July 20 2018
Whether you travel to your destination race by car or plane, here’s how to keep your pre-race nutrition on track.
Unlike fat and protein, carbohydrate is, for the most part, not used structurally in the body. Instead, it serves almost exclusively to supply cells with the energy they need to carry out important functions such as muscle work. Fat and protein can supply energy as well, but carbohydrate does so far more rapidly, making it the body’s go-to fuel for intense activity.
It’s no wonder, then, that piles of scientific research have shown runners and other endurance athletes perform better when their carbohydrate intake is higher. A few years ago, for example, researchers at Liverpool John Moores University tracked the diets of 257 runners during the final five weeks before the London Marathon. Those runners who ate the most carbs during this period completed the marathon on average 13.4 percent faster than the rest, irrespective of gender, age, body weight, training volume and marathon experience.
How much carbohydrate is needed to maximize endurance fitness? There’s no science-based formula that runners can use to determine their individual needs. All we know for sure is that the more you train, the more carbs you need. But counting carbs isn’t really necessary. In my research, I encountered very few elite athletes who tracked their carb intake. Instead, they just made a habit of including carb-rich foods in all of their meals and in most snacks. By doing the same, and by adjusting your overall food intake based on your activity level, you will be sure to get the right amount of carbohydrate for you.
Despite all of the research showing the benefits of a high carb intake on endurance performance, many runners today are being persuaded to switch to low-carb diets on the belief that reducing carb intake increases the muscles’ fat burning capacity and endurance. But studies have repeatedly demonstrated that the boost in fat-burning capacity resulting from a low-carb diet, particularly from a high-fat low-carb diet, actually impairs endurance performance. A 2014 study by Polish researchers found that four weeks on a high-fat low-carb diet reduced time-trial power by an average of 12 watts in a group of competitive mountain bikers.
Do results such as these mean that runners should eat lots of carbs all the time? No. New research has shown that endurance athletes can benefit from doing select workouts in a carbohydrate-deprived state. Most recently, French researchers observed that time-trial performance improved in cyclists who maintained a high-carb base diet but completed three morning rides per week, each preceded by a 12-hour carbohydrate fast and a carb-depleting interval workout. Interestingly, this benefit had nothing to do with fat burning. Rather, doing occasional carb-fasted workouts in the context of a high-carb diet appears to boost endurance performance by increasing aerobic capacity, which is the opposite of what a low-carb diet does.
Carb-fasted workouts are new enough that the most effective way of practicing them is not yet known. I believe that one to two of these sessions per week is a good starting point. The most convenient way to do them is first thing in the morning either before breakfast or after a no-carb breakfast. Carb-fasted workouts may take the form of high-intensity intervals or long, slow endurance runs.