Trying to get my Dad healthy

I have been  active for my entire life, from sports in High school, to having to maintain a high level of functional fitness for work. My Dad was about 140 lbs of pure lightning up until he became an adult. For some reason, like so many others, growing up meant getting fat and stiff. He is now 61, and tips the scale at 220 standing 67 inches tall. He also drinks about a gallon of sweet tea PER DAY. I have tried many angles, from hanging up pictures of his youthful 6 pack self to guilt him, or bluntly telling him he is on the fast track to arthritis and early death. I just want him to be able to play with his grandkids for longer than a minute without having a heart attack. Does anyone have any success at dealing with this issue? Any advice is appreciated!