Scientists continue to study the secrets to living a long life. While many may have their own ideas, it's clear that there's no silver bullet.

For 94-year-old Marion Downs, it comes down to attitude. Her advice: "Shut up and live!" That also happens to be the title of her book .

To hear her explain it, after 60 years of age all sorts of things happen, and complaining about it doesn't make it go away. She speaks from experience. At 89, she was diagnosed with a brain tumor. It turned out to be benign, but after surgery she really found her lust for life.

Downs, who took her first ski lesson at 50, said she recalls that she was whining to the ski instructor, "I can't do this." "Shut up and ski," the instructor replied.

It's been her philosophy ever since in everything she thinks she's too old to do. She's living longer and she thinks you can too.

Attitude is just one element of longevity. Genetics also plays a part. But even if your parents died young, that doesn't mean you will too.

Paul McGlothin and Meredith Averill took steps 15 years ago to live longer than their family members did and the science behind what they did is so statistically significant they are being studied by scientists at the Washington University Medical School.

"We're not trying to be in the Guiness Book of Records. We're just trying to live healthfully," Averill said. Researchers studying the couple have found their hearts are "functioning like people who are 15 to 20 years younger than us and our blood pressure is about the same as 10-year-olds," McGlothin explains.

Averill and McGlothin what helps is that they are "calorie restrictors."

McGlothin hasn't eaten more than 1,900 calories a day for 15 years. Averill sticks to around 1,600. They choose their foods wisely and have even written a book, "The CR Way," about how to follow their diet without feeling deprived.

Averill said although she may be tempted to "cheat," she says it's just not worth it. She said not only does she feel much better by restricting her diet to foods with "anti-inflammatory" qualities (an approach that can not only help keep arteries clear and blood flow maximized), she and Paul have even boosted their bone density something of great concern to older folks. For the elderly, low bone density can make even a simple slip and fall a fatal incident.

Downs — who spent her 93rd birthday skydiving — McGlothin and Averill make time each day to exercise, following a combination of aerobic activity and moderate weight training.

Cardiologist and FOX News contributor Dr. Isadore Rosenfeld highly recommends exercise and a reduced calorie diet for many of his patients, a fair number of which are living full lives into their 80s and 90s.

At 82, Rosenfeld is an example of how healthy living can prolong life. He works full time, has authored more than a dozen books and follows a diet, exercise and supplement ritual that doesn't look all that difficult.

"I believe that reducing caloric intake is probably the most important step toward longevity," Rosenfeld explains. Supplements aren't essential but can play an important role, he says. He cautions it is important to speak to your own doctor and believes regular checkups are important to ensuring a long life.

Rosenfeld is not alone in his recommendation of taking a low dose aspirin everyday. Many studies suggest it can be helpful to heart disease and the prevention of some cancers.

"Aspirin is a medication," Rosenfeld said.

But what about supplements?

Each day Rosenfeld takes fish oil, recommended by many doctors if you don't eat enough fish, which is rich in omegas.

"Fish oil, I can't begin to tell you how marvelous I think this is," said Rosenfeld. "It has an aspirin like effect. It tends to prevent the clotting tendency in the blood, so if you've got narrowed coronary arteries or brain arteries it keeps the blood flowing."

If you have a cardiac history or are on a statin, there is research that suggests co-enzyme Q 10 can be useful to improving your health and longevity.

Rosenfeld cites a recent study that found statin drugs, used to reduce cholesterol can deplete natural levels of the enzyme.

The supplement Resveratrol has been getting lots of publicity since a study came out that reported red wine in moderation can be good for the heart.

Although the research is fairly new, Rosenfeld himself is taking it, and for some of his patients, recommending it.

"There is a constituent in the skin of the grape which has beneficial effects," said Rosenfeld. "The latest research from Harvard is that Resveratrol contributes to longevity."

Rosenfeld said that another supplement on his kitchen counter called "Juice Plus" is good only if you are not eating enough fruits and vegetables. "The antioxidants, the various components of fruits that prevent cancer and vegetables that prevent cancer and heart attack are in these supplements," he said.

McGlothin and Averill live supplement-free, relying instead of food to provide everything they need. It's possible to eat in a way that provides everything your body needs to stay in peak form, but that can be time-consuming.

They cook their meals together, exercise together and even work in the advertising industry together.

Downs, 94, said she enjoys doing lots of things with 90-year-old boyfriend, Dick.

In several studies, scientists across the country have concluded keeping cognitive brain function alive may be as easy as making a friend. Rosenfeld said, "The key to keeping the brain active is an interpersonal relationship. Making friends with younger people and the interchange is what keeps your mind going."

And because you feel better, being loving to others is easier, McGlothin said.

"Romance as a whole, the joy of being together with someone you care about gets so much better," McGlothin said.

"That's one of the big effects of calorie restriction. We're doing Viagra without the pharmaceutical!"