Traditionally, a high-carbohydrate diet is recommended for athletes, but the “train-low,compete-high” modality is becoming more popular. This paradigm suggests training with low carbohydrate stores (read: fasted) will teach your body to use fat more efficiently, while competing with high carbohydrates (read: carb loading) will provide a performance boost.
Our body stores enough carbohydrates for about 90-120 minutes of exercise. Although we’re usually using a mix of fat and carbohydrates for energy, carbohydrate metabolism dominates at higher intensities. When carbohydrates run out, we derive most energy from fat, which is a much slower process. Enter the bonk: this shift results in fatigue and reduced intensity. Relying more on fat early on in exercise spares our limited carbohydrates and delays this dreaded bonk.Studies have found that training with low carbohydrate stores activates genes associated with your “aerobic engine” (good!) and increases fat utilization during exercise (also good!). BUT this didn’t actually result in improved performance. Training low may also reduce your ability to sustain high-intensity exercise, impair immune function, and increase muscle damage. These may all prevent you from hitting your goal!Due to the discrepancy between the molecular and performance effects, don’t put all your eggs in one basket. Try 1 or 2 of your longer, low-intensity sessions per week without eating before/during the session. However, perform all high-intensity sessions after a low-fat, high-carbohydrate snack/meal or else you risk not being able to hit your target zone; if you can’t train at race pace, you can’t race at race pace!