As best you can, you need to police his diet. If you live under the same roof, try to have meals with him and make sure they are always healthy meals. Do the shopping and cooking yourself if you have to. Ease healthy choices into his diet until they are the primary things he consumes.
--A glass of orange or grapefruit juice with breakfast every morning for example...
--for cereal serve Total or Product 19 (each have the 100% of the recommended daily allowance)... or oatmeal.
--make sure he gets two servings of vegetables with each meal. If you father is stubborn you may have to do all of this somewhat surreptitiously. If he claims not to like one or more fruits or vegetables find out which ones he does like and make sure they are always part of your meals. Make a small salad a part of your meals, served as an appetizer for example. Try different kinds of dressing (there are so many) until you find ones that he likes and make sure they are always in the kitchen. I hate vegetables, but my cook found a dressing I like and now, I would eat a bowl of rocks if you put my favorite dressing on it. You have to be creative and persistent.
Give him disapproving looks when he makes bad food choices... applaud and praise him when he makes good choices. Everyone responds to positive reinforcement. Again, you have to be creative and persistent.
For exercise, you need to get him in the habit of doing something like walking the dog, riding a bike, or walking around the block after dinner. Make a habit of it (join him if you have to in order to get him going).
