An athlete's dietary needs are based on training volume (weekly hours), type of physical activity, body composition, body composition goals, environmental conditions, and individual therapeutic dietary and health considerations.  Sorry folks, it's not that simple for every athlete to follow the same way of eating; furthermore, how do you defi­ne the word athlete in the ­first place-even that term is all over the map.

I would define an athlete as someone with an above-average level of fitness that may be training to be fit or to compete. We could classify athletes as recreational (physically fit but not competitive), competitive (whereby competitions are secondary to the other elements of their life), and high performance (in which case athletic competitions are the number-one personal goal and training is more or less a full-time job).

Aside from variations in competition focus for athletes, the primary difference to consider when planning the nutritional demands of athletes would be their weekly training hours, training intensity, and body composition goals. We can periodize their nutritional requirements in the same way a physical training program is periodized (i.e., specific weeks spent building endurance, strength, speed, power, or technical skills, etc.). Let's use weekly training hours as a way to illustrate sport nutrition planning.

First, let's categorize exercise weekly volume in hours to help determine dietary energy requirements. These weekly training hours would be one of the following: less than six hours, six to twelve hours, and more than twelve hours. For example, a client of mine, Ross Manning, is in his triathlon "off season" and is training fewer than twelve hours a week. In comparison, four-time Olympian Haley Wickenheiser (hockey 1998, 2002, 2006, softball 2000), and first-time Paranordic Olympian Mark Arendz (2010), easily exceed twelve weekly hours with competitions and training. In addition, Manning, the triathlete, has a personal goal to reduce body fat and fully recover from a herniated vertebral disk, while both Wickenheiser and Arendz want to maintain the lean body mass they have built up for the 2009-2010 season, as they prepare for their main events in Vancouver. Arendz doesn't have any therapeutic dietary considerations; however, Wickenheiser tends to limit some foods, specifically milk, bread, and cheese, that don't make her feel well when consumed in large quantities.

You might think that a competitive or high-performance athlete can eat whatever they want because they are expending so many calories? However, a highly tuned athlete is easily able to sense the negative physiological effects from consuming beer and wings in their post-exercise nutrition. In fact, food quality counts for all of us, but especially for high-performance athletes. A few consecutive days of unhealthy fast foods will leave an athlete feeling energy depleted, recovering poorly, and subsequently at risk of contracting the latest illness. Wickenheiser says, "My diet has always been pretty balanced. As a high-performance athlete, I am watching the timing of when I am eating as well as what I am eating. Adding some supplements as well as making sure I get enough protein and good recovery meals are probably a bigger focus with the schedule that we have right now."

As a result of greater training volume, athletes will have a higher percentage of lean body mass (LBM) relative to recreational enthusiasts; therefore, high-performance athletes will have a higher BMR (i.e., metabolism).

To support an athlete's greater metabolic rate and therefore energy requirements, athletes need additional calories from all sources: protein, carbohydrates, and healthy fats. However, the precise requirement of each of these energy macronutrients is determined in conjunction with their nutritional periodized plan and their personal body composition goals. Every athlete should have their sport nutrition plan individualized based on these important factors.

Nonetheless, a universal dietary difference for an athlete's diet, compared to a sedentary individual, would be their fluid needs. Aside from daily hydration needs to support bodily functions (generally two to three litres) it has been estimated that athletes lose anywhere from 300 to 2,400 millilitres of fluid (mainly sweat) during every hour of physical activity, depending on their exercise intensity, environmental conditions, and individual variability. The only precise way to measure personal fluid loss from physical training would be to check bodyweight immediately before and immediately after activity. Every pound lost (0.5 kilograms) reflects 500 milliliters of fluid lost (as sweat, elimination, and breathing). A reasonable guide to estimate fluid requirements during exercise would be to start with consuming ten to fifteen millilitres of fluid for every kilogram of bodyweight for every hour of activity. For example, if you weigh 155 pounds (70.3 kilograms), you may need 700 to 1,055 millilitres for each hour of training. From this starting point you can check your pre- and post-exercise weight. As well, listen to your body for signs of sufficient hydration to see whether you are on track with preventing performance-limiting dehydration. Sodium loss in sweat is also highly variable from athlete to athlete. A salty sweater is more likely to experience muscle cramping and feel symptoms of nausea during lengthy training bouts or competition. And drinking plain water will make their symptoms worse, not better, since they are further diluting their low sodium levels.

Aside from food quality-plus greater energy and fluid requirements-one of the most important dietary practices essential for athletes is to consume ample recovery nutrition as soon as possible after exhaustive training. When we deplete our energy (muscle glycogen reserves) as a result of ninety or more minutes of hard work that consuming optimal quantities of foods and fluid within the critical two-hour recovery window is essential, especially when you plan to be physically active within the next twenty-four hours. Both Wickenheiser and Arendz admit that recovery nutrition is their number-one dietary goal. Arendz, a full-time, Olympic-bound athlete and engineering student, has indicated that immediately after training he uses specific "recovery drinks and snack foods to begin the recovery process as soon as possible." Even Wickenheiser suggests that "on a regular basis for me, it's about hydrating, eating balanced high nutrient foods, and definitely making sure I am getting great food into my body post-workouts and games for recovery."

About the Author
Kelly Anne Erdman, M.S., R.D., 1992 Cycling Olympian, member of the Canadian Cycling Team, 1985-1992, is a consulting dietitian for the Canadian Sport Centre Calgary, with a practice at the University of Calgary Sport Medicine Centre.