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Demystifying Keto, Part 2

Keto for High-Performance Athletes


Click here to read Part 1

The Keto Diet (KD) is certainly mainstream, but there is still a lot of misinformation floating around—especially about athletic uses. You hear about it everywhere. Articles, magazines, people in line at the store, your friends—they’re all talking about it. In “Demystifying Keto, Part 1,” I explained the basics of the KD, what a ketone is, how the KD ties into our historic eating patterns, why weight loss occurs on the KD, what “Keto Flu” really is, and why I think hunger isn’t as bad as people think it is. In this article, we’re going to tackle how the KD applies to you: athletes who work out so much that normal people put them on the spectra of “insanity.”

What about athletic performance?

Dr. Dominic D’Agostino is a Ph.D. ketogenic researcher at the University of South Florida. He is also a powerlifter. I have read, watched, and listened to him at length and he outlines numerous ketogenic diet studies in athletes. Short-term performance studies in athletes have shown reduced performance, but it can take months to be fully keto-adapted. The FASTER study, performed by Jeff Volek, showed that keto-adapted athletes had fat oxidation enhanced by 200%. This means we are much more adept at burning fat, and liberating more energy!

As we look critically at what we eat, we must also look critically at how much we exercise. Many of you are on the right side of the bell curve. And it ain’t at all natural. (Just my opinion.) Regular intense exercise is unnatural, but I still do it. It makes sense, as Dr. D’agustino suggests, that perhaps upwards of 150 grams of carbs per day might be better for heavy cardio. This represents relatively low carb eating. The degree of ketosis this would result in is debatable and would need to be measured. High-level ketosis will likely not occur, but being on the ketosis spectrum is possible given the athlete’s likely efficient fat-burning abilities, low insulin levels, and high insulin sensitivity. Especially with fat and ketone salt supplementation.

What about being a Hybrid?

Is a mostly carb-adapted individual still able to use ketones and fatty acids more efficiently for fuel? Many experts would suggest that this is achievable and should be a topic for future studies. Minimizing carb and being in a ketogenic state during most of the day, reserving carb sources for exercise, is suggested by many as being the best of both worlds.

The focus being to relegate carb to its proper timing, such as before, during, and after workouts, when it’s more likely to be utilized for energy and less likely to spike blood sugar (which then spikes insulin and leads to a myriad of metabolic consequences).

Many KD “experts” will suggest consuming 10-40 g of carb per day. Most of these folks, however, are less active than many of you reading this today. Although high-level endurance athletes that are fully keto-adapted can destroy it at these low carb intake levels, most athletes will perform much better at up to 200 grams of carb per day. Throughout the day, ketosis can still be maintained. And this still represents much less carb than what has been standardly advised.

For most individuals, properly timed carb intake will result in better workouts and the ability to go longer and faster. When you look at the effects of long-term elevated blood sugars and insulin levels, it’s clear that these largely-preventable physiological states drive disease. With their resultant damage, it behooves us to ask ourselves just what in the hell are we doing.

A recent case study details the experiences of an elite triathlete who fueled with 60 g/hr of carbs during high-intensity training.He/she experienced meaningful performance improvements, event though he’she had consumed a low-carb high-fat diet for over 2 years.1

The genesis of carbs and the premier endurance fueling diet

A KD as endurance fueling represents a radical paradigm shift from “carb is king” thinking.

High carb dieting as a necessity for exercise performance gained credence in the late ’60s, when it was discovered that glycogen depletion caused fatigue and high-carb consumption maintained glycogen stores.2

Massive evidence has accumulated supporting this practice, resulting in entities like the Gatorade Sports Science Institute (GSSI). The supremacy of the high-carb fueling paradigm for performance maximization has been indelibly etched in many minds. But by the late ‘60s, Dr. Cahill was coming to understand the human machine’s robust capacity to adapt to low or no dietary carb availability.3 He discovered that through well-preserved mechanisms lipid-based fuels supplanted glucose, through ketone production as a brain fuel and fatty acids for skeletal muscle. Now decades later, we’re trying to reconcile all this, while facing bias and dogma.

