The Army Times suggests eating food or supplements that have protein before a workout to boost energy. They stress the importance, however, of eating lightly prior to doing any type of crunches in order to avoid getting stomach cramps or gas during the exercise.
The Army Times offers guidelines for keeping the body fueled and well-prepped for physical training sessions. In recommending preparation routines for physical training tests, they advocate avoiding foods loaded with sugar before a workout. Sugar may attract some people because it offers a quick pick-me-up, but it has a tendency to sap energy after a short time.