It's really difficult. I have to bite my tongue so I don't start a huge debate when my friends talk about low fat dieting, trianing for marathons and watching the Dr. Oz show. My dad always appears to know everything about the human body but his diet is so inconsistent. You can try to tell them but they have to be willing to make a lifestyle change which is hard to do. Some people don't really make the jump until something really goes wrong like auto-immune issues, or weight gain that doesn't stop even with tons of exercise.