It is difficult to know if you should be eating pre-workout. Many different sources advise consuming gels, bars or even a meal. Others maintain that to get the greatest benefit from your workout, you should exercise on an empty stomach. Whether or not to eat before working out depends primarily on what type of working out you will be doing, when you will be doing it and how long you will be exercising. In most cases, you should consume some type of snack that can be easily digested approximately one hour prior to working out.
If you are engaging in some type of endurance exercise, it is very important to eat pre-workout. Eat approximately two hours before you plan to work out. Ideally, you should eat a combination of carbohydrates and low fat protein. Try a slice of whole grain toast with almond or cashew butter. If you are going to be working out for an hour or more, you will also need some sort of electrolyte replacement drink or gel. You can consume the drink or gel halfway through your workout, or you can consume it half an hour prior to working out.
If you are doing some type of casual exercise, such as a light aerobics class or 20 minutes or less on the elliptical machine, you don't need to worry about eating a pre-workout meal. You also don't need to worry about energy drinks, gels or any of the extras. This does not mean that you should go to your workout hungry. You don't really need extra food, but because your body will be expending energy, you should not start your workout feeling deprived.
Exercising regularly takes planning. Even if you're doing a basic workout, it would be very difficult to get through it if you only ate an apple for breakfast and that was eight hours ago. If your workout doesn't require a pre-workout meal, you should make sure that you had your last meal within three hours of your workout. If you are competing in an all-day event, you need more than just a pre-workout meal; you need to be fueling your body throughout the day to maximize your performance.
The bottom line is that you need to have enough energy reserves (or glycogen) in your body to complete your workout effectively, but you do not want to have so much reserve that you begin your workout feeling full and nauseous. You also want to avoid the unnecessary calories found in many energy gels and sports drinks, unless you require sustained energy for an endurance event. Ultimately, deciding whether to eat a pre-workout meal or snack will come down to trial and error and what works best for your body.