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The Ketogenic Diet Revisited


Over the past couple of years, there probably has not been any diet more widely adopted or hotly debated than the ketogenic diet. In issue #114 of Endurance News, I wrote an article titled “Five Reasons Why We’re Anti-Ketogenic Diet.” Since that time, there have been numerous proponents of this diet, with at least an equal number of detractors. For someone (me) who relishes research findings and details, these research-based pros and cons have been most interesting.

Before I go on further, I want to first say to athletes who have been following this particular diet for athletic performance gains and have obtained noticeable improvements in their workouts and races: far be it from me to detract from those results. And if you tried other methods to improve the quality of your workouts and enjoy better race results but didn’t succeed until you adopted the ketogenic diet, then I would certainly apply the “if it ain’t broke, don’t fix it” rule.

That said, I still believe this particular diet yields the majority of its benefits in weight loss and not as many in athletic performance. You will get arguments from both sides regarding the ketogenic diet’s efficacy and safety used long term—I tend to think that it’s not the healthiest diet around when it’s adhered to too strictly and/or for too long. As I mentioned in my article in EN #114, “In fact, a panel of health experts recently evaluated 40 diets for several factors, including ease of adherence, nutritional value, safety, effectiveness for weight loss, and protective benefits against diabetes and heart disease. Their rankings were published in U.S. News & World Report, and the ketogenic diet was ranked near the very bottom in a tie for 38th.”1

Still, what I have been noticing—albeit fairly casually—is that some people are enjoying weight loss by following this diet. However, I believe that once that goal is achieved via the application of this restrictive diet, a modified ketogenic diet is in order, both for enhancing athletic performance and for overall health. While acknowledging that Dr. Bayne French and I don’t necessarily see eye-to-eye on all aspects of the ketogenic diet, we very much agree on these points:

  1. Carbohydrate intake during exercise and immediately following is essential.
  2. A less-restrictive approach to the ketogenic diet (i.e., consuming more than 50 grams of carbs daily) will yield results.

Carbohydrate intake during/following exercise

I like to quote Dr. Rick Kattouf, who states, "Not only do carbohydrates provide energy for working muscles, they also assist in enabling fat metabolism. In short, carbohydrates need to be present for fat to be utilized for energy."2

Additionally, research has shown that when carbohydrate levels are low, a substance known as pyruvate—which is formed during glucose metabolism—is unable to perform its job in the process of creating energy using oxygen (i.e., cellular respiration). When pyruvate is unable to perform its tasks—which it can only do in the presence of carbohydrates—the body’s ability to use fat as a fuel source significantly slows down or halts altogether. This same research shows that without replenishment of adequate amounts of carbohydrates, the body will cannibalize specific amino acids (BCAAs, alanine) from muscle tissues, which not only slows down metabolism, but also causes excess production of fatigue-causing ammonia.3

Dr. French and I are both on the same page regarding carbohydrate intake and timing. We need carbohydrates to fuel our bodies during exercise and to permit the vast amounts of calories from fatty acid stores to be used efficiently as an energy source. I didn’t come up with the saying “Fat burns in a carbohydrate flame”, but I firmly believe it and have used it frequently when consulting with athletes.

I also firmly believe that we need carbohydrates following exercise—both immediately afterward and in the next couple of hours (at least)—to kick-start the recovery process. One important aspect of that process is the restoration and increase of muscle glycogen stores.

A less-restrictive approach to the ketogenic diet

I completely agree with Dr. French, who wrote in an article titled “Demystifying Keto” in Endurance News, issue #121: “People who avoid ALL of the common carb sources listed above are most likely eating less than 50 grams of carb per day. It’s an important place to be if your goal is to produce ketones. Being in this sub-50 club is considered very low carb and may not be sustainable for most endurance athletes. Eating ‘good carbs’ that put you in the low carb range of 50-150 grams per day is a good long-term strategy. Many find this to be the sweet spot for athletic performance, palatability, and sustainability. Ketones will still be made in these carb ranges, especially if you’re supplementing fat and ketones.”

Good Carbs

High-quality carbs provide a wide range of nutrients, including health-promoting plant chemicals called phytonutrients. Fiber helps to slow the digestion of sugars and starches, thus preventing large spikes in blood sugar and insulin associated with diabetes, heart disease, and weight gain.

