Experimenting With Life On The Edge Of The Paleo Diet (low insulin/high glucagon) As An Older Endurance Athlete

Author’s note, April 8th, 2018: For some reason somebody noticed this old article of mine. I bonked at mile 125, but did walk to mile 138 by midnight, on the edge of nausea if I tried to run. This was how I realized that older people who drop off late in the course are at risk. In August 2015, I went vegan. I’m now exploring that conundrum. But, to be honest, the only real challenge I face is aging combined with progressive vascular disease. Have fun, my friends, life is brief. See you on the course. kev aka FitOldDog

Hi folks! Welcome!

The Primal Blueprint by Mark Sisson

A truly great book, and well worth reading for anyone, athlete or no athlete, old or young, male or female.

If you read the current literature on the ‘Paleo Diet’ fad, and it is a kind of fad, but it has really solid biochemical underpinnings, best explained by Mark Sisson in The Primal Blueprint, you will find conflicting advice on how to handle endurance sports. So what’s to do? Experiment on yourself, as we are each unique, but highly similar, biochemically.

Based on my years of experience in biochemistry and large-scale gene expression, it became clear that we have two very different metabolic states, those being high insulin/low glucagon (fed state), and low insulin/high glucagon (fasting state). The so-called Paleo Diet takes you to the latter state, encouraging the burning of fat, with the benefits of weight loss, more attractive figure, no hunger pangs, and eating great food. I really like this diet. Then I thought, and maybe I won’t have to eat all those bars and gels in Ironman races! Great!

My experiments with the Paleo Diet and Ironman training resulted in one interesting finding (not new, apparently, but new to me): in order to stay in the fasting condition, burning largely free fatty acids and ketones, I will have to very carefully titrate additional carbohydrates needed to perform well, whilst not collapsing back into those insulin surges that can lead to bonking and weight gain.

FitOldDog's image of energetics

FitOldDog drew this highly simplified diagram of the fuel circuit required for the test-bed component of his last scientific publication – those were the days. Click image for link to article.

The data:

  • I managed to qualify for the 2013 Ironman 70.3 championships (but my times were off – red flag #1) on a purely Paleo-style diet – no carbo-loading, no food on the course. I felt fine, but ravenous after the race (red flag #2).
  • I crashed with irreversible nausea round mile 125 at the 2013 Lake Placid Ironman, and my swim and bike times were way off – again, only three eggs for breakfast at 4:00 am., and no carbo-loading or food on the course. Making it to mile 125 on three fried eggs is pretty impressive.

Conclusion: I will have to supplement with moderate glycemic index carbs during training and races, but how to do this without falling back into the old high carb, high insulin, metabolic state? That is the ultimate metabolic conundrum. It is at a place that is just on the edge of the fasting metabolic (transcriptomic) state, at the lower edge of the low insulin/high glucagon condition.

Paleo Diet for athletes FrielAnswer: read about other people’s experiences, and experiment on myself.

The experiment will continue at the 2013 Louisville Ironman in about a week, and under no circumstances do I want my 4th DNF!

Why am I doing this race so soon after Lake Placid, you might ask? Because I’ll be racing with my son, Nigel, and which dad in his right mind would miss such an opportunity?

-k @FitOldDog



  1. What do you think of the Hay diet?

  2. Excellent for cattle, especially dairy cows, as long as it is mixed with a little silage and protein concentrate for variety – yes, cows like variety.

  3. What about the Dr. Hay diet? http://en.wikipedia.org/wiki/Hay_diet

  4. hahaha, ‘hay’ diet. And, for the rest of us, please translate some of the science, like this word: (transcriptomic). What does that mean?

    • Explain transcripome: now, there is a challenge.

      Maybe I should write a primer blog post. This is a truly non-trivial challenge, but if I understand the subject I should be able to translate (the step following transciption as the DNA based code is passed along to the cellular machinery) the main concepts. Will give it a try as a blog post – an understanding of network behavior is also critical. Glucagon is a hormone, the details of which can be found on the web. To some extent it counteracts the effects of insulin (which does hundreds if not thousands of things), but, as usual, it’s not that simple. -kevin

  5. And glucagon.

  6. There was a recent experiment done on race walkers in Australia where they trained on a high fat diet. Race times suffered.
    But what was noted was that in the weeks after they left the experiment, many had their best times.
    So the moral may be to train high fat, race low fat.( high card)
    Sort of like the old train at high elevation and race at low elevations.
    Of course the trick may be to determine just how close to race that you increase carbs.
    Look up Alex Hutchinson, sweat science. He has a couple of articles about this.

    • Hi John,
      I enjoyed that experiment. People said I was crazy to attempt full distance on a few eggs in the morning, plus water and electrolytes. I did pretty well, considering my level of ketone adaptation and age. I trained almost pure Paleo for over a year before the race. If I remember right, I made it to mile 138 by midnight.
      The next day, a friend of mine said, “Kevin, it’s odd. You almost completed the distance, but you’re walking normally. You are even walking down stairs with no apparent discomfort. This was a truly interesting observation – less inflammation?
      I left Paleo, and went vegan a few years ago. This comes with other interesting challenges, though age is the greatest battle (75 this summer – damn!).
      We each have to work out what works for us with what we have left.

    • Hi John, it’s funny how this article was suddenly noticed. I think I wrote another, about my Cori cycle being unable to keep up with my bi-cycle (biochem joke). I left science in 2010, not that one ever does, and I now I make my living as a story-teller, to help older people cope with the changes. Aging is tougher than an Ironman, and no medal, water bottle or space blanket. I plan to do Ironman for as long as my body permits. Enjoy it, my friend, cheers, kev

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Disclaimer: As a veterinarian, I do not provide medical advice for human animals. If you undertake or modify an exercise program, consult your medical advisors before doing so. Undertaking activities pursued by the author does not mean that he endorses your undertaking such activities, which is clearly your decision and responsibility. Be careful and sensible, please.