The following will require a great deal of discipline and perseverance, but I have done this for many years and unlike most of my age cohort, I'm quite healthy and not even pre-diabetic.

Hit the gym or do some vigorous exercise 5 days a week. Aerobics and weight lifting. Start light, and gradually work your way up to longer aerobic exercises and greater weights. I row for aerobics, 20 minutes a day, and get my heart rate up for that prolonged, uninterrupted length of time. It improves heart function. Weight lifting improves bones, muscles, and joints... but again, start low and work up to heavier weights over time. Allow two days per week off to let your body recuperate.

Eat right -- start eating more salads, fish and meat are OK in moderation, and GREATLY reduce sugar intake (or eliminate it if possible) and processed foods. Shop around the perimeter of the store where produce and the more healthy foods are.

I haven't had any alcohol for 36 years now, and my life is incredibly better. Smoking is completely out, and I never did it.

In my experience, very very few people ever follow this advice, and it takes a lot of discipline to stick with it. But hey, we're just talking about living longer and healthier, so it's up to your friend.

My doctor tells me that I am his healthiest patient, especially considering my age. So this pays off.