Answer: Be patient with them, it's hard to break a habit once it's been in full motion, try to be firm in helping, but also listen to what the other person is feeling inside, emotional support is better than you yelling at them like a rabis having animal, Its going to take a while, dont expect them to be super healthy in 2 days, you couldn't break a habit in that time could you? Encourage them to do exercise, but don't force it on them as pressure, make sure they're going to the doctor for regular checkups if they're hazardous or not.
Explanation: Based on my personal experiences, hope it helps :)