eslie came into my office worn out and exasperated. She was thirty-six years old, but she felt like she was pushing eighty. She was overweight, a trend that started in her late twenties while taking the antibiotic minocycline for her acne. She struggled daily with fatigue, sluggishness, insomnia, and lack of motivation. Her skin was broken out, her hair was thinning, and she had persistent loose stools. On top of all this was her extensive list of medical ailments: irritable bowel, type 2 diabetes, hyperlipidemia, autoimmune thyroiditis, depression, and anxiety.

After seeing several other GI doctors, a chiropractor, a hormone specialist, and an expensive cash-only functional doctor, she was confused and frustrated by the conflicting recommendations. Here she was at thirty-six, on four different medications with ten supplements to boot. “This isn’t the life I envisioned for myself,” she told me on that first visit. “I’m way too young to be feeling this old.”

Much of her frustration stemmed from not knowing what to eat. What should have been simple had become so complicated. She had gone Paleo in her late twenties to combat weight gain and she soon progressed to the Whole 30. She felt better for a short time on those diets, but when the weight gain and fatigue slowly started to creep back in, she desperately searched for a new diet solution and tried eliminating phytates and lectins. She’d been gluten-free for almost ten years and by the time I saw her in my office, she had completely eliminated grains, legumes, dairy, and nightshades. Her diet now consisted mostly of arugula, avocado, grass-fed meat, and bone broth, with very little variation. At times she’d test herself with some beans or whole-wheat bread, but she’d experience gas and bloating, which the diet gurus she was following warned was proof of inflammation.

“It is maddening to follow all the experts’ recommendations religiously and do exactly as I’m told, only to feel worse than ever and see my weight fluctuate like a yo-yo!” she exclaimed. With each progressive elimination, she’d see at most short-term improvement, only to slide back into the same exhaustive pattern. The last straw came when she tried the ketogenic diet to lose weight, but it just made her diarrhea worse and it was now a bigger problem than ever.

At this point in our conversation, she was physically slumped forward, elbows on her knees, staring at the ground, eyes welled up with tears. I pulled my chair closer to hers and leaned in so we were on the same eye level.

“Leslie, it’s going to be all right. We’re going to get you better.” She looked up, a glimmer of hope in her eye. “I totally get your frustration. This is the most confusing time in human history for people who just want to get better. Too many experts saying too many different things. I need you to trust me. If you’re with me, then this is rock bottom right here, right now. Today is a fresh start for you with a new approach that makes you feel better and restores the real version of yourself that has been missing these last few years.”

Over the following months, Leslie and I worked closely together to make some major changes. We took her off most of her supplements and slowly reintroduced diversity back into her diet. Foods that she had been told were off-limits were brought back at the right time, in the right amount. She began to really enjoy her food for the first time in years. The restrictive diet had been challenging, boring, and futile for her. She got rid of her bone broth and tapered down on her animal product consumption while increasing fruits, veggies, and even whole grains. Artificial sweeteners and processed foods stayed on the sideline. Beans came back on the menu! And while the process wasn’t always easy, we worked through it together.

Front and center in her new way of eating was fiber-rich plants—fruit, veggies, whole grains, beans, and legumes. Why fiber? Because as you’re about to learn in this book, fiber is the heart and soul of true gut healing, and true gut healing leads to better health in everything from your cardiovascular system to your brain health to your hormonal health. It’s really that powerful.

When Leslie emerged on the other side and settled into her new approach, she was beaming with energy. She was having fun experimenting with all the new foods that she’d previously eliminated. She now knew exactly which foods she was sensitive to and was able to include them in her diet on a regular basis by simply being careful with portion size. Twelve pounds had melted away. Meanwhile, getting Fiber Fueled reversed Leslie’s diabetes and dramatically dropped her cholesterol. She was able to reduce the dosage of her thyroid medication, and she was back to having normal bowel movements. Best of all, she felt like herself again: alive, optimistic, and excited for the possibilities ahead of her.

Getting Fiber Fueled can help you with whatever you’re struggling with, too, whether it’s weight gain, hormone imbalances, digestive issues, or you just want to feel better in your own skin. I know this because I’ve seen it in Leslie and in hundreds of my own patients. Now it’s your turn.

