Can Keto Actually Work For Hard-Training Endurance or Power/Strength Athletes?

inline_sami_rowingKeto is red hot these days, and it’s not going away anytime soon. Call it the latest dietary fad, but keep in mind a great insight Robb Wolf told Joe Rogan on his podcastketo was “likely the default human metabolic state” over the past 2.5 million years of human evolution. Only with the extremely recent (on the evolutionary timeline) advent of civilization have we been stuffing our faces with carbs and snuffing out our magnificent ability to generate ketones as a clean-burning alternative fuel source to dietary carbohydrates. And we certainly were compelled to evolve a highly efficient mechanism to keep our high energy demand brains fueled with glucose or the glucose-like substitute of ketones at all times—for this was a matter of life or death in primal times. When our ancestors were starving, they needed to keep working hard, and concentrating hard, to find food!

The thought leaders and scientists in the keto scene have been establishing the case for keto very well: ketogenic eating really works for virtually everyone if you follow the correct approach. You can expect not only the efficient reduction of excess body fat, but a profound anti-inflammatory effect that can correct assorted autoimmune and inflammatory conditions; improved cognitive function and protection against the disturbingly prevalent conditions of cognitive decline (that are being increasingly connected to high carb, nutrient deficient diets); and assorted anti-aging benefits such as enhanced autophagy (the natural cellular detoxification process) and apoptosis (the programmed death of dysfunctional/pre-cancerous cells).

Keto has also been touted as potentially improving athletic performance for both endurance and strength/power efforts. However, this has become a matter of some dispute in the fitness world, as high calorie burning folks have a hard time embracing the idea that they can benefit from consuming fewer calories and rejecting the obsession with immediate refueling to restore glycogen after vigorous workouts. Today’s post will introduce you to the amazing Sami Inkinen, one of the world’s most accomplished endurance athletes who also has a high profile career as a Silicon Valley entrepreneur. Sami has taken keto experimentation to the extreme, and quantified everything beautifully to illustrate the amazing transformation that happens when you become a fat- and keto-adapted as an athlete.

The Keto Reset Diet goes into great detail about how keto can benefit endurance performance by making athletes virtually bonk-proof—able to perform for hours on end with a dramatically reduced need for carbohydrates as a fuel source. Sami’s story is told in further detail in Primal Endurance and on his blog. Here, he has taken the time from his busy schedule to share some extensive thoughts on how you really can succeed in endurance sports while eating ketogenically, if you follow the correct approach.

Being fat- and keto-adapted is an obvious benefit for endurance, since endurance performance is predicated on being burning more fat and sparing glycogen. The benefits of keto for strength/power athletes is less logical, because high intensity, high glycolytic (high glucose burning) workouts would seem to beget carbohydrate consumption in order to recover and replenish glycogen-depleted muscles. However, keto pioneers in the power scene have discovered amazing results, which are being increasingly validated by science at places like the Applied Science and Performance Institute in Tampa, FL, with Ryan Lowery and Dr. Jacob Wilson. Luis Villasenor, the legendary “DarthLuiggi” in the keto scene, has followed a ketogenic diet as a competitive powerlifter and bodybuilder for some 16 years! Through his program, he and his team have coached thousands of high intensity athletes to improved performance and improved body composition. Luis is a living, breathing example that you do not have to destroy your health with massive overconsumption of carbs and protein to maintain a bodybuilder physique.

We’ll hear more from Luis and others about how to utilize keto for high intensity performance in the future. Briefly, fasting and ketogenic eating have been shown to have a remarkable protein-sparing effect. It makes evolutionary sense that your body would initiate assorted mechanisms to preserve lean muscle mass when you are starving. Unfortunately, in the carbohydrate dependency paradigm, your body routinely converts lean muscle tissue into glucose via gluconeogenesis to meet your energy needs, especially for the brain (only two percent of body weight, but consuming 20-25 percent of total calories!)— a ravenous consumer of glucose. For carb dependent athletes who don’t remain constantly glycogen stocked, bad things happen with fatigue, delayed recovery, and loss of lean mass. This is why bodybuilders have been urged to eat their six small meals throughout the day and obsessively overconsume protein and carbs to spur growth. Luis and others have shattered this paradigm by getting big, strong, and lean in full keto mode.

