- We are Running on Ketones. This is not a typical story; we are endurance athletes at different stages of our lives, who are experimenting with a low carb Ketogenic diet. We are not doctors or scientists, just athletes. Anthony is the youngest and the fastest, age 20, and prefers ultra road running. Eric (ZoomZoom), age 27, is ukulele playing mixed distance runner. Dan (SKA Runner), age 42, is new to running, prefers mountains ultras, and a bit of a computer geek. Bob(uglyrnrboy), age 54, prefers mountains ultras and loves to tele ski. This site,, will document our journey as endurance athletes implementing a low carb ketogenic diet in to our lives. Please feel free to contact us with any questions you have about our experiences.

What is a Nutritional Ketosis Diet? []

The ketogenic diet is a high-fat, adequate-protein, low-carbohydrate diet. The diet forces the body to burn fats rather than carbohydrates. Normally, the carbohydrates contained in food are converted into glucose, which is then transported around the body and is particularly important in fuelling brain function. However, if there is very little carbohydrate in the diet, the liver converts fat into fatty acids and ketone bodies. The ketone bodies pass into the brain and replace glucose as an energy source. This elevated level of ketone bodies in the blood is a state known as ketosis.


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Breaking Through the Keto Flu (First Two Weeks on a Ketogenic Diet)

AnthonyWhen I made the keto switch I had been on a high-fat, moderate-carb diet for about two years, and had also experimented with fasted running. But I still had to put up with the Keto Flu...

From my personal website back in August:
"I'm taking in less than 50 grams of net carbs (carbs-fiber=net carbs) a day, as well as limiting protein consumption to less than about 150 grams a day, in order to force my body to run entirely on fat. I don't know of any ultra runners who restrict carbs to this extent so its going to be a great experiment.
My only concern is that the lack of carbs could effect my speed since fat requires tons of oxygen to be burned while carbs can be burned without oxygen (anaerobically) during hard sessions. As someone who enjoys speedwork and shorter/faster racing, I don't want my diet to limit me.

Last Monday, on day four of my ketogenic diet I did a 20 mile trail run at Bear Creek Lake Park in Lakewood, CO. The previous day -day three- had been rough, with moodiness, low energy, and a general feeling of fogginess. So going into the 20 miler I wasn't exactly excited, but I was hopeful: since I had been out of blood sugar for a few days now I should already be past "the wall." And it turned out great. There was a definite low point from miles 4 to 6, but it wasn't bad and when it passed I felt strong until I finished.

I'm not sure why, but the next day -day five- I slept until noon and woke up feeling like I hadn't slept in three days. The entire day was spent in a heavy fog, similar to a bad fever. After an easy run my energy was back enough to feel like I could make it through the rest of the day without passing out. Day six was slightly better but I still didn't feel very coherent until after some miles. Day seven brought 24.5 miles over two runs and I felt great for both of them. On day eight I wrote "no more fog" in my running log and I felt like I was back. Day nine and ten were both above 20 miles and no crash followed like after day four.

It's now day 13 and I can feel the affects of running 100 miles last week while also forcing my metabolism to undergo a major change. However, my running pace has quickened over the the last three days with no additional effort on my part and I think most of the fatigue I have is psychological.

As a side-note, I think my brain operates better on ketones than on glucose: my attention span seems longer and I feel like I could read an entire book in one sitting -and actually retain 100% of it. I'm starting to feel like Bradley Cooper in Limitless.

The true test will come next month, when I race a 55'ish mile race, then an 8.6 miler the following weekend, then a 50 miler two weeks after that."

A quick summary of how it all tuned out: I did read an entire book in one sitting (What Happy People Know by Dan Baker, great book!), the races went amazingly, and I haven't had symptoms like those since.
I believe, based solely on my own experience and logic, that running shortens the adaption time. Since your body must first run out of glycogen before it even attempts to fat-adapt it makes sense that getting rid of your remaining glucose with some running would hasten the process.
We'll have a post up soon with the lessons learned from our adaptation periods that could help your adaptation go smoother.

How horrible or painless was your adaptation period? How many days was it before you felt normal again?


  1. I never experience the 'Keto Flu' as far as I know. The first week I sat up fast once and felt a little woozy, so I assumed it was coming, but I drank a lot of water and that was that. I also figured I was dehydrated. ???

  2. I have been trying on and off to run on Ketosis. Some weeks ago I went through some painful days. I had the keto-flu, all bones and muscle hurting at the same time, but I did not gave up, on my 6 day I was able to run again and I did my best 10k - 39 min (5 min less than my best previous one), I felt so much energy, I was running about 15-20k everyday even after working hours. I confess I relaxed durin the weekend and return to keto on Monday, but I felt worse the the previous time. I could not even go up and down stairs without feel like dying, 0% energy level, sleeping very bad and craving. I could not run this week and I decide to increse my cabs intake to about 30-40g a day. I feel a bit shame, I could had been more strong, but since I am vegetarian, I do not have so many options/variety of food to eat and I try to stick with fats.

    Well here I am reading about your experience and planning to start from scratch again.