Younger You

Reduce Your Bio Age and Live Longer, Better


By Kara N. Fitzgerald, ND

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Based on the groundbreaking study that shaved three years off a subjects' age in just eight weeks, discover a proven, accessible plan to prevent diseases and reduce your biological age.

It’s true: getting older is inevitable and your chronological age can only move in one direction. But you also have a biological age, which scientists can measure by assessing how your genes are expressed through epigenetics. Exciting new research shows that your bio age can actually move in reverse—and Dr. Kara Fitzgerald’s groundbreaking, rigorous clinical trial proved it’s possible. By eating delicious foods and establishing common-sense lifestyle practices that positively influence genetic expression, study participants reduced their bio age by just over three years in only eight weeks!  

Now Dr. Fitzgerald shares the diet and lifestyle plan that shows you how to influence your epigenetics for a younger you. In Younger You you’ll learn:  

  • It’s not your genetics that determines your age and level of health, it’s your epigenetics 
  • How DNA methylation powerfully influences your epigenetic expression 
  • The foods and lifestyle choices that most affect DNA methylation 
  • Simple swaps to your daily routines that will add years to your life 
  • The full eating and lifestyle program, with recipes and meal plans, to reduce your bio age and increase vitality  
  • How to take care of your epigenetic expression at every life stage, from infancy through midlife and your later decades  

We don’t have to accept a descent into disease and unwellness as we age as inevitable: when you reduce bio age you reduce your odds of developing all the major diseases, including diabetes, cancer, and dementia. With assessment tools for determining your bio age, recipes, and plans for putting it all into practice,Younger You helps you repair years of damage, ward off chronic disease, and optimize your health—for years to come.  



What if I told you, you could be younger tomorrow than you are today?

Some part of you would probably be very excited. You did, after all, pick up a book called Younger You. But there’s probably another part of you that would be thinking something along the lines of, “Yeah, right.”

But what if I followed that up by saying, it’s true? And that you can do it simply by changing your diet and making some very doable modifications to your lifestyle—in other words, without expensive or high-risk drugs, or fasting for twenty-two hours a day, or any other so-called biohacking strategies?

“No way,” you’d think.

I have two words for you: Yes way.

In fact, I have a two-month program that reversed the bio age of its participants by over three years.

I am the lead author on the groundbreaking, rigorous clinical pilot trial that asked participants to eat plenty of delicious food and adopt a handful of moderate practices—such as getting seven hours of sleep a night and practicing relaxation for ten minutes twice a day—for eight weeks. We measured their biological age before the study began and again when it ended. And frankly, the results blew our doors off—our study participants lowered their biological age by an average of 3.23 years (compared to the control group, who received no intervention)!

This is where I need to point out that our study, while rigorous, was small. It’s technically a pilot study, meaning it’s designed to provide proof of concept and open the door to larger studies (which we are working on as I type). And yet, combined with our years of clinical experience using the program that we studied and that I outline in this book, it is as clear that we are headed in the right direction as it is that we need to keep researching.

In this book, as I discuss strategies to reverse biological age, you’ll see that much of the research I cite is on animals or in human cells. While there is some research in humans (which I cover), there is significantly less (hence our trial being “first of its kind”). Although this is a young field, multiple lines of evidence converge on the conclusion that we might be able to control how long and how well we live through a combination of diet and lifestyle changes. In this book, I’ll show you how you can follow essentially the same path that our study partipants and clinical patients have followed to become healthier and younger, too.


It’s true that getting older is inevitable: no amount of wizardry can change how many years old you are. Although we all age with time, we don’t all age equally. Aging is a complex process influenced by many factors, and even though two people can have the same chronological age, their life expectancy and living quality can be vastly different. That’s because, in addition to your chronological age, which can only move in one direction, you also have a biological age—or, as I like to call it, your bio age. And your bio age can move in reverse.

Bio age is based on the premise that our bodies are constantly subject to damage and degradation from internal and external sources. By assessing how much damage has accumulated in your particular body, your bio age shows how old your tissues, systems, and even your genetic material are. In other words, you could be fifty chronologically but have the same amount of damage to your body as a typical fifty-eight-year-old. With our Younger You program, you could be fifty but repair your overall level of damage to that of someone in their forties. It’s like turning back time.