The Fiber Fueled program

Perhaps you’re one of the many Americans suffering with digestive issues: heartburn, abdominal pain, gas and bloating, diarrhea or constipation. I know there are at least seventy million of you out there because I personally published that statistic in Gastroenterology, the top American journal in my field, just a few years ago. Without question, gut health starts with the foods that you eat. Unfortunately much of the advice being offered by popular “experts” is dead wrong. I’ve grown tired of watching bone broth and grass-fed meat be touted as gut healing. There’s not a single study to support that, not even a crappy one. Instead of offering recommendations based on trends and pseudoscience, my program offers you a scientifically validated approach that will truly heal your gut by restoring order to your gut microbiome.

Do you have a sensitive stomach? Do you have trouble processing certain foods, like beans, broccoli, and gluten-containing grains? Food sensitivity has become a major issue worldwide, with an estimated 20 percent of the world’s population suffering from some form of food intolerance. I see it every single day in my clinic, and I’m going to share with you the strategy I’ve devised for my own patients to help identify exactly which foods they are sensitive to. I’ll also share my easy, step-by-step plan for how to reintroduce those foods to eliminate the sensitivity and get back to enjoying them again.

If you’re one of the millions of Americans who have an autoimmune disease, then this book is for you, too. Seventy percent of the immune system resides in the gut, literally just a single layer of cells separating it from the microbiota. It’s hard to separate the two—they rise and fall together. By optimizing your gut microbes, we can help get your immune system back on track.

Do you or someone you love have heart disease, cancer, a history of stroke, or Alzheimer’s disease? These are just a few of the dangerous and all-too-common conditions that can improve with this plan. The Fiber Fueled approach doesn’t just benefit digestive disorders. In fact, this is literally the only diet plan that’s been scientifically proven to actually reverse heart disease.

Maybe you consider yourself pretty healthy and just want to stay that way. That’s the situation I’m in as well. I haven’t always been in great shape, but right now, by practicing what I preach, I feel fantastic. I’ve lost nearly fifty pounds, I’m back to my college weight, and I feel like I’ve actually reversed the aging process. There’s real science to support that. This is the only dietary approach shown to lengthen telomeres, which is the part of our cells that cause aging as they get shorter. Longer telomeres have been suggested to indicate slow aging and reduced risk of heart disease, cancer, Alzheimer’s, and Parkinson’s.

You’re going to learn in this book that you are one of a kind with a gut microbiome as unique as a fingerprint. So there is no one-size-fits-all when it comes to diet. Something that works for another person may not work for you, and that’s driven by the individual nature of your gut microbiome. But if you’ll treat me like your doctor, mentor, and lifestyle coach, I’ll walk you through a program that will be personalized and tailored to your unique needs and ultimately guide you to the vibrant health that you deserve.

This book is the consummation of everything I’ve learned about gut health during the two decades that I’ve been grinding to become the best doctor I can possibly be. With the Fiber Fueled 4 Weeks (see Chapter 10), I’ll show you how to use a healthy diet, lifestyle, and high-quality supplements to address the root cause of your problems. This isn’t just a treatment plan; it’s a way of life that will help you discover your healthiest self. Your symptoms will dissipate, your doctor will be shocked when your medicine ends up in the trash, and you’ll enjoy the vibrant health you’ve always wanted.

Sadly, I must admit that our health care system has failed you

When I was younger, it drove me nuts when people would say that health care in America sucks. I definitely took it personally. You have to understand, for sixteen years I toiled, sacrificed, and committed every last ounce of energy that I had to that “sucky” health care system. I took out huge loans so that I could go to Vanderbilt for undergrad and Georgetown for medical school. I worked six days a week, at work before sunrise and home after sunset, for what I calculated was less than minimum wage after medical school. My family would be off on vacation together, and I’d be on call in the hospital wearing the same boxer shorts I wore yesterday because I was too tired to do my laundry. (For the record, I don’t do that anymore!)

But now I get it. There’s a reason why the United States is ranked forty-third in the world in life expectancy. We have a health care system that’s great at identifying problems once they exist and then trying to manage them with a combination of pills and procedures. Sure, we can improve symptoms or slow disease progression in some cases, but it always comes at a cost. It’s sick care, not health care. There is little to no focus on prevention.

What we’re missing is an acknowledgment that a couple of milligrams of medicine will never be able to overcome the effect of what we eat. Each of us consumes an average of three pounds of food per day. Keeping the math simple, that’s one thousand pounds of food per year, meaning we’ll each consume about eighty thousand pounds of food during our lifetimes. Somehow, our medical system doesn’t want to acknowledge that these eighty thousand pounds of food matter, but I’m telling you right now: a few milligrams of medicine will never be more important than the eighty thousand pounds of food you eat. When we wait for disease to manifest, we’ve already missed our greatest opportunity. As Benjamin Franklin said, “An ounce of prevention is worth a pound of cure.”

