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• When it comes to your age, there are two numbers. There’s your chronological age, which is how many birthdays you’ve had. There’s also your biological age — how old your body appears to be, based on how it functions and how much wear and tear your cells have gone through.
• You can’t change your chronological age, but you can do a lot to reverse your biological age. With the right tools, you can have the body and brain of a 25-year-old, even when you’re pushing 50.
• This article teaches you how to reverse your biological clock by upgrading your mitochondria, turning on autophagy, and managing stress to keep your cells young and healthy.

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How old are you?

Researchers are discovering that there are actually two answers to that question. The obvious one is your chronological age: the number of birthdays you’ve had. But there’s also your biological age. Your biological age is how old your body appears to be — how well your organs, hormones, muscles, and brain work, and how much wear and tear your cells have gone through.

In the last few years, researchers have developed tests that figure out biological age[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/28396265″]. They’ve also discovered that your biological age is a much better predictor of longevity than your chronological age[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5865564/”][ref url=”https://www.ncbi.nlm.nih.gov/pubmed/28958059″] 

If you take great care of yourself, it’s possible to be 50 years old chronologically with a 30-year-old biological age. Conversely, if you eat junk and neglect your body, you can have a 50-year-old biological age when you hit your 30th birthday.

With the right tools, you can change your biological age to make your body younger, and you can do it more quickly than you might think.  

In his recent Bulletproof Radio podcast episode [iTunes], anti-aging expert and investor James Peyer talks about the many things you can do to reverse your biological age, and about how anti-aging helped him cope with mortality as a teen.

Age backward and maybe live forever with my new book, Super Human. Head on over here to get your copy! 

“My grandfather got cancer [when I was 15]…I thought about life and what life meant and what we were all moving toward,” he says. “Then, after a little more reflection and a lot of reading and so on, I was like ‘Oh, wait, there’s something I can do here.’”

Thanks to Peyer’s work, and the work of other anti-aging researchers and experts, it’s now clear that you can do quite a lot to live a strong, healthy life, no matter how old you get.

This article will look at how you can turn back the clock at a cellular level and keep your body young, regardless of the year you were born.

3 ways to reverse your biological age

1. Upgrade your mitochondria

Your mitochondria are the power plants of your cells — they crank out the energy that runs everything your body does, from breathing to moving to thinking.

Typically, your mitochondria slow down as you age, and you produce less and less energy. Slower mitochondria are a hallmark of aging, and come with fatigue, decreased muscle mass and brain function, declining cardiovascular health, and more.

However, just because most people age that way doesn’t mean you have to. There are dozens of ways to power up your mitochondria and make them stronger than ever before. Upgrading your mitochondria does a tremendous amount for reversing your biological age; it can make you feel like you’re in your twenties again.

Building better mitochondria keeps your brain strong, which can ward off memory loss, dementia, and even neurodegenerative disease like Alzheimer’s[ref url=”https://www.nature.com/articles/nature25143″][ref url=”https://www.sciencedirect.com/science/article/pii/S0925443909002427″].

Stronger mitochondria also keep your heart and muscles strong, which can help you stay in phenomenal physical shape as you age[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709858/”].  

In fact, better mitochondrial function links to overall longevity in a dose-dependent manner — the stronger the mitochondria, the longer people live[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4319988/”].

How to turn on your mitochondria 

• Eat a keto diet (or a variation). In animal studies, a keto diet (lots of fat, very few carbs) makes existing mitochondria more efficient, and also grows new ones (called mitochondrial biogenesis)[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/30027365″]. A keto diet also increases mitochondrial density in the liver and skeletal muscles of mice[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6260463/”]. In humans, ketosis increases mitochondrial function and protects mitochondria from stress-related damage[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/29607218″]. You don’t have to eat keto all the time; if a full keto diet doesn’t work for you, try a cyclical keto diet or a targeted keto diet. Both allow more carbs while still giving you the benefits of ketosis.  
• Do HIIT. Exercise in general is amazing for your mitochondria, but high-intensity interval training (HIIT) is the best type of workout you can do for mitochondrial function. HIIT causes dramatic improvements in mitochondrial energy production[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482849/”][ref url=”https://www.ncbi.nlm.nih.gov/pubmed/30072155″]. It also increases the maximum amount of energy your mitochondria can produce, giving you a bigger energy reserve in your day-to-day life[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6139713/”]. HIIT involves short bursts of intense, all-out exercise, followed by brief rest periods. Here’s a great introductory HIIT workout.  

Related: Why Mitochondria Are the Key to Slowing Down the Aging Process

2. Trigger autophagy

Autophagy is like spring cleaning for your cells. It’s Greek for “eating of self,” which is exactly what autophagy does: your cells sift through their various parts, getting rid of anything that’s old or damaged and replacing it with a shiny new version. Even better, a lot of the old stuff gets recycled and packaged into new materials your body can use.

Autophagy keeps your cells young and new, which means they run faster while producing less cellular waste. Your whole system becomes more efficient.

But when autophagy breaks down your cells age, and you, age with them — disturbed autophagy leads to significantly faster markers of aging[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/21884931″].  

How to trigger autophagy

• Work out. Exercise is one of the best ways to turn on autophagy. Research shows that working out increases cellular turnover (how quickly your cells replace themselves) and cleans out damaged cellular parts, which links to decreased aging[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/30430746″]. Any kind of exercise works, but you might as well do HIIT so you also capitalize on the mitochondrial benefits you read about a moment ago.  
• Do intermittent fasting. Caloric restriction is one of the most powerful ways to activate autophagy, especially for your brain[ref url=”https://www.ncbi.nlm.nih.gov/pubmed/27473756″]. Long-term caloric restriction is rough on your body — you’ll get hungry and have a dip in energy levels, and over time may start to lose muscle. A better option is intermittent fasting, where you take short breaks without food and then eat until you’re full afterward. Intermittent fasting triggers “profound autophagy,” to quote one group of researchers[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106288/”]. Fasting also corresponds with longevity and overall healthier aging[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3919445/”]. Check out this complete guide to intermittent fasting to figure out a fasting schedule that works for you and learn about the benefits of fasting.

Autophagy is one of the best tools you can use to age well.

3. Control stress

Stress ages you faster than anything else. If you want proof, compare photos of presidents before and after their time in office. After a term or two of round-the-clock pressure and stress, they look like they’ve aged 20 years.

Chronic stress ages you in two ways. First, it increases free radicals — compounds that damage your cells and cause inflammation. Free radicals increase when you push yourself past your limit, and if you do that chronically, they speed up aging at a cellular level[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579396/”].

Second, chronic stress interferes with your cortisol production. Cortisol is the hormone you release in response to an immediate threat; it shuts down non-essential functions like metabolism and executive brain function, saving that energy so you can escape whatever danger you’re in. Cortisol also breaks down muscle tissue so you have more glucose in your system to use for short-term fuel[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5579396/”].

That’s all great if you’re running from a tiger. But your brain isn’t good at distinguishing between immediate, tangible threats and more abstract ones (fear of getting fired or too many emails in your inbox, for example). When you have constant, lower-level stressors running, your cortisol continually interferes with your metabolism, brain function, muscle mass, and more. Over time, you’ll end up aging faster than you would otherwise[ref url=”https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3428505/”].

Tools to manage stress:

• Meditation
• Heart rate variability (HRV) training
• Deeper sleep
• Stress supplements
• Adaptogens
• Sensory deprivation

If you live your life well, age really can just be a number. Use these tools to turn back your biological clock and stay young, even as you get older. You’ll feel better than ever.

Read next: Hack Your Longevity to Look Younger, Feel Stronger, and Think Clearly