Nutrition by the numbers.

Runners are often advised to devote 60% of their diet to carbohydrates, no more than 25% to fat, and 15% for protein. Easy enough, right? It may sound simple, but when it comes down to making food choices-puffing meals on the table and snacks in your mouth-you might need a little help. How should you apply the 60-25-15 rule of thumb? There is a method, and although math-phobics may have a little difficulty, applying the Nutrition Facts printed on food labels and developing an understanding of your energy needs will give you the tools to plan your diet to meet your athletic demands.

First things first. You need to know your calorie budget-- that's the total daily number of calories you need to maintain your weight. Multiply your weight by 10 calories per pound. This is the number of calories you need for basic metabolism: breathing, pumping your blood, and maintaining the cells of your body-Resting Metabolic Rate. A 140-pound person has a Resting Metabolic Rate of 1,400 calories.

Next, add about half that again (in this example 700 calories) for normal daily activities, just going about the business of life. Adjust this up or down depending on whether you are more or less active in your daily life than the average person. For example, if you drive everywhere, have a desk job, live in a one-story house, and have a lawn service, your daily life may require less than half of your Resting Metabolic Rate. Assuming an average activity level, our 140-pound example would need 2,100 calories for the basics.

Now, add the number of calories your training requires. Runners can estimate about 100 calories per mile. So if you run an average of seven miles a day you would add 700 additional calories to fuel your workouts. This would increase the calorie budget of a 140-pound runner to about 2,800 calories per day. (If you need to lose weight decrease the total by no more than 20%.) Now you can divide your calorie requirements evenly throughout the day to determine what you should shoot for in your meals and snacks.

Your protein budget should be calculated on body weight rather than total calories. Protein is given in grams on nutrition labels and is best calculated for athletes by 0.5 grams to 0.75 grams per pound of body weight (which is 70 to 105 grams of protein per day for the 140-pound person). Your fat budget should be 25% of total calories, or 700 fat calories for a 2,800-calorie diet. Carbohydrates should fill in at 60%, or 1,680 calories per day. Finally, carbohydrates contain about 16 calories per teaspoon, proteins have roughly 16 calories per teaspoon, and fats have 36 calories per teaspoon.

Now you are armed with the information you need to apply 60-25-15 to your diet by using Nutrition Facts and some basic calorie information about unlabeled foods like apples, carrot sticks, etc. if you weigh 140 pounds and run about seven miles a day, you can divide your 2,800 calories into three 700-calorie meals and 700 calories of snacks and plan accordingly. Once you are comfortable with the basics, it is easy to apply regular eating habits that don't stray too far over time from your goals. You'll know you are using your diet to give you your best performance and great overall health. (From Nancy Clark, MS., R.D., whose book, Sports Nutrition Guidebook, is available at a 20% discount to American Running members at 1-800-776-2732)