Too many endurance athletes fuel their bodies under the premise, “If I burn 500-800 calories an hour, I must consume that much or I’ll bonk.” However, as Dr. Bill Misner says, “To suggest that fluids, sodium, and fuels-induced glycogen replenishment can happen at the same rate as it is spent during exercise is simply not true. Endurance exercise beyond 1-2 hours is a deficit spending entity, with proportionate return or replenishment always in arrears. The endurance exercise outcome is to postpone fatigue, not to replace all the fuel, fluids, and electrolytes lost during the event. It can’t be done, though many of us have tried.” In other words, your body can’t replenish calories as fast at it expends them (ditto for fluids and electrolytes). Athletes who try to replace “calories out” with an equal amount of “calories in” usually suffer digestive maladies, with the inevitable poorer-than-expected outcome, and possibly the dreaded DNF (“Did Not Finish”). Body fat and glycogen stores easily fill the gap between energy output and fuel intake, so it’s detrimental overkill to attempt calorie-for-calorie replacement.
Keep this in mind if you’re doing ultra-endurance events, especially if you’ve had to “alter the game plan” and are unable to stick to your planned hourly calorie intake. For example, let’s say you’ve been consuming an average of 280 calories an hour but the heat or other circumstances (such as climbing a very long hill) prevents you from maintaining that desired hourly average. DO NOT try to “make up lost ground” by consuming additional calories; it’s not only unnecessary, it may very well cause a lot of stomach distress, which will hurt your performance. Remember, during periods where fuel consumption may be less than your original hourly plan, body fat stores will effectively fill in the gap, thus eliminating the need to overcompensate with calories.
Recommendation: Intake of 240-280 calories per hour, on average, is sufficient for most endurance athletes. Lighter weight athletes (<120-125 pounds) may need less, while heavier athletes (> 185-190 pounds) may need slightly more. Experiment in training to determine your specific requirements, using 240-280 calories/hour as a base to work from. If you fall behind on your average calorie intake, do not consume excess calories to bring your average back up.
Next time, Mistakte #4: Inconsistent Electrolyte Supplementation