Unlike most men his age, David starts every morning with 60 minutes of cardio and weight training.
"How many 85-year-olds do you know that can do 50 push-ups without a break?" Oprah says.
Watch Oprah's visit with David.
Then, it's time for breakfast. David says the real secret to his vitality is what he eats. "I try to eat fruits and vegetables exclusively," he says. "I never eat any saturated fats."
David doesn't restrict his calories, but he does choose his meals wisely. He says he usually eats natural oatmeal for breakfast, an egg white omelet packed with veggies for lunch and a nice piece of fish with more veggies for dinner.
Three or four times a day, David treats himself to a special smoothie made with 15 different fruits and vegetables. Thanks to all the spinach, carrots, mangoes, grapes and other ingredients, David says he hasn't had a cold or the flu in 20 years.