14 Ways to Age in Reverse

The answer is more complicated than counting the number of candles you blew out on your last birthday cake. Your daily habits can either add or subtract years from your life—like how much you exercise, or how stressed you allow yourself to be. Read on for 14 things you can start doing today to live a longer, healthier life.

Being obese increases the risk of diabetes, cancer and heart disease, possibly shaving up to 12 years off your life, per an analysis in the journal Obesity. But being too thin can hike your risk of osteoporosis and poor immune function. So aim to stay at a weight that's healthy for you.

Regularly exceeding one drink a day or three in one sitting can damage organs, weaken the immune system and increase the risk of some cancers.

Related:How Alcohol Affects Your Body

Chronic stress makes us feel old—and actually ages us: In a 2012 study, Austrian researchers found that work-related tension harms DNA in our cells, speeding up the shortening of telomeres—which protect the ends of our chromosomes and which may indicate our life expectancy. Of course, it's impossible to completely obliterate stress. "What's important is how you manage it," says Thomas Perls, MD, associate professor at Boston University school of Medicine and creator of the Living to 100 Life Expectancy Calculator. Practice yoga, pray, meditate, relax in the shower or do whatever else chills you out.

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Having more education lengthens your life span, according to a study in the journal Health Affairs, for a number of reasons. Extra schooling may help you become better informed about how to live a healthy life. And educated folks, as a group, have a higher income, which means greater access to good health care and insurance.

More and more research points to the value of having friends, and not just on Facebook. An Oxford University study found that being married makes you less likely to die of heart disease, which researchers suggest may be due to partners encouraging the other to seek early medical treatment. Same goes for friendships: Australian research showed that people with the most buddies lived 22 percent longer than those with the smallest circle. "Having positive, meaningful, intimate relationships is critical to most people's well-being," says Linda Fried, MD, dean of Columbia University's Mailman School of Public Health.

Volunteering is linked to a lower risk of death, a University of Michigan study suggests. But you don't have to log hours at a soup kitchen: Simply helping friends and family—say, by tutoring your niece or assisting your neighbor with her groceries—lowers blood pressure, according to researchers at the University of Tennessee and Johns Hopkins University.

Exercising regularly—ideally at least three days of cardio and two days of strength training a week—may help slow the aging process, Canadian doctors reported. "Being physically active is like keeping the car engine tuned," Dr. Fried says. "Even if there's decline with age, it's less severe." You were never an athlete? Don't worry: Starting to work out now can reduce your likelihood of becoming ill going forward, a 2014 study suggests.

A diet rich in processed meat—including hot dogs, sausage, cured bacon and cured deli meats—has been linked to a higher risk of heart disease, diabetes and colon cancer. Limit your intake as much as possible.

Lighting up increases your risk of not only lung cancer but also heart disease and cancer of almost every other organ. "Just one cigarette a day can take 15 years off your life," Dr. Perls says. Though you won't instantly revert to pre-smoking health, kicking butts will cut your added cardiovascular risk in half after a year and to that of a nonsmoker after 15.

Related:15 Ways Smoking Ruins Your Looks

Good news for java lovers: Research indicates that drinking it regularly may protect against diabetes, cirrhosis and liver cancer. And Harvard research suggests that drinking 3 1/2 cups a day may lower risk of heart disease. Read more about the health benefits of coffee.

For evidence that you can—and should—make slumber a priority, look no further than a 2013 study from the University of Surrey in England, which compared a group who got less than six hours of sleep a night with a group who got 8 1/2 hours. After just one week, snoozing less had altered the expression of 711 genes, including ones involved in metabolism, inflammation and immunity, which may raise the risk of conditions from heart disease to obesity.

The feel-good rush you get from it helps you fight stress and depression, jolt the immune system and lower blood pressure.

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In a 2013 Annals of Internal Medicine study, women who followed a Mediterranean-style diet were 40 percent more likely to live past 70 without major chronic illness than those with less healthy diets. Eat lots of veggies, fruit, fish and whole grains, and avoid simple carbs, such as pasta and sugar ("age accelerators," Dr. Perls calls them). Try these Mediterranean diet recipes.

Have one or more relatives who lived into their 90s? You may be genetically blessed. But that doesn't mean you should quit the gym and live on doughnuts. "Before you get to extreme ages, healthy lifestyle is more critical than genes," Dr. Perls says. So thank your ancestors, but stick to vegetables and cardio as life insurance.