"I have male and female patients in their 60s and 70s who are still wildly active," said Huntington Hospital's Dr. John de Beixedon.
And doctors say those are the patients who appear the most youthful.
"I think there's a cascade of effects that's associated with hormone release that can certainly keep your brain operating, amongst other things," said Dr. Amin Mirhadi, Cedars-Sinai Medical Center.
People who feel virile in their 70s and 80s are also the ones who've spent most of their lives being active. A new study shows researchers can calculate how much longer an elderly person will live based on how fast they walk. Spry walkers usually exercise with consistency.
Dr. Mirhadi says exercise releases an important enzyme called lipoprotein lipase.
"What that does is that breaks up fat and makes it more readily available for fuel, as opposed to it going into storage in your belly and other places," said Mirhadi.
And what's the best diet for living longer? Experts say it has little to do with eating vegan, low fat, low carb or high protein. It's all about getting a little of everything so you have a balance of nutrients. And moderation.
"In animal species, animals that are underfed live longer and guess what? In humans, same thing: People who eat less live longer," said de Beixedon.
Another key to longevity: your social network. Not only do friends help you de-stress because they're someone to talk to, friends can keep you engaged, motivated and excited about living.
"Sharing your thoughts, sharing your feelings, and that can tend to release endorphins and make you feel overall better about yourself," said Mirhadi.
Mirhadi says the happiest and healthiest seniors he knows are the ones who love their jobs so much that they're still doing it. So he feels one of the best secrets to feeling good well into your 70s and 80s is to keep challenging yourself.