Diet significantly affects athletic performance, and adoption of a dietary strategy that meets an athlete’s nutrition goals will maximize the possibility of competitive success. Over the years, the focus has shifted from a high intake of (animal) protein to the role of carbohydrate and water. Today, there is a growing recognition that the primary role of sports nutrition may be to promote the adaptations taking place in muscle and other tissues in response to the training stimulus. There is also much interest in the implications of manipulation of the fat and carbohydrate content of the diet. This publication contains the proceedings of the 69th Nestlé Nutrition Institute Workshop held in Hawaii in October 2010. The aim of the workshop was to explore the effects of nutritional manipulations on the metabolic responses to acute and chronic exercise. Another goal was to further identify the possible role of these dietary interventions in promoting adaptive changes in muscle, adipose tissues and other potential sites of limitation to exercise performance. Papers cover the three macronutrients carbohydrate, fat and protein, plus an additional chapter on water, together with the accompanying discussions.