What one longevity researcher is doing in hopes of living beyond 100

Valter Longo is currently in his mid-50s, but he hopes to live another 60 to 70 years.

Longo is a professor of gerontology and director of the Longevity Institute at the University of Southern California.

He is also the author of "The Longevity Diet" and the creator of what he calls the fasting-mimicking diet, or FMD, an approach to eating that he believes could be a key to his goal of living to the age of at least 120.

Ultimately, Longo acknowledges how difficult it will be to reach even 100 years old, however he remains optimistic that his research will help him get closer.

"I would say the connection to longevity is an obsession," Longo told "Good Morning America," adding that he started studying genes and longevity at age 18, and now focuses on nutrition as the key to a long life.

Longo described FMD as a short-term, low-calorie diet that is designed to mimic fasting.

The diet is designed to be done five days in a row, three times per year, for a total of 15 days per year.

On the remaining days of the year when a person is not following FMD, Longo said he eats during specified periods of the day.

"I always recommend 12 hours of fasting, and 12 hours of feeding, so say 8 a.m., to 8 p.m., that's very important," Longo said, noting that he believes 12 hours of not eating is the safest approach to fasting.

Intermittent fasting, or time-restricted feeding, is where you limit the times during which you eat, typically only in an eight-hour time period.

Research shows that intermittent fasting may help decrease cholesterol, decrease insulin in the blood, results in some weight loss and reduces inflammatory markers for some. But it is not the only way to achieve better markers.

A study published in the journal Cell Metabolism in 2015 reported that a fasting-mimicking diet reduced the markers and risks of aging in mice. A trial of the fasting-mimicking diet was done in people, and analyzed this year by Longo at USC.

As with any new medical discovery, there are limited studies to confirm that any specific diet can guarantee a longer life.

"Although the studies are promising, by most standards, a lot of these studies are limited," said Dr. Darien Sutton, ABC Medical Contributor, adding that people should always "have caution" when they see a straightforward answer to a multi-faceted problem.

Studies thus far suggest that avoiding ultra-processed foods, staying active and maintaining a diverse, balanced diet help prevent diseases long-term and thus prevent likelihood of premature death.

For those hoping to live longer, it's important to focus on risk factors that are in your control. For example, heart disease is the number one cause of premature death in the United States, according to the Centers for Disease Control and Prevention.

"How do you reduce those risks? You're avoiding ultra processed foods, you're staying active, you're maintaining a balanced diet, avoiding too much added sugar and most importantly, getting the appropriate amount of sleep," Sutton said. "These are the key ways that we know are tested and true in order to live healthier and live longer."

Longo said he also eats a modified version of the Mediterranean diet, which is associated with a longer lifespan. The diet is rich in complex carbs, good fats and lean proteins.

"It should be a vegetable-rich diet with most of the proteins coming from vegetable sources," Longo said. "And there should be a mix ... so legumes should be accompanied by nuts and by seeds ... and whole grains, the whole grain cereals, those are the ones that are ideal."

Longo also suggests varying the type of fish you're consuming too, saying, "It's best to limit the high mercury fish, like swordfish and tuna, and focus on the small fish that have less mercury, but also rotate between different types of seafood and fish."

While promising, any of these dietary changes come with risks to your health, and people should always talk with their healthcare provider before making any changes to their diet.