An emerging concept with growing support involves providing protein with
and in some cases using less carbohydrate. While it is true that strength and power athletes are well versed on the importance of consuming protein to promote muscle growth, most endurance athletes have not considered protein important because building muscle is not a priority. Further support for this new paradigm comes from a study performed in female triathletes. They exercised for 3 hours followed by a timed test to exhaustion on a cycle ergometer on two occasions. They were provided either a standard 6% carbohydrate drink providing 24 kcal or a low carbohydrate protein supplement (3% carbs and 1.2% protein) providing 17 kcal. Drinks were provided every 20 min during exercise. When the triathletes were provided the low carb+protein drink they fatigued after 50 min compared to just over 42 minutes when they were provided the carb-based drink. This is another study that confirms a carbohydrate-protein combination is superior to carbohydrate alone, and suggests that when protein is consumed during prolonged endurance exercise less carbs are needed to fuel exercise.
McCleave EL, Ferguson-Stegall L, Ding Z, Doerner PG 3rd, Wang B, Kammer LM, Ivy JL. A low carbohydrate-protein supplement improves endurance performance in female athletes. J Strength Cond Res. 2011 Apr;25(4):879-88.