  • Broccoli
  • Cauliflower
  • Kale
  • Brussels sprouts
  • Strawberries
  • Raspberries
  • Blueberries
  • Blackberries
  • Walnuts
  • Almonds
  • Chia seeds
  • Pecans

My take on carbohydrates and their restriction

Dr. French makes some strong points about carbohydrate intake on pages 18-21. My take on them is as follows:

  1. Carb intake is about timing, with pre-, during-, and post-exercise carbohydrate consumption (especially the latter two) being imperative for enjoying high-quality workouts and races, and for supporting enhanced recovery between.
  2. I believe the best way for athletes to enjoy the athletic performance benefits that the ketogenic diet appears to have is to modify it for a daily intake (aside from exercise) of 150-200 grams of carbohydrates.
  3. While taking into account the semi-lengthy time that full glycogen restoration requires, we need to be extremely mindful of carbohydrate intake throughout the day, especially high-glycemic-index carbs. We can’t just be unrestrained carboholics—the health issues associated with that are numerous and undeniable—and a 150-200-grams-per-day amount is doable for most athletes.

Final thoughts

I’ve never been a fan of dieting—at least not in the purest sense of the word—while training. Though I most certainly feel that being aware of what we eat in our daily diet is undeniably important—as we’re fond of saying, “the calories you consume always matter”—I feel that following a highly restrictive diet plan for any notable length of time is not compatible with athletic performance. To me, the training we do IS our way of dieting and maintaining our desired weight.

That said, while there may always be a healthy number of pros and cons regarding the ketogenic diet, a modified approach—permitting the intake of more grams of high-quality carbs, but not an unlimited amount, and certainly not “junk carbs” (processed foods, sugar, etc.)—may prove to be the key to both improved athletic performance and much better health.

References available upon request


Steve what is simplest way to measure carbohydrate intake to conform to a modified keto approach???
Hammer Nutrition replied:
Hello R,

First of all, both Dr. French and I—and most certainly Brian as well—do not advocate the restriction of carbohydrates during exercise or immediately after… these are absolutely crucial times when carbohydrates are needed.

In my article, I used a portion of Bayne’s original article, which I feel is valuable information:

People who avoid ALL of the common carb sources listed above are most likely eating less than 50 grams of carb per day. It’s an important place to be if your goal is to produce ketones. Being in this sub-50 club is considered very low carb and may not be sustainable for most endurance athletes. Eating ‘good carbs’ that put you in the low carb range of 50-150 grams per day is a good long-term strategy. Many find this to be the sweet spot for athletic performance, palatability, and sustainability. Ketones will still be made in these carb ranges…

There are a Number of websites that will provide carbohydrate content for many food choices:

I personally would not expand too much energy measuring out and counting each and every carbohydrate that’s in each and every carbohydrate source… that kind of takes the fun out of eating. As long as you are fairly close in terms of carbohydrate intake your body will perform as you want it to.

Sincerely -


R Grace

Talk to athletes who have been invited to Olympic trials, on the Olympic team, International Iron man and woman invitees and see what they say. My physical therapist is one of them and NOT in favor of KETO as presented to public.
Your article was excellent!


Very well articulated, Steve. This topic needs to be viewed through a nuanced lens, where the optimal performance goals are achieved through hitting the middle ground of macronutrient consumption. Though life is easier when things are black and white, it just isn’t reality!

Brian Miller

Great information. This confirms my thoughts and approach to low carb diet and endurance exercise.

Tim Leech

Thank you for sharing your insights and research.
How would specific numbers and advice differ if you were writing exclusively for an audience of endurance athletes over age 60.
Hammer Nutrition replied:
Hi Terry, Steve asked me to field this one. Thank you for your comments and support. Since most of our clients are at least over 40, we are generally writing to this audience and our recommendations reflect that (younger athletes will have a competitive advantage and enjoy better health the sooner they adopt these dietary habits). In general, as we age the quality of our diet is increasingly important and we can tolerate less toxins, like sugar. Due to pancreatic fatigue, this is also when the slide towards hypoglycemia and type 2 diabetes kicks into high gear, as our pancreas is getting warn out. So, the 40,50,60 + age athlete will gain most by following these numbers – .5 to .75 grams of protein daily. .5 to .75 oz of fresh water daily, separate from what is consume while training and any other beverages. Filling out the diet with healthy fats and tons of vegetables (high water content, leafy green, cruciferous), while limited or eliminating sugar and starchy carbohydrates is definitely ideal for your audience. BDF

Terry VanderWert

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