Marathon training and Ketogenic Diet

I switched to a Keto diet for my upcoming marathon and this is what happened...


I am not a registered dietician and nothing in this post should be considered dietary/medical advice. I am a Certified Personal Trainer with a specialty in Sports Nutrition. Unfortunately, the only nutritional recommendations I am allowed to make follow the governments model…. and I refuse to do that so I refrain from giving any advice at all. The following is merely a long explanation of how I started eating this way and my experience compared to other ways of eating.

The whole topic of high-fat low-carb vs. high-carb/low-fat is very polarizing. There are die hard fans in each camp. It is hard to discuss nutrition these days without getting into a heated debate over which is the most optimal way to eat.

I like many people have been led to believe that a high-carb/low-fat diet was the key to optimal health. I have trained for numerous endurance events and used this model of eating with success. I have done everything from Mediterranian/bodybuilding to 80/10/10. The more research I did on high carb diets the angrier I became.  I will put some links at the end of this post- If you do enough research you can find links to support each side of the argument. Certain things are not secret like Monsanto (don’t know what the big deal with Monsanto is? – see links at end) and the Government, the FDA and the things they allow us to consume vs. what other Countries have banned. My wariness with the government’s role in our health grows with each passing year. I won’t get into a long rant but if you aren’t already, you should be cautious of any person/group who makes recommendations with something to gain i.e.: doctors/ Govt./Big Pharma… I’ll leave it at that.

Why I chose the Keto diet for my race: As I mentioned earlier, I have used high carb diets for long endurance events. This required many carbohydrate/sugar filled supplements during the course of a race: gels, jelly beans, liquid… I heard about a lot of ultra marathoners and professional athletes switching to this diet and the improvements they had with performance. Intrigued by the idea of endless energy without supplementation I figured what better time than now to give it a try?!?!

Keto Flu- Myth or Reality?: I read about the many horrible symptoms that people were experiencing while fat adapting. I guess I was one of the lucky ones because my symptoms were relatively mild. I had a very mild brain fog and felt a little more tired than normal the first week. There was a mild headache that I couldn’t shake for a week. My energy levels were lower than normal. I have read some horror stories and ways to avoid them. I credit my lack of flu symptoms to drinking a lot of water and upping my salt intake to keep my electrolytes in balance during the process. I pushed through the cravings and after a week, it was like a light switched and I had a crazy abundance of energy, totally clear mind. My mind felt so sharp. The whole experience was surreal.

Training while fat adapting: I won’t sugar coat this, training was a challenge. My energy levels were low and my body was not efficient at turning fat into fuel. This proved to be especially frustrating for someone training for a marathon! I also struggled mentally with the fact that the best time I ever ran a half marathon was 2:15 and not training for close to 3 years brought that time to 3 hours prior to switching my diet, to 3 hours plus after the switch!!! UGH! I feared that I would never get better and would have to withdraw from the race. My training really sucked for a good month. This had to be one of the most frustrating months of my life. I kept on and then something magical happened. I noticed running felt back to normal and I didn’t need to supplement with gels, never hit a wall, and felt like I could go on forever. When I do my long runs now I am still amazed by the fact that I don’t need to take energy gels. I remember the days when I would calculate how many hours I would train and how many calories I would have to supplement during a training session. I no longer have stomach cramps/nausea after a hard training session. The whole experience has been so liberating.

Benefits I have noticed

  1. You get a new found level of mental clarity, I never realized what kind of mental fog I lived in until I cut out the carbs.
  2. I wake up and don’t depend on coffee to get my day going, whereas before a while pot of coffee was necessary to get moving.
  3. I can run for hours on end without needing supplementation.
  4. My mood has stabilized, I no longer get “hangry” because I never feel that overwhelming need to eat like I did before.
  5. My energy throughout the day is very stable, I do not have highs and lows throughout the day, no afternoon crashes.
  6. I feel satiated at the end of a meal, in fact, there are times where I don’t feel the need to eat everything on my plate because fat is so filling.
  7. One of the most impressive benefits is the stabilization of my blood pressure- I have always had slightly elevated pressure and now my pressure reads normal if not better!

Negatives of the Keto diet Nothing is perfect and though this way of eating comes with some amazing benefits, it isn’t without its downfalls.

  1. Your body doesn’t hold onto water so you must drink more and also add a lot of salt to everything to keep your electrolyte levels stable.
  2. Eating out takes a lot more planning/thinking, you can’t just sit and eat pizza with friends, you have to order something else which always brings the same conversation until people realize you aren’t changing anytime soon.
  3. If you are an athlete, you can expect a major hit to your performance for at least a month. Even though the headaches pass, it takes a while for your body to truly become fat adapted.
  4.  Digestion/bowel movements can be tricky the first few weeks: ranging from constipation to liquid, depending on how your body adapts and what you consume.
  5. Cravings suck the first few days and you have to get creative to re-create your favorite treats.
  6. This diet lacks a lot of micronutritional content- vitamins are necessary. If you are an athlete you will definatley want to take a potassium/magnesium supplement to help with cramping!

Have you tried this way of eating? Curious? Have questions? I would love to hear from you.

I will do a post marathon follow up in a few weeks!

  1. Low Carb High Fat Success says

    I have tried the ketogenic diet with exercise, and it was tough for the first month. I felt dizzy most of the times and felt weaker. I think it was just my body adjusting.

    But after that month, I don’t crave sweets anymore and surprisingly have more energy far longer and my mood has also improved.

    1. Tina C. says

      The first month is the hardest! I got really nervous when I started working out because my performance dropped significantly during that period of time. Performance didn’t pick up for a few months because even though the initial fat adaptation happened… the true adaptation took a long time. It took my body a long time to work up to running a full 26 miles on just fat.

      It’s funny you mention not craving sweets, I don’t miss them at all. Savory fatty foods have always been my thing. The only sweet thing I crave is ice cream. I have found some amazing keto ice cream recipes :).

      How long have you been keto?

Comments are closed.

Subscribe For Latest Updates

Signup for my newsletter and get notified when I publish new articles for free!