Trigger warning: This piece tackles diet which has become an emotional issue for a lot of people advocating a certain way of eating. For full disclosure, I am neither a sports nutritionist or doctor and all that’s written here is based on my personal research and experience with various diets.

I start with a less controversial proposition: You cannot outrun a bad diet.

So if you came into running as a way of compensating for unhealthy eating habits, or worse, getting away with sugary or junk food, and even alcohol, then you are probably in for a disappointment.

It is well-established that genetics is not entirely determinative of an individual’s health and longevity. There are a number of levers one can pull to live a healthy, fulfilling life. Among these are diet and exercise. Based on studies though, it is more the former than the latter.

One reason is that the basal metabolic rate consumes 60 to 80 percent of the total energy produced by the body, which means that only about 10 to 30 percent of calories are lost through physical activity.

It is also not just the quantity of the calories that matter. The quality of the calories count even more.

Thus, the idea that one can eat whatever one wants for as long as he or she regularly goes to the gym or runs marathons, is a product of wishful thinking rather than science. Which leads us to our main topic: What diet is optimal for runners.

Runners and other athletes consume a lot more energy so, for a long time, it was thought they needed to constantly load up on carbohydrates (which the body metabolizes into glucose) to fuel their training.

And, on race day, they need to aggressively top up their glucose levels by taking sugary gels at least every eight kilometers of a run, otherwise, the runner is sure to bonk or hit the proverbial “wall.”

One of the proponents of this preference for carbohydrates was Doctor Tim Noakes, author of the Lore of Running, and who was himself an ultramarathoner.

In said book, he said, carbohydrates are particularly important for endurance athletes as they are the body’s preferred source of fuel during exercise. He spoke of the Energy Depletion Model, which predicts that when the body’s carbohydrate stores are depleted, the exercise intensity falls, because some limiting concentration of muscle glycogen is reached.

This model suggests that fatigue is basically inability to supply energy (adenosine triphosphate or ATP, mainly from glucose) at a fast enough rate, or a depletion in energy stores. When endogenous carbohydrate stores are depleted, fatigue occurs.

Thus, said Noakes: “Exercise performance during prolonged exercise of 1 hour or more can potentially be enhanced by increasing the amount of carbohydrate stored before exercise, by reducing the rate at which those stores are burned during subsequent exercise, and by ingesting carbohydrates in the appropriate amounts during exercise.”

At the start of my running journey, I took this idea of carbo loading to heart. Finally I had an excuse to eat loads of pasta, pizza and desserts. The result was disappointing, to say the least.

I constantly experienced sugar crashes and the more I ate carbohydrates, the more I felt I had to eat. This led to weight gain, mental fog, fluctuating energy levels, and fatty liver, among other things.

I also hated that, during races, I became so dependent on energy gels and could easily finish six packets in the course of a full marathon.

I was certain that if I continued on that path, I would have eventually become insulin resistant — if not diabetic, hypertensive, and prone to all other chronic diseases. Yes, despite all that running.

This led me to decide to change course, which was how I stumbled upon the ketogenic diet and, eventually, the carnivore diet, which I have been on for nearly six years.

Coincidentally, Dr. Noakes changed his mind too about carbohydrates.

After publishing the Lore of Running in 1986, he published the Lore of Nutrition in 2017 wherein he advocated for a low carbohydrate, high fat diet even for athletes.

His work and that of other scientists like Jeff Volek and Stephen Phinney show that it is the emphasis on high carbohydrate intake that prevents us from utilizing fat as energy source.

Using fat as a primary source of fuel is infinitely more efficient for athletes since even the leanest athlete will take days to deplete his or her fat stores but it will only take that same athlete hours to completely deplete his or her glycogen storage.

The problem is, as long as there is an abundance of glucose to burn, our bodies will prefer it as fuel and we can’t become fat adapted.

Hence, some endurance athletes like Zach Bitter and Michelle Hurn (also a nutritionist and author of the book, A Dietitian’s Dilemma) have transitioned to a ketogenic or low carbohydrate diet to achieve metabolic flexibility — i.e., make the body as efficient in using fat for fuel.

With proper adaptation, our bodies can become a lean, mean, fat-burning machine.

Since the shift, my energy has skyrocketed, mental fog is gone, SGPT has gone back to normal, lipid panel within ideal range, and I have never had to worry about excess weight.

There is a lot more nuance to unpack in this carbs versus fat for fuel issue. Stay tuned for future columns on the topic.