The GSSI recommends that in the 24 hours before hard training or competition athletes should consume 7-12 grams of carbs per kilogram of body weight. Let’s do some math . . . for a 150-pound athlete, that is 477-816 grams of carbs, or about 50 slices of bread. That does not pass my DIMADS test—in fact, it’s lunacy. I heard recently that Oscar Mayer and Mountain Dew are also starting their own sport science institutes…

Power to Weight buzzword

Much of success in sports involves the optimization of your power to weight ratio . . . enhancing power and muscle efficiency, while minimizing unnecessary weight.

Dr. D’Agustino, a powerlifter himself, determined that there was no muscle loss in his weight lifter ketogenic eating test subjects. These lifters consumed upwards of 85% fat and very low amounts of carb. They experienced an increase in muscle hypertrophy and power and a reduction in percent body fat. This “leaning out” process optimizes the power to weight ratio. From a primary care perspective, this results in a dramatically enhanced quality of life, less medication, less hospitalization, and greater independent and functional longevity.

F.A.S.T.E.R. study

Dr. Volek et al. performed the Fat Adapted Substrate Oxidation in Trained Elite Runners (FASTER) study that was published in Metabolism in 2016.4 The purpose was to study the extent of metabolic adaptions and differences between high carb eating athletes and low carb, high-fat eating athletes. It involved 20 elite ultra-marathoners and Ironman distance triathletes, all in “racing condition.” Over half of them had sponsors, a third of them had course records, a fourth of them participated for Team USA, and some had national and international records. Through an extensive interview process, 10 carb eaters were found (carb:protein:fat ratio being 59:14:25) and 10 fat eaters were found (10:19:70). The two groups were very closely matched in every other category except diet and fueling practices. The low carb group consumed six times less carb during an average day than the high carb group (82 vs 684 g/day). What is very important to understand is that the low carb eating athletes had been doing so for an average of 20 months, thus they were considered fully keto-adapted.

Despite the two groups being considered closely matched, there are some interesting small differences between them:

% body fat 9.6 7.8
Lean mass, kg 57.3 60.9
Fat mass, kg 6.5 5.5
VO2 max 64.3 64.7

From the above data, what observations can you make about the power-to-weight ratio?

Fat oxidation was 2.3-fold higher in the low carb group (1.54 g/minute vs 0.67 in the high carb group). Despite the marked differences in fuel usage, there were no significant differences in resting muscle glycogen, exertion related glycogen depletion levels, and glycogen re-storage levels in recovery. Restated, the low carb athletes possessed an extraordinarily high rate of fat oxidation but exhibited the SAME glycogen utilization and repletion patterns as the high carb athletes.

Several previous studies did not show preserved glycogen stores in low carb athletes.5,6,7 These studies in general observed athletes consuming low amounts of carb for a much shorter period, indicating that the cellular mechanisms and metabolic pathways involving glycogen preservation and restoration take a longer time. Full keto-adaptation takes at least several months, not weeks.

Dr. Volek likened the muscle glycogen responses in the low carb athletes to that of “Alaskan sled dogs.” These animals have tremendous endurance abilities and have been shown to maintain their glycogen stores despite running 160K per day for five days and eating high fat and only 15% carb.8

It’s important to realize that the FASTER study did not measure performance. Important future work would include studying truly keto-adapted athletes in regard to numerous strength and endurance measures.

For the first time, the FASTER study showed that well keto-adapted ultra-endurance athletes possess a dramatically enhanced ability to oxidize fats while maintaining normal skeletal muscle glycogen. Practically, the observations, in my opinion, lend credence to, and offer a viable rationale for, other dietary options available for endurance athletes. Dr. Volek states “Keto-adaptation provides an alternative to the supremacy of the high carbohydrate paradigm for endurance athletes.”