While there have been various tools for assessing bio age for a while now, the accuracy of these tools has been mediocre at best. But recently, science has taken a massive leap forward in this arena. We can now measure bio age with exquisite accuracy by assessing how your genes are expressed in a revolutionary field of study known as epigenetics. “Epi” means “above;” epigenetics refers to the biological markers that sit on top of your genetic material and dictate which genes are turned on and which are turned off. To use a computing analogy, your DNA is the hardware—it is what it is. It can be damaged, and it can be repaired, but without software, it can’t do much. So, what’s the software? That is epigenetics.

So far, just a handful of human studies have shown that bio age can move in reverse. This is an extraordinary achievement, but these studies have relied on medications, and/or have taken a long time, and/or were measuring a population that started less than healthy (less healthy individuals tend to be older biologically and can therefore get younger simply by returning to health). Our study is the first to show that significant age reversal might be brought about in healthy individuals through doable diet and lifestyle changes alone, and possibly accomplished in a matter of weeks. No magic potions required. Just tweaking your normal lifestyle: food, sleep, exercise, and relaxation, but nothing beyond what most folks consider to be basic self-care.


Beyond our study participants, every one of the hundreds and hundreds of patients who have come through the doors of my clinic in the past several years have either been given, as their primary intervention, the eight-week eating plan and lifestyle prescription that our study participants followed, known as the Younger You Intensive, or been coached to incorporate some of these foods and practices—a less intensive, longer-term version known as Younger You Everyday.

At my clinic, we see patients with chronic conditions who have tried other medical avenues with limited success. They are often complex cases that represent a broad swath of the illnesses that are so common today—autoimmune diseases, chronic allergies, autism, digestive issues, diabetes, cardiovascular disease, infertility, cancer, Lyme disease, and neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and dementia. These are folks who have struggled with a conventional medicine model because their medical realities don’t necessarily fit clinical definitions, and if there are prescribed treatments, their side effects chip away at quality of life.

Regardless of their official diagnosis, the majority of our patients are at some phase of midlife, and they also want to look and feel younger. (We also have a great pediatrician on our team who uses the Younger You principles with children and young adults—because as you’ll learn, they are important in all life stages.) That desire is often what gets them to book their first appointment. Yet the results my patients have experienced in search of reducing their bio age are extraordinary. We have seen their chronic, difficult-to-manage symptoms lessen, stabilize, or even go away completely.

For example, I recently started working with a woman who was dealing with a full-blown case of seasonal allergies. Ava had completely lost her sense of smell, her body was covered in hives, and every year she developed a sinus infection so severe that it required antibiotics and steroids. In our first meeting, she was much more interested in developing a plan that would help reverse the signs of aging—the thickening middle, the brain fog, the loss of muscle tone—than she was in addressing her allergies. But by following the diet and lifestyle principles that I outline in this book, she lost weight, regained her ability to think clearly, built muscle, and her seasonal allergies fully resolved.

Ava’s certainly not the only one. Across the board, our patients have reported more energy, better mood and less depression, fewer headaches, clearer skin, lost weight, and less susceptibility to succumbing to viruses. Their digestion improves—with less gas, bloating, diarrhea, and constipation. From a clinician’s perspective, I have seen a drop in their blood sugar and insulin, reduced inflammatory markers, much lower levels of fat in the blood, higher “good” cholesterol and lower “bad” cholesterol, and even lower levels of the antibodies that are hallmarks of autoimmune conditions. Taken altogether, these results demonstrate the far reach of the Younger You program: from the epigenome to whole body balance! Essentially, it appears that we are empowering people to debug their own software.

You can use either version of the Younger You program at any age. Whether you are picking up this book because you want to feel younger or you want to address a specific condition, it doesn’t matter—the Younger You program will help address both. It’s a twofer, as turning back the clock should help clean up the symptoms that go along with aging.