Back to endurance, where for decades the conventional thinking was to carb load with your evening pasta feeds and morning cereal troughs, train super hard so you can go harder and longer without falling apart, and possibly train the body to store more glycogen (yes, it’s possible to a minor extent, but soon you will learn how irrelevant this is), and to stuff sugary drinks, gels, and cubes down your throat, hopefully without gagging. Finally, it was believed essential to stuff your face with more carbs immediately after workouts in the so-called “window of opportunity,” when your muscles can restock glycogen optimally.

We are in the age of a transformation in the endurance scene to the extent that I might boldly proclaim that the endurance champions of the future will possibly be full keto or at least cyclic keto to gain a performance and recovery boost. To date, our endurance champions have fueled their efforts with sugar and beige glop—my pet nickname for grains. Who can forget when Olympic swimming legend Michael Phelps’s diet was presented with great fanfare a decade ago as totalling 12,000 calories a day, featuring heaps of refined carbohydrates. Phelps later admitted to exaggeration, and readers at this site can appreciate the irony of his correction that he really only ate 8,000-10,000 calories…featuring heaps of refined carbohydrates. I still get giggles for a quip I wrote over 30 years ago in my first endurance training book relating to the prevailing ethos of the endurance community: “if the furnace is hot enough, anything will burn.” I related my impressive pre-race meal before my fastest marathon performance: a couple beers, a bag of frozen peas, and a half-gallon of rocky road ice cream—pretty much all that was available at my bachelor pad that night!

As our sophistication in training methods and health and nutrition science grows, we can all appreciate the destruction caused by eating garbage while pursuing ambitious fitness goals, especially when training patterns become chronic. The awakening is upon us, but unfortunately it seems like many athletes are stuck in the old paradigm. Sugary drinks, bars, and gels are still flying off the shelves, and the community as a whole is freely dispensing hall passes to each other and themselves to indulge in nutrient-deficient foods on account of their impressive workouts.

Sami and his mind blowing performances and self-experimentation results serve as a true inspiration for endurance enthusiasts to try something new with an informed and disciplined approach, and reap phenomenal benefits. Not just performance benefits (how about Sami moving his theoretical “time to bonk” value from 5.6 hours while carb dependent to 87 hours when fat adapted?!) but also health and freedom from disease risk factors driven by high carb eating and burning patterns. Enjoy the following commentary from Sami, encouraging athletes to consider a ketogenic approach.

Traditional advice for endurance athletes is to “carb-load” and to consume enough carbohydrates before, during, and after a race for fuel through the entire event and for recovery. But what if I told you that you could run or ride your bike for longer without hitting the dreaded wall? What if I told you that you could even recover faster and improve your metabolic health? All of this is possible, but only if you throw out the advice we’ve all been given about carbohydrates and exercise.

There’s a different path when it comes to fueling our bodies—a ketogenic diet. Restricting carbohydrates and relying on most of your calories as fat induces a state of nutritional ketosis, meaning that your body will use fat—both dietary and body fat—as its primary source of fuel. Even the most lean athlete has tens of thousands of fat calories on hand, so it makes sense to use them! The key is knowing how.

Here are 3 of what I believe to be the most compelling reasons for an endurance athlete to make the switch from a high-carb to a high-fat nutrition plan:

1. You can become virtually bonk-proof

As athletes, we want to be our best and be able to compete at our best. We prepare for months or even years with training plans for both our performance and our nutrition in hopes that we leave our best out on the course. Despite our strongest efforts, many of us know it’s possible to get to a point during exercise when we ‘hit the wall,’ regardless of how well-trained and prepared we are going into an event.

‘Bonking’ or ‘hitting the wall’ typically occurs after about 2 ½ hours into continuous, hard exercise, which corresponds to when glycogen (glucose stores) is really low. When exactly this happens depends on how long and how hard you’re pushing, but when your body can no longer meet the energy demands, it is essentially an energy crisis for the brain. You’re fatigued, not able to think clearly, and if you’ve ever experienced this during an event, you know that it’s simply miserable.

Ever since I experienced my first bonk on my bike, I’ve tried to figure out how to make myself bonk-proof, and eventually realized that I couldn’t do this by simply adding more and more carbs to my nutrition plan. When we eat and train with carbs, our bodies rely on them, but we have a limited ability to store them with a capacity of only 500-600 grams of glycogen (glucose stores), or about 2,000 calories. I’d have to eat gels and bars every 30 minutes to extend the point at which I’d run out of energy, but the ability to eat and absorb that energy while exercising is limited. Alternatively, we have the ability to store nearly unlimited amounts of fat. Even a very lean and small (~120lbs) athlete with low 7% body fat still carries about 30,000 calories of fat. Imagine being able to use that during a race!

