Accounting for intensity of exercise also greatly influences daily energy intake. Obviously, an individual who walks for 60 minutes will expend considerably less energy than if he/she were to undergo a more intense activity, such as jogging, for the same duration. But even among athletes who train consistently for a given sport, energy consumption can vary drastically on a daily basis. For example, a triathlete undergoing a particularly difficult training session may expend as much as 2000 kcal in a workout, whereas in a session of lesser intensity expends only 1000 kcal.

As an approximate guide. In turn, daily energy expenditure can then be calculated by using determinations of resting metabolic rate. As an example, a 25-year-old, 70-kg (154-lb.) male would possess a resting energy expenditure of 1750 kcal/day [(15.3 X 70 kg) + 679]. Adding 20% to the REE to account for the thermic effect of physical activity brings the total to 2100 kcal. Accounting for the thermic effect of food consumption adds an additional 90 kcal (5% of REE). Finally, if he engages in running at a pace of 8 min/mile for 30 minutes, he would expend approximately 437 kcal (70 kg X .208 X 30 min). Therefore, the sum total for daily energy expenditure for this individual is approximately 2627 kcal/day

Of course, vigorous daily activities (i.e., strenuous labor) could potentially increase the daily energy expenditure. Also, lean body mass was not counted in the preceding calculation, which can radically alter expenditure calculations. Perhaps a more accurate method of estimating energy expenditure would involve determining macronutrient requirements and ratios that are based on resting metabolism, activity level, and lean body mass. Such methods will be addressed in subsequent sections, and will use protein, carbohydrate, and fat requirements of various athletic pursuits. Regardless of the calculations made, however, an appropriate dietary strategy is one that balances energy intake and expenditure, which will ultimately maintain body weight and composition.

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