It’s so exciting to me that as we get further into what’s known as the “omics revolution”—the line of study that looks at individual components of physiology such as the genome (your actual DNA), the epigenome (the material that sits on top of your genetic code and dictates which genes are turned on and which are switched off), the microbiome (the microbial population in your gut), and more, and how they interact with each other—we see that humble interventions such as nutrition, sleep, and exercise might be the most impactful and essential tools we have to improve individual health. It’s a massive paradox that it took science reaching this level of sophistication to realize the power of these fundamental interventions, but it’s so validating to me, a holistic physician/lab geek, to see just how exquisitely programmed for wellness we are, if we only understand how to nourish and take care of ourselves.


Our understanding of how to reduce our bio age is occurring just in the nick of time. Life expectancy in the United States has declined for three consecutive years (2015, 2016, and 2017), the longest decline since the period from 1915 to 1918, when World War 1 and the Spanish flu epidemic killed millions—and these numbers don’t even take into account the COVID-19 pandemic that roared across the country starting in 2020.1 It’s not just that we’re living a shorter time; it’s also that we’re spending a longer portion of the time we’re alive with a serious disease that is a leading cause of death—according to information from the World Health Organization, we spend 20 percent of our lives sick.2 (Although we have a life expectancy of 79.3 years, the average age for developing a serious illness is 63.1 years old, meaning we spend the last 16.2 years of our life ill.)3

In his incredible book Being Mortal, Atul Gawande included two graphs: one that showed the trajectory of a life before modern medicine, with limited years of health and then a fairly sharp decline that ended in death…

… and the common path of life we have now that we have learned how to survive, but not necessarily abate, disease. It shows a long, slow, gradual, and honestly, painful decline in quality of life.

Our study and clinical work suggests a third option: that by aiming to support our epigenetics via diet and lifestyle, we might have the possibility of a new trajectory, one that combines the more consistent quality of life of Figure 1 and the overall length of life of Figure 2. Let’s put an end to the sixteen-plus years of ill health we’re all currently destined to endure and turn them back into years of thriving and wellness!

This third option isn’t a new idea—it was first put forth by James Fries, a professor of medicine at Stanford University School of Medicine who published a paper on his “compression of morbidity” thesis in the New England Journal of Medicine in 1980. In it, Fries wrote, “Chronic illness may presumably be postponed by changes in lifestyle, and it has been shown that the physiologic and psychologic markers of aging may be modified.… These considerations suggest a radically different view of the life span and of society, in which life is physically, emotionally and intellectually vigorous until shortly before its close.”4

Our Younger You program aims to postpone chronic illness—and the associated prescription drugs, surgical procedures, and poor quality of life—and improve the physiological markers of aging that Fries referenced using nutrient-rich food and time-tested lifestyle practices to empower the innate and timeless healing systems encoded within your body to slow down and even prevent chronic illness and the “aging” trajectory. By following it, you’ll be aiming to influence your epigenome and genetic expression. No matter your family history, current health status, age, or weight, you can get on a path to raising your level of health, reducing your bio age, and extending your health span—maybe even your life span.


Doing interventions with the aim of working out the kinks in your internal health programming isn’t a new idea. The biohacking trend, where health nuts are trying all manner of aggressive health interventions in an effort to live longer and healthier, is surging. Somewhere in Silicon Valley right now (so many biohackers seem to be male, tech-friendly, and wealthy), someone is injecting themself with human growth hormone, receiving an IV of a young person’s blood plasma, taking an immunosuppressive drug, or even downing a cocktail of gene-editing enzymes and proteins in an effort to achieve maximum performance and longevity. While many of these methods have produced favorable health effects, and believe me, I am paying attention to (and excited about) the latest anti-aging science, for most of us, they’re not available, affordable, doable, or even desirable. Some of them come with their own unpleasant—or potentially even dangerous—side effects. And because we don’t know the long-term consequences of these extreme strategies, we honestly can’t be sure of their safety. And only one of them (getting injections of human growth hormone for a year—something I discuss more in Chapter 1) has thus far been shown to reduce bio age in humans.

Although I love poring through research, I’m also a single mom, a business owner, and a clinician. Time is not something I have extra bits of lying around. As a fifty-three-year-old mom to a three-year-old, I am heavily invested in living as long as I can and aging as healthfully as I can.

