High-protein, Low-carb Runner's Diet

If you are looking to improve your speed, add distance or even just maintain your current level of running performance, a high-protein, low-carbohydrate diet is unlikely to help you reach your goals. In fact, such a diet will be a detriment. The top elite distance runners typically have a higher-than-average carbohydrate intake as opposed to a high-protein, low-carbohydrate intake.

Glycogen Depletion

Focus on a high-protein, low carbohydrate diet and you are likely to run out of energy about halfway through your runs, notes Madelyn H. Fernstrom, author of "The Runners Diet." That's because this type of diet leads to glycogen depletion, which limits your capacity to run. Carbohydrates are stored in your muscles as glycogen. This glycogen is used for energy during exercise. Your ability to sustain prolonged bouts of exercise, such as running, directly correlates to the levels of muscle glycogen you have.

Dehydration

A high-protein, low carbohydrate diet presents a second problem for runners. The rapid weight loss produced by such a diet often consists largely of water. This increases your risk for dehydration, which in turn degrades both mental and physical performance. Even mild dehydration affects your running ability. Dehydration also impairs your body's ability to regulate its temperature. In extremely severe cases of dehydration, this condition can lead to permanent brain damage, seizures or death.

Other Side Effects

If you decide to follow a low-carbohydrate diet while undergoing a training regimen, you may experience some unpleasant side effects. You may have mood alterations such as depression, tension and anger. You also may experience decreased immune system function, slow muscle recovery, more frequent injuries including stress fractures, kidney stones and joint pain.

Expert Insight

Energy needs for endurance athletes like runners are high. A diet that includes adequate carbohydrates will prevent early fatigue and reduce your risk for injury, notes the American Dietetic Association. Your carbohydrate and protein needs vary depending on how hard you are training. If you are performing light to moderate training, you need 2.3 g to 3.2 g of carbs per lb. body weight. If you are undertaking heavy training you need 3.2 to 4.5 g. per lb. body weight. For extreme training or high-intensity races lasting more than five hours you need 4.5 to 5.5 g. per lb. body weight.

As for protein, you need .55 to .8 g. per lb. body weight for light to moderate training or .7 to .9 g per lb. body weight for heavy training. Highly successful Ethiopian distance runners on average take in 4.4 g. carbohydrate per lb. body weight and .82 g. protein per lb. body weight. In the runners' case, this translates to about 64 percent of calories from carbs, 13 percent from protein and 23 percent from fat, notes a 2011 study published in the "Journal of the International Society of Sports Nutrition."

Carbs vs. Fat

High-protein diets are frequently also high in fat, the second source your body turns to for energy. If you are hoping to boost performance, fat is not your best energy source. Carbohydrates are released much more quickly than fat for energy within your muscles -- about three times as fast. Carbohydrates also yield more energy per unit of oxygen utilized in your body than fats. Since oxygen often is a major limiting factor in during running events, using the energy source that requires the least amount of oxygen per calorie produced makes sense.