Simply put, the greatest determinant of your health during your lifetime is the food that you choose to eat. As it turns out, your diet is also the greatest determinant of the health of your microbiome. In other words, you could nourish your body with life-giving food and reap the rewards of better health. Or you can punish your body with poisons disguised as food that actually take health away with every bite.

Unfortunately, our health care system simply ignores the role of nutrition in health and disease. Consider medical education in the United States. Medical students spend months learning the nuances of drug pharmacology, but formal nutrition training can be just two weeks or less. For me, that training occurred during my second year of medical school. It would be more than ten years later that I would finally complete all of my training to be a licensed gastroenterologist. And during that entire ten years, it was never mentioned again.

And did you know that even if I provide nutritional counseling, there’s no way for me as a gastroenterologist to bill for the time that I use to do that? Look, I’m not telling you this to say, “Pay me more!” I’m telling you this to say that our system actually penalizes doctors for taking the time to discuss nutrition. I’ll use my office as an example. We currently have three doctors and about fifteen employees. That means that I am personally responsible for covering the salaries of five individuals before I see even a dime. So uncompensated time becomes rather costly. Sadly, this creates a major deterrent to most doctors incorporating nutrition into their practice.

For me, I’ve built a successful career by forgetting the money and the rules and just doing what’s best for my patients. When I finished my training and went into practice for the first time, my patients would ask me fairly intuitive questions. “Dr. B., what should I eat so I don’t get so much gas?” “Hey, Doc, what’s the best food to prevent diarrhea?” “So I was wondering, can diet help me control my ulcerative colitis?” I have a strong, intrinsic motivation to provide the very best care for each person who walks through my office door, and I just couldn’t stand having a patient ask me something like this and not be able to provide an answer.

While I was searching for answers to these questions in my medical texts, a series of events in my personal life were leading me to conclusions about the role diet plays in our health that frankly shocked me. What I discovered was eye opening—and as a result I was motivated to completely change my approach to medicine and break free from the status quo, setting me on a mission to spread this message of truth. I will not stop. It’s too important, and people urgently need to hear this.

My personal path to better health

I’m the guy who always has a five- and a ten-year plan and believes that it’s all going to come to fruition. But never in a million years did I think that I’d one day be an advocate for plant-based gut health. To understand why, you have to understand my background.

I was raised on the standard American diet. Nothing against my parents: I think this is how most kids were raised in the early ’80s. It was normal in our house to eat Doritos and drink Purplesaurus Rex Kool-Aid every single day. Convenience reigned supreme. There were a lot of SpaghettiOs with Meatballs, Chef Boyardee Ravioli, and frozen burritos.

In high school, my parents were divorced and my mom worked full-time. My brothers and I would come home from school, fire up the propane grill, and have a few hot dogs. I became a hot dog connoisseur. Nathan’s Famous and Hebrew National were the top brands, although if you could get your hands on the local Hofmann brand hot dogs, that was next level.

Now, before I go any further, I’d like to take a step back and honor my mom, who was an incredible parent and worked tirelessly to provide for our family. To her credit, she was pretty diligent about reminding us to eat more fruits and vegetables. Being the typical teenage boy, I not only rejected this notion but actually prided myself on pushing the limits of what my body was capable of consuming on the opposite end of the spectrum. I had that sense of invincibility that most of us have at that age. I felt like I could eat anything I wanted and was immune to any consequences.

My poor eating continued. My college diet at Vanderbilt was predominantly cold-cut sandwiches from Jersey Mike’s and Jimmy John’s with a late-night sprinkling of Wendy’s, Sonic, and Waffle House. I started drinking massive quantities of soda to the point where it became a two-liter-per-day habit. During medical school at Georgetown I was obsessed with Wisemiller’s Deli, which was a short walk from campus. These two subs were the ultimate back then:

Honestly, it’s incredible that I never had a heart attack. I had those two sandwiches at least three times a week.

This pattern of unapologetically eating poorly may seem cheeky or cute, but it was taking a toll on my body. As I became busier with work, took less time for exercise, and started to inch closer to age thirty, I began gaining weight, leaned heavily on coffee to get me through the day, and generally felt unwell.