I, like you, need any program to be doable. And while you can’t expect to have a positive, lasting effect on your bio age without actually following the program, you could also accelerate bio aging (as you’ll soon learn) if the whole program stresses you out with time and energy demands! You also won’t be able to achieve your goals if the eating and lifestyle strategies take too much time and energy to figure out and activate stress responses that could adversely affect your epigenetic programs. My goal is to provide strategies that are as palatable and accessible as they are effective, based on our current clinical results. As we expand the number of people that are engaged in these interventions, as our empirical body of knowledge increases, and as we capture more and more of the “personal” variations in responses, we will be able to further optimize and personalize our plan.

There’s an adage that it takes fifty years for medicine to translate new scientific discoveries into action. This number has come down some since the advent of the internet, but not by much. By writing this book, I’m seeking to dramatically reduce that timeframe.


In the pages to come you’ll learn how to support your body’s ability to slow biological aging and increase your health span with the following:

Lists of delicious foods that deliver the nutrients your body can then use to balance your epigenomic software

A list of specific foods to avoid because they appear to negatively impact the epigenome and, thus, make you age more quickly

Recipes and meal plans that have been tailored to deliver the nutrients that support healthy genetic expression

Lifestyle practices, such as getting-to-sleep techniques and specific exercise and meditation dosages that support your body’s ability to regulate its genetic expression for optimal health

Strategies to minimize the things that can profoundly damage the epigenome and significantly throw off genetic expression, such as exposure to toxins, stress, and an overgrowth of unfriendly gut microbes

So that you understand the power of these diet and lifestyle strategies, in Part 1 you’ll learn more about how your epigenome directs your genes to keep you alive and healthy—or contributes to aging and its frequent companion, illness. I’ll introduce you to DNA methylation, which is a mechanism of epigenetic expression, as well as the formula to the Younger You plan.

Whether you’re facing a health challenge or are very motivated to reverse the hands of time (or both!), you’ll find guidance in Part 2, in which I’ll share the eight-week Younger You Intensive program—the exact version that our study participants followed—as well as the more flexible Younger You Everyday, which you can adopt as your long-term eating plan after finishing the Intensive. Or if you want a more gradual transition into the Intensive rather than a full jumping in, you can start with the Younger You Everyday and then move over to the Intensive.

And in Part 3, I’ll share insights on how to think about your genetic testing results if you have them, and my thoughts on how to tend to the all-important tumor-suppressor genes (the most famous one being BRCA) so that they remain hard at work for you throughout your life, keeping cancer (and aging) at bay. (As you’ll see, the expression of many genes, including tumor-suppressor genes, has been shown to be favorably influenced by specific nutrients; I’ve started thinking of these genes as nutrient-responsive genes.) And you’ll learn how to optimize your lifestyle at every stage of life in a way that supports your epigenome, and perhaps even pass those effects on to your children, whether you already have them, are planning for them, or even if you have adopted or fostered children. Finally, we’ll take a look at what other anti-aging strategies are currently in development—their possibilities and their risks—as well as other ways DNA methylation is changing health care as we know it.


Both versions of the plan are designed very specifically to nourish your epigenome, and both rely heavily on whole foods—some that you may already be used to, such as eggs and dark leafy greens, as well as a few that are a little more “out there” but that I think you’ll be convinced to try once you learn just how potently anti-aging they are (and you try our delicious, easy recipes for them), such as beets, shiitake mushrooms, and liver.

While the Younger You eating plan may be a different way of eating for you, it is undeniably delicious, very filling, and uberflexible: we have customized it for patients who either are constantly on the road (and don’t want to pack food) or who live in food deserts and don’t have access to high-quality food, and they have radically improved their health and become younger, too. Both the Younger You Intensive and Everyday programs can work with whatever therapeutic diet you are currently eating, whether that’s an elimination, gluten- or grain-free, plant-based, low-glycemic, or keto diet. In fact, this is how we use the program in my clinical practice: everyone is prescribed the plan, but then we personalize it by layering it into their specific therapeutic dietary prescription.

The Everyday version is designed to help you keep the gains you’ll reap with the Intensive and promote long-term health. It outlines the simple changes you can use to support your epigenome and add years to your life, like trading that extra cup of coffee or black tea for green tea (or yummy Golden Turmeric Milk), swapping your roasted potatoes for roasted beets, sprinkling rosemary on everything, and snacking on blueberries (or our delicious Matcha Coconut Crunch).


