Eating before you exercise is vital to a successful workout. If you don't supply your body with sufficient energy, you'll be unable to perform physically at your maximum capacity. In most cases, however, the energy you burn during exercise comes from the meals you've eaten over the two to three days prior to working out. What you eat during the hours before you exercise will stave off hunger, keeping your blood sugar high and your mind focused throughout your workout.

Throughout the day before your workout, it's advisable to eat plenty of complex carbohydrates, according to the Iowa State University Extension. Black beans are a prime example of complex carbohydrates, as are brown rice, and whole grain breads or pastas. Carbo-loading is a practice used by some athletes before major sporting events to maximize their body's "fuel". If you decide to use black beans as part of a carbo-loading diet, Mayo Clinic recommends getting no more than 50 to 55 percent of your caloric intake from carbs during the week before the event and up to 70 percent of your calories from carbohydrates during the final four days.

While carbs are useful prior to training, you should avoid excessive fat or protein consumption, which takes longer to digest and will provide you with less energy by the time you're ready to work out. Black beans do have fairly high quantities of protein, with more than 7 g per cup, when cooked. On the other hand, black beans are extremely low in fat, with less than half a gram of fat per cup of cooked dry black beans. Canned black beans may have marginally more fat, along with much more sodium.

When you should schedule your last meal before a workout depends largely on your own body and metabolism. As a general rule, have a large meal at least three hours before your workout. Have a smaller meal up to two hours beforehand. Smaller snacks are okay up to an hour before you train. For example, a large meal with black beans might include black bean soup, rice and vegetables. For a smaller meal, you might have a large black bean burrito. Your snack could be a single taco with lettuce, tomato, a small serving of black beans.

What you eat before a workout isn't your only dietary consideration -- you should also attend to your fluid intake to ensure you'll be hydrated throughout training. If you eat black beans from a can or a pre-packaged black bean dish, check the sodium content carefully. It's common for ready-made black bean soups or even seasoned, dried black beans to contain a lot of salt, which can dehydrate you if you don't compensate with extra water. After you've finished exercising, don't hesitate to finish off any leftovers. To replace the glycogen, or blood sugar, that you've depleted during your workout, it's highly advisable to eat a combination of proteins and carbohydrates, such as black beans.