Things came to a head during my year as chief medical resident at Northwestern. All of my dreams were coming true professionally. Beyond being selected as the chief medical resident, which is a huge honor, I had received all the other major awards in our residency program. I was already the author of eight scientific papers in the top gastroenterology journals and my mentors, two of the most famous GI doctors in the country, Drs. John Pandolfino and Peter Kahrilas, were touting me as the next great clinical investigator. Northwestern was paying all of my expenses so that I could get a master’s degree in clinical research, which I was doing in night school in addition to all my other responsibilities.

Everything from the outside seemed like it was going great, like off the charts better than my wildest expectations. But on the inside I was miserable. I was completely exhausted, overworked, and the invincible feeling of my younger years was gone as my body started to change. My weight crept higher and higher until I was nearly fifty pounds overweight. I didn’t like the way I looked or felt, but I was too busy to do anything about it.

It never crossed my mind that having dry-aged steaks at the Chicago chophouses twice a week with the hospital bigwigs or grabbing chili cheese dogs and Italian beef sandwiches on the way home wasn’t doing me any good. I was a celebrated doctor at one of America’s elite medical institutions, and I had such little awareness about nutrition that I was completely incapable of advising my patients, let alone myself. In hindsight, of course, it’s obvious how unhealthy my diet was. It’s not that I thought I was eating healthy. It’s more that this was normal for me. I’d been eating this way for years, so why should I change things now?

The following year I moved to Chapel Hill for my gastroenterology fellowship at the University of North Carolina, the top GI division in the country. I stopped seeing patients for eighteen months and was completely immersed in the world of clinical research as a cancer epidemiologist. During this time I presented more than forty times at national meetings; I published more than twenty papers in the top peer-reviewed journals in my field; I was even selected to give the Presidential Plenary on the biggest stage at the biggest international GI meeting of the year, Digestive Disease Week. With the help of my amazing mentor, Dr. Nick Shaheen, we were shifting paradigms.

While in Chapel Hill, I met my future wife, Valarie, and that’s when things really changed. The way she ate was completely different from the way of anyone I’d ever met. We’d go out to dinner at a nice restaurant, and there’d be a menu filled with a myriad of steaks, chops, poultry, and seafood, but she would get the vegetable plate. Huh? I kept it to myself, but on the inside I had an eyebrow raised. Honestly, I didn’t have any friends who were vegan or vegetarian. This was a mind-boggling experience for me.

But I couldn’t contend with the results. Val ate without restriction. She never worried about portion size and yet never seemed to have issues controlling her weight. She was smoking hot! (And still is.) Meanwhile I was over here sweating out thirty-minute workouts plus a forty-five-minute run every day, and physically strong but still carrying far more weight than I was comfortable with. The way she ate made me curious, so I started to experiment at home without telling her. At first it was making big smoothies with kale and berries that I would do as a replacement for fast food. Immediately, I noticed that I didn’t have that post-meal hangover where you’re just completely exhausted for two or three hours. I loved the way I felt on those days—lighter, more energized, stronger. I also noticed changes with my body—glowing skin, thicker hair, thinner face. My clothes started to fit me differently. My mind had more stamina for work. My mood was lifted and optimistic.

I was feeling so good that I began to wonder why I’d never heard anything about the benefits of a plant-based diet in my medical training. My assumption was that there must not be any studies, that it must be empiricism. The advantage of having a master’s degree in clinical investigation, doing an epidemiology fellowship at the number two school of public health, and publishing more than twenty scientific papers is that you don’t need someone else to interpret the research for you. You do it yourself. So when I went to the medical literature, I was absolutely shocked by what I found. There was a mountain of evidence to support the way I was feeling. We’re not talking a few bad studies where the truth was stretched or there were hyperbolic claims. I’m talking about study after study providing a uniform, consistent result. Plants are good for our health.

There’s so much to love about eating plants. They’re nutrient dense and calorie poor, the ideal weight-loss combination. They have vitamins, minerals, antioxidant compounds called polyphenols, and unique medicinal chemicals only found in plant food called phytonutrients. But there’s one particular part of the plant that absolutely stole my heart—FIBER. Everything I thought I knew about fiber has been turned on its head, and I now legitimately believe that this is the single most important missing piece in the American diet. As you’ll see in this book, this isn’t your grandma’s fiber. This is the true gut health game changer.

