The role of dietary macronutrients in optimizing endurance performance.

We have evaluated the evidence underlying certain key nutritional recommendations for endurance sporting activities. A relatively high daily carbohydrate (CHO) intake (> 6 g/kg/d) and CHO ingestion (30-60 g/h) during exercise appears to delay the onset of fatigue. However, the mechanisms of this effect are governed in part by an attenuation of effort perception, rather than solely as a consequence of delaying an impending energy crisis. CHO loading and ingestion also impart some neuroprotection from fatigue during prolonged exercise, as well as high-intensity, intermittent exercise. In addition, the individual response to short-term (5- to 6-day) ingestion of a high-fat diet (> 60% of calories from fat) followed by 1-day CHO loading seems to vary widely, and is most likely to be of benefit only during ultra-endurance activities. Furthermore, CHO and protein intake in the postexercise period aid in protein synthesis and restoration of muscle glycogen stores. However, athletes and their advisors must be prepared to try various nutritional strategies in order to optimize both performance and training.