As a health and running coach, I'm always up on the latest research. And one hot topic for runners in the past few years has been moving to a diet with an emphasis on metabolic efficiency. Rather than the standard high-carbohydrate, low-fat diet traditionally recommended for runners, metabolic efficiency emphasizes nutritional and training tweaks to teach the body to burn fat and carbohydrates more efficiently.
In short, the diet emphasizes more protein, more fat, and fewer carbohydrates so that the body becomes more efficient at fat burning.
In training, this means going for a long run without fuel or doing morning runs in a fasted, glycogen-depleted state to force the body to adapt and become less dependent on sugar as a fuel source. It sounds good, right? I suspected that I was a bit too dependent on carbohydrates for fuel and wanted to experiment with this theory for myself. Here are the results.
My sugar cravings subsided quite a bit, my body composition shifted (more muscle), and I gained a few pounds while getting a bit leaner. I did most early morning short runs in a fasted state and could do two-plus-hour-long runs without missing the fuel.
And here were the cons:
My racing did not feel as strong. I lost my ability to have a "kick" at the end of a race, short or long. Even with a few days of carb loading pre-race, I didn’t feel that I had the same force that I’ve had in the past.
However, my times did steadily improve—but that could have had something to do with more consistent training or metabolic efficiency practices.
It's all about the balance.
Now that I’m about two years in, I appreciate what metabolic efficiency has taught me about how my body works, but I’ve realized that I can find a balance. I’ve slowly been increasing the carbohydrates again so that I average closer to 50 percent of my daily intake from carbohydrates.
This is less than the 60 to 70 percent I was getting several years ago, but more than the 40 percent when I was more strictly following the metabolic efficiency guidelines. Did you know that sometimes increasing carbohydrates can encourage weight loss for runners? I’ve lost the few pounds I had gained and feel my energy back for a final push in workouts.
There are many benefits to teaching your body to work a little harder with less fuel, but this creates a lot of stress on the body and should not be used week after week as I did for a period of time. As with all diets, I believe everything depends on the individual. Someone who metabolizes meat very efficiently as a fuel would do better on a metabolic efficiency diet, while plant-based eaters would struggle to get the correct balance of protein to carbohydrate and would have to supplement their protein.
Going forward, I’m recommending that my clients find a middle ground!