"Two of the most important aspects of an athlete's diet are the quality of the food and the timing of the meals," says Beth Wolfgram, a registered dietitian with the University of Utah who helped retool my approach to eating.

The quality is easy. Rely on things like homemade pasta sauces (tomatoes, garlic, and extra-virgin olive oil), omelets, stir-fry, bean-and-rice burritos, broiled fish, sautéed chicken, and colorful salads. But with jobs, families, and training schedules, the timing can require major adjustments. "The two most common problems that arise," says Wolfgram, "are not eating often enough and top-loading—skipping meals during the day, then gorging at night."

First rule? Sometimes you have to force yourself to eat. You might not feel hungry before a morning run, but your body needs the fuel, especially for a long workout. Otherwise, you won't be able to train hard enough to get the full benefit. Even more important is the recovery meal, which is absolutely vital if you plan on training hard again within the next 24 hours. "For every kilogram of body weight [pounds divided by 2.2], you'll want about 1.2 grams of carbs and 0.1 gram of protein," says Andrea Chernus, a New York–based dietitian and exercise physiologist. So, for a 160-pound guy, a good recovery meal should deliver about 87 grams of carbs and seven grams of protein. Three ounces of cereal with fruit and milk would do the trick. Get it all down within what nutritionists call the "golden hour"—the 60-minute period following a workout, when the body's ability to absorb nutrients peaks.