Caloric requirements are higher. Athletes who train heavily require approximately 44-50 kcal/kg bodyweight. So for example, a 90 kg (200 lb) man who is training for several hours each day, would require 90 kg x 44-50 kcal/kg = 3960 – 4500 calories per day. Average adult requirements are typically between 1800-2200 calories per day.
Carbohydrate requirements are still within the recommended 55-60% of calories to fuel active muscles, but because caloric requirements are elevated, this translates into a much higher carbohydrate intake than a less active person. Carbohydrate requirements could be between 6-10 g/kg body weight. The 90 kg man would require 90 kg x 6-10 g/kg = 540 – 900 g carbohydrate per day. This equals approximately 20 servings from the Grain group, 8-14 servings from Fruits & Vegetables and 3-4 servings of Milk and Milk Products, plus sports drinks each day.
Protein needs are moderate, but again within the 15-20% of total calories taken in. Less active people require about 0.86 g/kg body weight of protein. Heavily training athletes require about 1.4-1.7 g/kg body weight. Our 90 kg man would require 90 kg x 1.4-1.7 g/kg = 126-153 g protein per day. A 1 oz. serving of meat provides about 7 grams of protein. A serving of meat (3-4 oz.) provides about 21-28 grams, so consuming 4-6 servings from that group plus milk and milk products, can easily help even a heavily training athlete meet their protein requirements.
Due to the high caloric requirements of heavily training individuals, there is no need to overly restrict fat intake. It is certainly not a free for all to indulge in large amounts of unhealthy fats, but you can be liberal with healthier choices such as canola and olive oil, avocados and nuts and seeds. You will require about 20-30% of your calories from fat, so for our 90 kg friend who needs roughly 4500 calories per day, that can be as much as 150 g fat per day or roughly double an inactive person. Just remember to make healthier choices when choosing the fat sources to include in your diet.
Based on guidelines specified in the Position of Dietitians of Canada, the American Dietetic Association, and the American College of Sports Medicine paper on Nutrition and Athletic Performance.