There is an obvious need for sufficient calories during intenstive training. Not so obvious are the specific macronutrient and micronutrient needs of the body and the fact that many nutrients are not easily stored by the body, forcing us to consume healthy food regularly (several times per day, as opposed to just one large meal per day). The more balanced an athletes meals, and the more evenly they are spaced throughout the day, the fewer the calories that an athlete needs to eat. There is of course a lower limit to this, but typically an athlete that is not eating healthy balanced meals evenly spaced in their day must eat 25% or more calories compared to an athlete that is eating balanced meals and pacing their calories. Balance comes down to unsaturated fats, moderate (10-25% of total calories) protein, whole grain starches and fruits/vegetables. Caloric pacing comes down to not eating more than 600 Cal at any given time and not going more than a few hours without eating at least a small healthy snack. Athletes will have an appetite that exceeds their caloric needs; for this reason if an athlete does not eat a significant amount of vegetables in each lunch and dinner they are likely to overeat and actually gain body fat during the training season. I know many athletes personally who have experienced this problem: Gaining body fat whenever they start training harder. The last piece of the equation is drinking 1 Liter of water for every 1000 Cal in the diet PLUS replacing one\'s perspiration losses during training. You estimate your perspiration losses by weighing yourself before and after exercise and adding this to the weight of the fluids you drank during exercise between the weigh ins (1 Liter i.e. 32 oz of fluid weighs about 2 lb). There are 250 mg of sodium (1/4 teaspoon of table salt) in each Liter of perspiration. That thumbrule will help you determine whether or not you should consider adding salt to your diet. If you eat out or add salt to your meals you likely to not need to intentionally increase your salt intake, but if you don\'t then it might be necessary in order to regain your hydration status. Excess salt is bad for health, but so is a severe shortage of salt from high levels of training. What, When and Water. All three must come together to provide the basis for your training. There are detailed equations available from a variety of sources to determine caloric needs during specific types of training, but they only give you a ballpark estimate since they do not take into account differences in athlete\'s physiology or the details of how they eat (what, when and water). There is no cookie-cutter answer to a rigorous sports nutrition program. Instead you have to look at your over-all nutrition pattern. I have several detailed handouts to help athletes navigate this process, which can be found on my website on the \"downloads\" page www.DrClydeWilson.com