I understand that I’m writing this book in an era where there are so many diets. The last thing I want to be is just another fad—particularly when the evidence is so clear that following the Younger You principles benefits all aspects of health. I also recognize that epigenetics is complicated, and that can work against even the most exciting idea being able to cut through the noise. So before I dive into the specifics of what to eat, drink, and do, I’m going to give you a layperson’s tour of aging and epigenetics. Understanding why the Younger You Intensive is as effective as it is will help you see that it’s not just some new diet—it’s a science-backed guide to shaving years off your bio age by promoting a healthy epigenome.

With the Younger You program, if you’re a health nut or committed biohacker in search of longevity, you won’t risk taking your efforts too far, or waste effort—and time—on a less effective dietary program (even the highly respected Mediterranean diet wasn’t nearly as effective as the Younger You Intensive in lowering bio age, as I’ll discuss later); if you’re facing health challenges and seeking relief, you’ll learn how to support your ability to heal at the deepest level; if you’re looking to start a family (whether through biology or adoption), you’ll be able to give your offspring the best support in creating a foundation from which to thrive throughout their lives; and if you’re simply seeking to look and feel your best, you’ll discover a very real opportunity to delay your aging and minimize your risk of disease—in other words, to truly be a younger you.



You know how Facebook shows you memories of old photos on your timeline? And you see a photo from eight, five, or even two years ago and think, “Damn, I looked good! Where have those days gone?”

It’s enough to make you start Googling face creams. After all, when most of us think about anti-aging strategies, that’s what we think about: various lotions and potions to rub on our skin that, in the classic language of advertisements, “minimize the appearance of fine lines and wrinkles.” Or, maybe if we take it one step further, we think of taking hormones that help us feel more youthful. Because, if you’re being honest, seeing that photo in your Facebook memory probably also reminds you that it’s not just the way you look that’s changed; you have a moment of recognizing that your memory seems to have gotten worse, your energy has flagged, and your body has lost some of its ability to do things, whether that’s recover from illness, get up and down from the floor, or open a pickle jar. What you probably aren’t considering is that with every passing year, the door to disease opens wider, as age is the single biggest risk factor for every chronic disease. And no fancy cream, no matter how expensive, is going to help you actually turn back the clock on those things.

The drive for youth is so strong in our culture (the global anti-aging industry was expected to approach $220 billion in 20211), but most of us don’t connect the dots between our diet and lifestyle choices, an accelerated rate of aging, and an increase in risk for chronic disease. In fact, your bio age is the single biggest risk factor for all the major diseases, including diabetes, cancer, and dementia.


The good news about our current aging reality is that modern medicine has resulted in longer and longer life spans. We’ve reduced incidences of many infections—COVID-19 notwithstanding—and disabling diseases so that the average person doesn’t die of flu or tuberculosis, and lives to a higher age. The bad news about longer life spans is that we have simultaneously increased the incidence of chronic, noncommunicable diseases, such as dementia, heart disease, and cancer. (As we get sicker with these chronic diseases, ironically, our risk of communicable diseases increases exponentially—as evidenced by the United States experiencing so many deaths from COVID-19.)

A whopping 80 percent of adults over sixty-five have one chronic disease. And a full 77 percent have at least two! But it’s not like we turn sixty-five and—boom!—we get the disease like some kind of ghoulish birthday present. We’ve been on this path our whole lives—one in three Americans under sixty-five have metabolic syndrome, a collection of symptoms that includes high blood pressure, high blood sugar, high cholesterol or high triglycerides, and an apple-shaped body (accompanied by belly fat) that paves the way to full-blown chronic disease.

