This is the fifth and final post in a series of guest blog posts written by David about his journey through understanding metabolic efficiency. Enjoy!
How All of This Ties to the Athlete
From an athletic perspective, the body will use a combination of fats and carbs when exercising.
What combination depends on the intensity of the exercise, the specific muscle fibers recruited to perform, and, of course, each individual athlete. If you have to sprint away from the lion, you are going to operate at an extremely intense level (very high heart rate) and therefore the body will recruit fast-twitch muscle fibers to complete the task. This extreme level of exertion can only be held for one minute, maybe two, and (generally speaking) will use 100% carbs for energy. This is by design as carbohydrate burns very hot and very fast. Fast-twitch muscle fibers lack the amount of mitochondria (energy source of the cell) of slow-twitch fibers to utilize oxygen for energy generation.
So when you are sprinting away from the lion, the body cannot recruit slow-twitch fibers, because the oxygen intake (you barely breathing as you scream away from the animal) is not sufficient. Conversely, when you go out for a jog, and your heart rate is lower because you are not being viewed as dinner. Your body will recruit slow-twitch fibers, and you will burn mostly fats for energy. Fats burn very slow compared to carbs. Your heart rate (literally your heart pumping blood through your body) will is a huge factor in determining when your body crosses over from using its aerobic system (slow-twitch) to anaerobic (fast-twitch).
The trick for me, and numerous other athletes, was to retool my diet and training so as to allow my body to run off of its fat stores, versus the fleeting carb stores, via dietary changes, and change my training so as to increase the amount of work I could perform while keeping my heart rate in the “fat burning” zone. As an example, I ran a 50K in January while keeping my heart rate below my anaerobic threshold. I still burnt out at Mile 18 and needed to chug sugar for the next 12+ miles. I had not yet acclimated my body, via dietary changes, to recognize my stored fat as an energy source.
Now that I made that change, I can go out and run 18 miles, at a faster pace than in January, all while burning fats, and never need a drop of carbs. In fact, I often do so in a 12 hour fasted state with nothing more than 12 ounces of water. This is the idea behind metabolic efficiency as it pertains to athletes. It is worth restating that there is a place in the diet for the right kind of healthy carbohydrate. For me, at an increased training level, that amount seems to be around 100 grams of carbs per day. My multisport career is very young, but, after 4 months of these changes, I can perform more efficiently than ever before. I am faster, for longer. Another advantage I notice is that my recovery time dramatically decreased. It makes sense. If you are operating at a lower “intensity”, you are not hammering your muscles as hard.
For all of you 100m sprinters out there, operating exclusively using fast-twitch muscles, you very well may need a higher amount of carbs. I know some that do, I know some that don’t. We can all trot out examples of outliers, or exceptions to the norm. But the concept behind metabolic efficiency for an athlete is simple, train your body to do more work while remaining in a fat burning state (lower heart rate), and eat a diet that allows your body to recognize fats as the primary source of fuel.
From a general health perspective, the concept is much easier. Ever see an animal in the wild count calories? Nope. So why would we? No other animals in the wild suffer dramatic changes of health unless and until you alter their diet or habitat. Why would we be different? Giving your body a chance to efficiently regulate itself by eating a high quality, natural (unprocessed) foods diet is a healthy decision. What foods you choose to make up your macronutrients (and micronutrients) is up to you. But whatever you do, stop listening to the noise about a magic bullet diet pill or 3 day juice cleanse. Take a look at the gun instead, and it will tell you what ammo it needs. For eons it told us everything we needed, and now it may be telling us everything we don’t need.