Pre-Workout: Enjoy Enough Calories
When you put your body through an intense workout, you need to properly fuel up with sufficient calories. If you're trying to lose weight, 1,200 calories a day is the bare mininum, but very active folks concerned about hitting a wall will have to eat much more than that.
Once you determine the right number of calories to support your needs, make sure to hit it daily to keep your body fueled and energized. Regularly underconsuming calories can deplete your glycogen stores, and make you more likely to bonk during a workout.