The scientific and medical communities have responded to this rise in disease incidence by focusing on researching and treating the diseases themselves. The problem is that once you take steps to prevent, say, heart disease, you take your eye off cancer prevention. It’s what Dana Goldman, director of the Schaeffer Center for Health Policy and Economics at the University of Southern California, told PBS Newshour, “It’s almost like Whack-a-Mole, where you push down on one disease and another one pops up.”2


  • "It is a new era—aging 'backward' is no longer a fantasy, it is now a fact proven by clinical trial. Dr. Kara Fitzgerald, lead author of this paradigm-shifting trial, now describes her approach in her new book, Younger You.  This is the first book in the new era of 'aging reversal' medicine and health, and for all of us who are aging, this is a must-read."—Dale Bredesen, MD, professor and author of the New York Times bestseller, The End of Alzheimer’s
  • "Younger You challenges the long held notion that we are helpless as it relates to the seemingly inexorable decline in our physical health as time marches on. Dr. Fitzgerald makes it clear that we can absolutely change our destiny as it relates to various parameters associated with aging and provides a straightforward program for achieving this important goal."—David Perlmutter, MD, author, #1 New York Times bestseller, Grain Brain, and Brain Wash
  • "After years of working alongside Dr. Fitzgerald on reaching and maintaining optimal health, I can safely say she is one to look out for to not only live a longer life, but a healthier and more vibrant one."—Amy Myers, MD, New York Times bestselling author of The Autoimmune Solution and Thyroid Connection
  • "A lifestyle program has never been more worthwhile or more revolutionary than Dr. Fitzgerald’s in Younger You. She shows how the simple things like nutrition, exercise, and daily routines can profoundly affect your quality of life—and that it’s never too early or too late for the whole family to start thinking about optimizing their epigenetic expression.”—Sara Gottfried, MD, three-time New York Times bestselling author of The Hormone Cure
  • "Finally a well-explained, dynamic, science-backed guide to optimizing your health by affecting the core of what makes all of us tick—our genes. I’ve been using Dr. Fitzgerald’s program in my practice for years and I’m so pleased this information is now accessible to all."—Mark Hyman, MD, fourteen-time New York Times bestselling author and founder and director of The UltraWellness Center
  • “I first learned the power of nutrition, exercise, and lifestyle to dramatically improve our lives when treating my multiple sclerosis. Now Kara Fitzgerald has taken it a step further with her clinically-proven program for a longer and more vibrant life.”—Terry Wahls, MD, author of The Wahls Protocol: A Radical New Way to Treat All Chronic Autoimmune Conditions Using Paleo Principles
  • "As a scientist and educator in nutritional epigenetics and longevity, I commend Kara's extraordinary ability to make science accessible and actionable to a lay audience. Her guest lecture for my course on the biology of longevity at Stanford University drew rave reviews from my students. I will recommend Kara's new book Younger You to my students who want to deepen their knowledge and practice of nutritional longevity.—Dr. Lucia Aronica, PhD
  •  "Dr. Fitzgerald is among the first to realize that epigenetics is destined to be a game-changer for 21st Century medicine. Now she shares her program to modify our epigenetics safely, with exercise, a natural diet and a surprising array of other practices. Let's try it!"—Josh Mittteldorf, PhD, author of Cracking the Age Code
  • "Younger You leads us through a compelling narrative linking food, genes, epigenetic programming of genes by life experiences and how this guides us to take control of our own lives. The book provides an engaging, clear and understandable presentation of the complex science of epigenetics and the developmental origins of health and disease for the general audience."—Moshe Szyf, PhD, McGill University Medical School
  • "Dr. Fitzgerald has published groundbreaking research that proves that we can change the aging of our body through a specific lifestyle intervention program. Now she has made this program available for all of us to benefit from in this extraordinary book. This is a 'must' for anyone interested in what they can do in slowing the aging process naturally."—Jeffrey Bland, PhD, president, Personalized Lifestyle Medicine Institute

On Sale
Jan 17, 2023
Page Count
512 pages
Hachette Go

Kara N. Fitzgerald, ND

About the Author

Kara Fitzgerald, ND, IFMCP, is the first-ever recipient of the Emerging Leadership Award from the Personalized Lifestyle Medicine Institute in recognition of her work on DNA methylation. Receiving her doctorate in naturopathic medicine from the National University of Natural Medicine, she lectures globally on functional medicine, is on the faculty at the Institute for Functional Medicine (IFM), and is an IFM Certified Practitioner with a clinical practice in Newtown, Connecticut. She runs a Functional Medicine Clinic Immersion program for professionals and hosts the podcast New Frontiers in Functional Medicine. She lives with her daughter in Connecticut.

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