As an exercise physiologist I am always interested in evidence-based methods to improve my performance. However, many of the scientific principles that shape our day to day approaches to training are years behind the current thinking or simply wrong due to scientific dogma inertia. But its not the fault of scientists, entirely (I swear!!!). A rigorous controlled exercise study in humans requires a lot of resources. If the National Institutes of Health has the choice of funding a clinical study examining whether a given intervention improves exercise performance or whether an alternative intervention improve outcomes for patients with a severe disease the decision is obvious, and rightly so. Even when there are the resources to do exercise studies its immensely difficult. Noncompliant subjects, inherent inter-subject variability, expensive scientific equipment and small effects on performance (<5%) that are difficult to detect. Ok, rant over. Thats why I’ve decided to conduct my own n=1 experiment on myself based on less than gold standard level of existing evidence.
As ultrarunners a major goal of our training is to maximize the use of fat and minimize the use of glycogen during exercise. In essence we want to be “fat adapted”, which is really my goal for this little experiment. The science shows that at the same workload (ie running pace) if can either become more fit or consume a high fat low carb diet you can shift your body to use more fat relative to glycogen. So what happens when you combine the two? Well there are a number of athletes that already do this. One prominent example is Zack Bitter, a dedicated disciple of high fat low carb diet, who set the American 100 mile record (and world record for 12 hours) in late 2013 and fully believes that his diet played a role. However, the scientific data on high fat low carb diets improving performance are more equivocal; with the relatively few studies containing a number of caveats and nuances that make the interpretations difficult (which I hope to discuss at some later time). On the other hand the prosperity of the data on the health benefits of high fat low carb diets supports them (see here, here, and here). Add on top of that the amazingly good fasting blood lipid levels of high fat low carb ultrarunners Zack Bitter and Joe Uhan and I was ready to take a leap of faith.
I figured that while I slowly regain fitness with a deliberate build up in training it would be the perfect time to try this new approach. Of course, perfect is relative, and from a scientific point it would have been better to change only one variable (my diet) and not also my training (going from none to some). Still I think perhaps it might be advantageous to be on a high fat diet while I am improving my metabolic capacities and thus any new mitochondria I create maybe predisposed to use fat. Its a hypothesis, and unfortunately one that can’t be directly tested in an n=1 study on myself. There were other reasons to make the diet change. I want to prevent those carb binging situations that wildly swing my insulin and glucose levels and instead keep energy levels steady throughout the day.
I started by reading Phinny and Voleks “The Art and Science of Low Carbohydrate Performance”. Based on their expertise and the evidence I have started with a high fat low carb diet that 1) restricts carbs to ~50g/day, 2) does not restrict the types of fats I eat (butter for breakfast, lunch, and dinner please), and 3) try to maintain the same level of protein (~0.8g/lb) to prevent a backdoor formation of carbs through gluconeogenesis. The scientist in me wants to test, test, test. Most importantly I will regularly test my blood ketone levels. Its a relatively simple measurement that uses a finger prick worth of blood applied to a device that is the same as what diabetics use to track blood glucose. The goal is to be in nutritional ketosis, which is characterized by a blood ketone level between 0.5 – 5 mM. I have periodically tested myself during the adaptation phase (~2 weeks) and as I play with other variables (cheat day, carbs during workouts, etc) I will continue to donate blood to the cause.
As I continue this n=1 experiment I hope to share some of the results as well as dive a little more into the data and science behind the idea, hopefully to discuss past and future studies that shed light on a complex metabolic issue.