I taught diet changes for years to heart patients, but always knew they'd be tripped up by family, friends, and their culture. Eating and sharing food is a large part of who we are, and we're not always in control of the menu.
People who were already looking at a shortened lifespan largely due to diet and lifestyle things like smoking knew they needed to change and they knew why they needed to change, they just couldn't manage doing it and we'd start to see them as revolving door patients, bouncing back and forth between home and hospital, a little sicker every time.
We really do need to do a better job of this sort of thing, probably starting in the schools with adult education in the evenings teaching basic cooking so that people can take control away from food processors and their high fat, heavily salted and sugared products and move them back toward the things people ate 100 years ago that didn't plaster their arteries with trans fats or overtax their kidneys with salt and preservatives.
I don't know what else the answer could be, but just telling people why they need to change isn't going to do it for them. They pretty much already know that. They just can't manage figuring out how to do it. Being guilted by guys like Maher just make them reach for another beer and that bag of chips so they can feel better for a few minutes.
(I couldn't lose an ounce the whole 24 years I was on Prednisone. I've lost over 50 pounds since I went off it. Fat is not always our fault)