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Gia Dawn Madole and Wendy Tremayne breath testing at the Colorado 200

Last week an unusual event took place in the Rocky Mountains of Colorado. It was a 200 mile foot race that has a 96 hour cut off time. A dozen people finished the entire 200 mile distance in under four days. I went out and paced my friend Rick (Hack Yourself to Run 200 Miles)  for the last ~68 miles. My interest in this event is how it pushes the envelope for what humans are capable of.  I brought along a home made ketometer to breath test the runners, pacers and crew at the event. The results are interesting, but the samples are limited so only observations can be made.


The idea was to get a sample from each runner to determine the level of acetone on their breath. A high acetone reading indicates that the runner is in ketosis and able to burn fat. A lower reading would indicate that the runner is not burning much fat and is fueling primarily on carbohydrates. Runners in ketosis blew in the range of 500-625. Those with readings of less than 500 were likely fueling on significant amounts of carbohydrates.


The data indicates some trends:

  1. Diet – The highest fat burning readings recorded were from people on a LCHF (Low Carb High Fat) diet. There was a surprise when we found two people blowing higher numbers who were not on a LCHF diet. Those two people were on a reduced calorie diets. They became good fat burners by not eating enough food each day.
  2. Performance – My suspicion was that the LCHF would perform the best. That was not the case. The top two finishers (tied) Travis and Douglas who are both very accomplished athletes were blowing readings below ketosis level. The women Sylvia Greer that finished after them in 2nd place was an excellent fat burner blowing higher than all the other female runners.
  3. Race Like You Train – Talking to the athletes gave a clear picture of who had an “enjoyable” race and who suffered through their 200. There were two runners who broke from their usual ways of eating and did the opposite. One always ate LCHF, but changed to high carb during the race. Another always ate high carb (gummy bears and gels), but was not eating frequently enough. Both of these runners had very difficult races due to low energy and stomach problems. Multiple runners had commented that they tried a new product from an aid-station table and lost their stomachs for several hours after that.

Mikey Sklar and Rick Arikado at the Colorado 200 mile ultra race

A race like this becomes a foot and belly race. Make sure you feet are feeling good by way of blister management, hot spots and dry shoes. Keep the belly happy by eating foods that you know work for you. I would eat eggs, avocado and ham for breakfast with a dinner time avocado burger. The rest of the time I lightly snack my way through at less than 50 calories an hour. This made for a comfortable fueling strategy. I was fortunate to completely avoid foot and belly issues at this race.