parents while they are still around.
Best of luck to you and yours.