So I learned how to rely on fat instead and my brain can rely on ketones (that are produced from fat by the liver) for a nearly unlimited supply of fuel. I’ve essentially made myself bonk-proof, and with fat as my primary source of fuel, I don’t need to eat anything at two hours anymore. It’s literally a game-changer! But becoming a fat-adapted athlete takes time. It doesn’t happen overnight. Just like training for an Ironman doesn’t happen in a week or two, neither does training your body to more efficiently burn fat. Once you become adapted to nutritional ketosis, or keto-adapted, there are several benefits. You rely less on the limited amount of carbs your body has and can more easily and quickly rely on your body’s fat for fuel. You increase the rate at which you utilize fat and you no longer ‘hit the wall’ at 2 ½ hours into an endurance event, even if you don’t have food available. In fact, the recent FASTER study demonstrated that fat-adapted athletes oxidize (i.e. burn) fat at a rate more than twice that of high carb athletes, which means the body has a better ability to access its fat and oxidize it for fuel.

2. You can recover faster

Being a successful high-performing endurance athlete isn’t just about the moments when you are working out or competing. It is also about how quickly you recover so that you can resume your usual workout regimen. Most athletes are familiar with the inflammation, soreness and swelling that comes after any hard workout or race. While some inflammation is necessary to increase muscle strength and is part of recovery from exercise, too much inflammation can interfere with the body’s repair process. It’s a balancing act. Many athletes will try just about anything to reduce post-workout inflammation, from ice baths to taking anti-inflammatory medications to chugging beet juice.

The less pain and soreness you have post-workout, the sooner you can go hard in your workouts again, and the better you might perform in the next race. After fully adapting to nutritional ketosis, I felt (subjectively speaking) a lot less sore and got rid of frequent nagging things like inflamed achilles tendons following the same workouts—racing my wife up Mt. Tamalpais [A 2,500-foot peak in Marin County, CA—just North of San Francisco], while just as strenuous as the times I had done it as a high-carb athlete, didn’t leave me with the same muscle soreness in the days after. It turns out that ketones don’t just function as important energetic molecules, but they have positive effects on cellular processes as well. Studies show that a well-formulated ketogenic diet reduces inflammation levels. Furthermore, I can get right back on the bike the very next day, meaning that I can train more frequently and don’t need as many recovery days.

3.  Your health may not be what it appears

The appearance of physical health and “fitness” can hide serious medical issues. Even if you are fit, strong, and lean, you may not be metabolically healthy.

I had no idea that this was true for me until around 2011-2012. I became a triathlon world champion in my age group and found out that I was prediabetic and metabolically unhealthy—my glucose values were consistently way above healthy ranges. Despite my years of high-level endurance sports, strict performance diets that perfectly aligned with the dietary guidelines, and very low body fat, I was on my way to developing type 2 diabetes. I was shocked to find out that following the low fat and ‘quality’ high carb dietary recommendations had led me to the brink of diabetes, but I was also determined to dig myself out of this hole. Type 2 diabetes and prediabetes are typically treated with medications (and, for some people, eventually surgery), but I wanted to try fixing my metabolic health myself. If following the dietary guidelines had led me to prediabetes, I thought there might be a way to reverse prediabetes—perhaps even by following the opposite approach.

My deep dive into published research led me to realize that the high carb diet recommended for athletes instigated my prediabetes by constantly spiking my blood sugar, and that my intense, regular, high-volume exercise had not been enough to keep my blood sugars in control. It turns out you can’t exercise enough to outrun bad nutrition advice. After finding peer-reviewed clinical research demonstrating that a high-fat, moderate protein, and low-carb ketogenic diet could help me reverse my prediabetes, I completely changed my nutrition plan and started tracking my blood sugar and ketone levels. I was amazed at how useful the regular biomarker information was to tweaking my diet around my body’s individual response.  Everyone truly responds differently to the same foods based on genetic differences, and you never know for certain until you test regularly. By switching to a well-formulated ketogenic diet and a data-driven approach, I successfully reversed my prediabetes and improved my metabolic health across the board.