As time went on I continued to make changes in my own life. It wasn’t an overnight or radical change. These were small choices over the course of time that were adding up—eliminating soda; cutting out fast food; adding in plant-based smoothies, soups, and salads. Exploring different flavors of ethnic foods that I hadn’t tried before—Indian, Thai, Vietnamese, and Ethiopian. I’m drooling just thinking about them. As I was going through this exploratory phase and making these changes, my body was changing, too. I couldn’t lose weight on hour-long workouts when I ate poorly, but I was now so busy both professionally and personally that I didn’t have time for exercise and the weight was melting off. As I brought myself closer and closer to a fully plant-based diet, I saw progress and improvements in my health and body. I was pescatarian for several years, and when I gave up the fish, eggs, and dairy I lost another fifteen pounds within a few months. I wasn’t restricting myself; I mean I was crushing some serious food—diving face-first into delicious plant-based meals and barely coming up for air. Meanwhile I was down to my college weight. Jeans that for several years I had to jump off the bed to fit into needed a belt. And the belt needed new holes. People were saying to me everywhere I went, “Have you lost weight?” I was getting older in years, but apparently younger in appearance because I increasingly was being questioned if I was really old enough to be a doctor.

When I (finally) went into practice for the first time after sixteen years as a trainee, I was armed with a clinical skill set that had garnered me the top awards in both residency and fellowship, elite research training that empowered me to interpret the studies myself, and the wholehearted belief based upon the studies I’d read and my own personal experience that diet and lifestyle were at the root of all health and disease. Add to that my innate drive to provide my patients with the best care regardless of the money or the rules, and what came from that is a formula that blends the best of Western medicine with a scientifically validated nutrition and lifestyle approach.

The most shocking part for me was how well it worked. I shouldn’t have been so surprised, since I’d experienced the benefits firsthand and seen the powerful science in the studies. I truly believed that if I could have just one patient make these lifestyle changes, then I’d done more good than if I treated an entire month’s worth of patients with medicine. But the crazy part is, hundreds of my patients were making lifestyle modifications. Even by just making small adjustments, they were seeing a difference. But the ones who made me truly excited were those who made radical changes. I was as excited as they were as I watched them transform into the healthy, vibrant people they had always wanted to be.

As I witnessed this happen time and again, I began to feel an increasing sense of urgency to share this message of plant-based gut health. It wasn’t enough to share this story with my patients behind closed doors. Everyone deserved to hear this truth and to be given the opportunity to transform their life for the better. The world needs this healing!

I’d witnessed the confusion that the internet and so-called gut experts had created by promoting messages that were on trend but completely lacking any scientific basis. I’d seen far too many patients harm their bodies with the latest fad diet. These were well-intentioned people who were motivated to improve their health and willing to make lifestyle changes to make it happen. But unfortunately the advice they were being fed by the system was failing them. They were told, “Do this and you’ll be better,” only they weren’t better. They were worse. The philosophy of “eliminate the symptoms by eliminating the food” was not only failing them, it was giving many of them an eating disorder. Some just orthorexia, but I’ve seen numerous cases of full-blown anorexia nervosa start with commitment to a restrictive diet. And as I watched, the entire popular conversation on gut health was building momentum yet missing the most important point—that it’s the plants in your diet that fuel a healthy gut.

So I decided to create an Instagram account, which I titled @theguthealthmd, to share my message on a broader scale. Completely new to social media, I had no idea what to expect. Through word of mouth, a few podcast appearances, and a profile piece by our local newspaper, I began to get a steady stream of new followers to my account. Messages began pouring in from people all over the world, telling me about the improvements they were seeing in their lives through making the adjustments I recommended. I heard stories of people who were losing weight, able to come off medications, and feeling better than they had in years.

I soon realized that it wasn’t enough. In order to give people the opportunity to really make lasting change and transform their lives, I needed to share the entire step-by-step plant-based gut health program that I was using with my patients in my clinic. That became the book you are holding in your hands right now.

I want to welcome you to the start of an exciting, transformative journey. I’ve seen the results from this program time and time again in my own patients, and now you can experience those results for yourself. As you follow this program, you will optimize your microbiome, eliminate cravings, strengthen your immune system, improve energy levels, and resolve digestive issues. This is not a fad or a diet; this is a lifestyle that empowers you to better health. With a “health mindset,” you will effortlessly level up with healthy habits and your gut microbes will rejoice as they thrive on being Fiber Fueled.