“Simply put, biological age is the rate at which you’re aging physically, whereas your chronological age is simply the amount of birthdays you’ve celebrated,” says Dr. Kara Fitzgerald, a expert in epigentics and aging, and author of Younger You. “There’s nothing you can do about your chronological age, it’s always going to increase by one every year.”

There’s more flexibility with your biological age—which is both good and bad. While you might have the power to reverse it and shave a few years off of your biological age, you can also speed things up and end up feeling older than your chronological age because of poor health.

“When you go back to thinking about hypertension and diabetes and that sort of thing, people who have these diseases are aging faster than their chronological age,” says Fitzgerald. “These diseases are pushing aging forward. But also the journey of aging makes us vulnerable to getting these diseases—it’s kind of like a chicken and the egg. Ultimately, we sit in the driver’s seat of dictating how well we live by choosing how well we live.”

How to determine your biological age

To alter your biological age, first, you have to figure out what it is. While online quizzes and calculators can help you gauge your biological age, the best way to get an accurate assessment is studying your epigenetic data—or how your behaviors and environment influence your genes—using DNA collected from your saliva, blood, or other tissue.

The first reliable epigenetic clock was developed in 2013 by Steve Horvath, a researcher at the University of California, Los Angeles. His findings determined that multiple tissue types could be used to calculate a person’s biological age. 

Since then, several at-home tests have hit the market, ranging in price from $75 to $500. Of all the tests, only myDNAge is based on Horvath’s epigenetic age clock. 

Results from the at-home tests, which are most often available after two to six weeks, typically include information about your metabolic health, genetics, and other risk factors for age-related diseases. Because the tests aren’t independently evaluated, accuracy may vary across racial and ethnic groups; however, they can be a good place to start. 

What influences your biological age

Once you know your biological age, you can start to understand the risk factors in your life that might cause you to feel older. But increasingly science finds that there are ways to slow the process.

There is research that shows varying degrees of success with reverse aging: The first human study in 2019 showed biological age reversal up to three years, and another study of obese African Americans with vitamin D deficiency found participants were able to reverse their biological age by 1.85 years in 16 weeks with a supplement regimen.

“Our genes, by and large, are not our destiny,” says Fitzgerald. “Even if your parents or grandparents had certain conditions, that doesn’t need to be your fate. There are some truly powerful genetic conditions, but most of the time that’s the exception.” 

Instead, Fitzgerald insists that most of what influences our genes is our lifestyle—everything from what we eat to how much sleep we get every night.

“This is how we live, how we breathe, how we eat, what kind of stress we’re exposed to and how we deal with that stress, our community engagement, our relationships, our ability to feel love, moving our bodies … it’s all of these ways that we’ve evolved as humans,” she says. 

How to reverse your biological age

In an eight-week clinical trial, Fitzgerald and her team looked into how diet and lifestyle intervention can be used to reverse biological age. The treatment, which included diet, sleep, exercise, relaxation guidance, and supplemental probiotics and phytonutrients, was later associated with a 3.23 year decrease in biological age.

Below, Fitzgerald outlines the regimen participants followed:

1. A very specific diet consisting of a wide variety of colorful and cruciferous vegetables; low glycemic fruits; and some animal protein, particularly eggs and liver, which she describes as “a multivitamin mineral in a food matrix,” as well as foods dense in polyphenols, such as cumin, turmeric, green tea, and mushrooms
2. Adequate hydration
3. Exercise a minimum of 30 minutes a day five days a week at a perceived exertion of 60-80% of one’s maximum
4. Regular meditation, breathing exercises or other relaxation practices
5. At least seven hours of sleep per night
6. Two supplements: extra polyphenols, in this case, a greens powder, and a simple probiotic

“Every piece in our intervention was designed based on what favorably influenced DNA methylation [how methyl groups interact with our DNA] and epigenetics,” says Fitzgerald. “The whole program was built brick by brick to sweet talk gene expression and turn off bad genes, like genes associated with cancer or even inflammation, and turn on good ones.”

The best time to start implementing diet and lifestyle changes to impact your biological age is in your 30s as changes in the aging journey really “kick in” during our 40s, she says. 

“The sooner we’re getting in there with the information to counter the negative changes associated with aging, I suspect the better outcome we’re going to have,” says Fitzgerald. 

“Aging is the biggest risk factor for chronic diseases and even acute ones, such as COVID or influenza. If we rally our resources towards cracking the aging nut toward slowing and even reversing biological age, the possibility for humanity is just extraordinary.”

Editor’s note: This story has been updated to amend some earlier factual errors.