Normal coke is full of sugar which will make you fat.
Diet coke is even worse because all that caffeine will give you adrenal fatigue, shrink the muscle's you do have and deposit it as fat on your mid section.
I hope you are pissed off, enough about this to quit coke.
I see the future in my house. My wife standing in the kitchen with a new juicer of some kind. Me, drinking liquid beets.
Your right of course about quitting. I quit smoking and drinking. Quitting something hardwired into my brain and body through a couple million years of evolution should be easy by comparison.
If you can quit smoking, coke should be easy.