The bottom line is that sustained nutritional ketosis has allowed me to:

  1. Increase my endurance capacity by providing me access to a larger fuel tank
  2. Reduce post-workout inflammation and thus recovery time, increasing valuable training time
  3. Reverse my prediabetes and improve my metabolic health

You can learn more about nutritional ketosis here in an FAQ by Dr. Stephen Phinney.

In Sami’s journey to becoming bonk proof, he painstakingly tracked his progress in repeated laboratory tests where he measured fuel substrate utilization while riding a stationary bike at a comfortable pace. The results as explained in this graph series (below) are astounding. Ditto for the details of the highly regarded FASTER Study, which compared the fat oxidation rates among elite ultramarathon runners who were on a low-carb, fat adapted diet to elite counterparts consuming a traditional high carbohydrate diet. Dr. Peter Attia, one of the most brilliant minds in the keto scene who now focuses on longevity medicine at his private practice in San Diego and New York City, has also chronicled his amazing transition from sugar burner to fat adapted cyclist. Attia went from burning 95 percent carbohydrate calories at anaerobic threshold to burning 25 percent carbs and 75 percent fat at the same threshold heart rate after a devoted period of dietary transformation. What’s more, Attia achieved an increase in wattage output at anaerobic threshold when fat adapted—in other words, he went faster on fat! This data shatters the notion that keto is only for long, slow endurance performance.

Take a look at Sami’s graphs from repeated performance tests in the Stanford laboratory, as he progressed from pre-diabetic sugar burning machine to a fat burning beast:


Graph 1 (above): Results of Sami Inkinen’s initial performance test from 2009. At 300 watts, he is burning almost all carbohydrates—destined to bonk after a couple hours, maybe three if he can slam down some gels en route.


Graph 2 (above): Sami’s second performance test at Stanford, coming off three months of devoted carb restriction and fat emphasis in the diet. Here, at 300 watts, Sami has doubled his fat oxidation to over 400 calories per hour, going from burning almost all carbs to about half carbs, half fat.


Graph 3 (above): Sami’s third performance test, on the heels of his amazing Clydesdale-style Wildflower victory, where he beat some of the nations best amateurs despite carrying 200 pounds (due to preparing for an interesting trip to Hawaii—details follow.) Notice the fat utilization at low intensity of around 85 percent of total energy and 750 calories per hour—triple that of the levels he delivered on his first test!

Sami’s successful transition to fat adapted athlete tee’d up one of the most remarkable endurance performances you will ever hear about. He and his wife Meredith Loring rowed a small boat from San Francisco to Hawaii—2,400 miles in 45 days. In the process, they raised $300,000 for the Institute of Responsible Nutrition, an advocacy group headed by anti-sugar crusader Dr. Robert Lustig. Because their journey was unsupported, Sami and Meredith traveled with some one million calories—ultra low-carb, high-fat selections like dehydrated beef, salmon, and vegetables, along with fruit, nuts and olive oil. Sami also lost 26 pounds on the journey, indicating that a combination of ingested fat and stored fat were his main fuel sources. A feat like this completely reframes the carb paradigm that endurance athletes have long existed in, whereby sustained endurance efforts were highly dependent upon successfully ingesting and absorbing a steady stream of carbohydrate calories. No, there was no bonking allowed aboard a twenty-foot rowboat in the middle of the Pacific Ocean! I don’t know how much more convincing you need to try ditching carb dependency and become fat adapted than this absolutely mind blowing data and enthusiastic message from Sami.

Check out our Primal Endurance Mastery Course to get the step-by-step guidance you need to achieve this objective without the high risk of backsliding and burnout that comes from an ill-advised approach. This online multimedia portal is the most comprehensive educational experience ever created for endurance athletes, with a robust video library of expert interviews as well as bite-sized video presentations that take you through the entire content of the Primal Endurance book. We also have a free sample video series so you know what your course experience will be like.

Note: After co-founding and selling the popular real estate website, Sami has embarked on a fantastic new venture as the CEO of Virta Health. They offer, “the first clinically-proven treatment to safely and sustainably reverse type 2 diabetes without the use of medications or surgery.” Their mission is to reverse Type-2 diabetes in 100 million people by 2025. Check out their cutting edge program.

Thanks for reading today, everybody. Let me know your thoughts below, and have a great week.

TAGS:  Keto

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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