I still think you should have the blunt conversation with him, but perhaps use that as an opening to "let me help you manage this process" and pick one or two c

I still think you should have the blunt conversation with him, but perhaps use that as an opening to "let me help you manage this process" and pick one or two changes to start with. Too much change at once == massive resistance. Small changes may seem like they don't have much impact, can build up over time. Can you take a 30 minute walk with him every day? Every couple of days?