I was a carb eater and an excessive carb fueler. It’s what I was taught and what represented orthodox sports nutrition advice. I had 10-12% body fat, felt pretty good, and pushed it extremely hard. My innards were not too thrilled, however. This did, at times, assist in putting distance between me and all those behind me, but it didn’t take a genius to realize something wasn’t right. I came to accept a period of physical and mental bonking, was always sore, and had nagging injuries. I also accepted eczema, acne, and excessive phlegm as just being a part of who Bayne French was. Years ago this all changed. I remember looking at my breakfast plate of eggs, meat, and sautéed spinach at Mother’s Bistro in downtown Portland and feeling a sense of freedom, excitement, and empowerment at the absence of hash browns, pancakes, and toast. Over time my body fat percentage dropped to 7% and strength increased, as did stamina. I employed a “hybrid” strategy of LCHF living and reserved carb fueling via Perpetuem® to training and competition. This resulted in a 2016 second-place finish at the Spartan World Championships Ultra Beast Masters division in Lake Tahoe. It was a God-awful, nasty, brutal, austere mountain torture chamber of wind and cold, and I was never happier. Oh, and my skin, bloating, bonking, toots, phlegm, and injuries were dramatically better.

I want to perform at my best (at work, as a parent, and as an athlete), feel my best, and continue to do so for my entire life. I caution against making broad-stroke assumptions. Instead, come to understand what adaptations occur over time in response to LCHF eating and determine for yourself if those merits warrant experimentation. Maybe it’s time for a paradigm shift in your diet. Take a look at what you’re eating, how it makes you feel, and think about what you need to do to perform at your best.

References available upon request


Are there any resources on how much a particular athlete should ingest prior to, during, and after or is it all experimental based on each person? I’ve started down this path and for the moment have only been taking carbs (10-15g) post workout to see how it affects my ketone levels. Only being 7 days into this, they fluctuate quite a bit throughout the day and certainly after more intense sessions (though still not very intense because it’s currently “off” season for me). I know this takes time and will continue to monitor over the coming weeks/months. Just curious of a good reference to get me going in the right direction! Thanks for this article. It made a couple of things clearer for sure.
Hammer Nutrition replied:
Hello Debra, Thank you for your comments and questions. I’m not aware of a 3rd party resource, but I’ll give it a try. We recommend starting exercise from a fasted state meaning you’ve not eaten within 3 hours. Caloric intake of 10-45 grams of complex carbs per hour while exercising. Exercising with no calories should be limited to very easy pace and durations of 1 hour or less. Then consume 3:1 ratio of complex carbs to protein immediately after exercise to minimize recovery or wait 60-90 minutes post workout if additional fat burning/weight loss is desired more than speedy recovery. It takes most people 4-6 weeks to become fully adapted, so you are still going through that phase and ketone levels should increase and stabilize over the next several weeks. BDF

Debra Wechter

Thanks for the articles on “hybrid” keto. I have been moving to a mostly meat-based diet and have found that without carb supplementation I can’t perform at my peak (such as it is). The more carbs I eliminated the less I thought Keto would work for me, but this approach makes sense. I want to transition to Keto, can you recommend a place to start? I get the idea, but it seems there is a lot to learn and also a LOT of misinformation.
Hammer Nutrition replied:
Hi Bill, Thank you for your comments and questions. As you have experienced, it’s no fun to exercise with no carbs. As you’ll read in an upcoming blog article, I’m very much not a fan of diets that do not allow an abundance leafy, green and cruciferous vegetables (more on than in my good carb/bad carb article to be re-posted soon. The discussion here is definitely about moving away from Keto dogma and strict adherence to a hybrid low carb (read very little sugar, glutenous grains, starchy vegetables and fruit) – higher fat/protein diet. From where you are, it sounds like increasing fat intake (avocado, raw nuts, olive oil, etc.) and adding the aforementioned vegetables back to your diet will get you most of the way to your goal dietarily. Next, begin practicing light fueling during exercise (100-180 calories per hour, depending on intensity) from complex carbs and you should be a happy camper. BDF

Bill Summers

Love the summary Frenchie! “hybrid”, what a novel concept.

john cavoulas

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