Scientists have been working to unlock the secrets of aging for decades. But the goal is not to help humans live to 200.

The goal is to extend healthy, mobile, mentally agile years, and reduce sick years. Healthier people have fewer chronic illnesses in their younger years, and live later and longer, explains Dr. Seth Marquit, medical director at Pritikin Longevity Center + Spa in Miami. For that reason, chronic illness is the true target in the battle against aging.

It’s not just a pursuit of vanity. “It’s also about the economy,” says Dr. Brian Kennedy, researcher and CEO at the Buck Institute for Research on Aging. Health care spending accounts for about 18 percent of gross domestic product in the United States, “and it’s only going to get worse as more people get over the age of 65,” Kennedy says. “We need to solve that, and keeping them healthy is a way to do it.”

A possible upside to not eating for 16 hours
Some studies in animals have suggested that calorie restriction, meaning reducing calories while still getting enough nutrients, may extend individuals’ average lifespan and reduce their disease. Although other studies have produced mixed results, the findings have led to research on intermittent fasting, according to the National Institute on Aging.

In research, intermittent fasting means you stop eating long enough to use all the energy stored in your liver, about 16 hours or more, says Dr. Mark Mattson, senior investigator at the institute. When that happens, your body switches to using stored fat for energy, and the cells in your body experience mild stress.

Preliminary testing on humans suggests that “the neurons respond by enhancing their ability to function and start to resist the kind of stresses we think cause damage during aging,” Mattson says.

Mattson and his colleagues have been studying the effects of intermittent fasting on several diseases in humans, he says, noting that studies are in progress on breast cancer and conditions associated with dementia.

“I think you’ll see in the next year or two, and particularly the next five years, a lot of [results from studies] on intermittent fasting on human subjects with diseases or [who are] at risk for a disease,” Mattson says.

Researching medications and supplements to extend life
While many researchers focus on diet, Kennedy and others are looking for a treatment that could prevent several chronic diseases at once.

Metformin, a diabetes medication, appeared to increase lifespan in diabetic people compared with nondiabetics in one study. A newer trial is testing metformin in people age 60 or older who have one diagnosis of an aging-related illness, such as osteoporosis, heart disease or cancer, Kennedy says. Researchers will look at the time it takes to develop a second chronic illness compared with a control group.

“The idea is that a drug that slows aging is going to protect against multiple different diseases,” Kennedy says.

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His own team is looking at rapamycin, a drug used during kidney transplants that helps ensure patients don’t reject the new kidney. Rapamycin has extended the lifespan of mice in multiple trials, but it triggers toxicities and side effects in humans that make it unsuitable to take long term.

If his group could find a molecule similar to rapamycin that could extend life without the side effects, “that would be a revolution,” Kennedy says.

How to stay younger longer
With no magic pill yet available and the long-term effects of intermittent fasting still unknown, the best thing you can do to stay youthful is to stay healthy. That’s best done in the same ways we know to combat obesity: Follow a diet rich in fruits and vegetables and low in calories, and get plenty of activity.

“Exercise, by far, is the single most valuable thing you can do today to increase your lifespan,” Marquit says. He adds that proper nutrition comes in a close second: “You can’t exercise yourself out of a bad diet.”

You can also strive to reduce stress, which damages the body and contributes to aging and disease. That includes stress from something positive, such as planning a wedding or landing an exciting new job. Whenever possible, take time to de-stress and calm yourself, and get a full night’s sleep when you can.

“If we could all remain in complete calm like a Buddhist monk and experience no stress, we might live to 300,” Marquit says, “but life is full of stress, and the key is learning how to control it!”