A higher carbohydrate diet (with ~60% of energy intake from carbohydrates, or around 5–8 grams of carbohydrate per kilogram of body mass per day) can help to increase overall endurance and attenuate fatigue from higher-volume training.[1][2] When volume is high, carbohydrate mouth rinses may benefit muscular endurance as well.[3]
Protein-wise, an intake of 1.4–2.0 g/kg of bodyweight per day is useful for building and maintaining muscle mass. Higher protein intakes (2.3–3.1 g/kg of fat-free mass per day) may help to retain muscle mass in those pursuing fat loss. In addition, recovery will likely be improved by spreading protein intake throughout the day (every 3–4 hours or so).[2]