- Sugary foods (e.g., donuts, candy bar, soda, etc.)--these high-glycemic foods will inevitably cause an "energy crash" during your workout. Better to eat these kinds of foods after your workout if at all.
- Fast food--these foods tend to be high in fat which can take up to four hours for your body to digest, making you feel nauseous because the fatty food will sit in your stomach while you workout
- No food at all--this will certainly make you feel lethargic and weak since glycogen (the energy fuel for your muscles) will be in short supply
- Energy drink--this is not a wise choice since the amount of sugar within the drink will cause an "energy crash" during your workout. Better to drink this after your workout if at all.
So what should you eat before your workouts? Go for the low-glycemic foods which won't cause an energy dip during your workout and are relatively easy to digest. Try a piece of fruit (e.g., apple, orange, banana, grapefruit, etc.), a whey protein shake, black beans, brown rice, quinoa, raisins, oatmeal, sweet potato, whole-wheat bread, whole-wheat tortilla or whole-wheat pasta. You should eat these kinds of foods within an hour of your workout. Keep in mind that the most readily available macronutrient within your body will be used for energy during your workout. This means that the macronutrient content of your most recent meal before your workout will affect what substrates are used during exercise. For example, if you ate mostly carbs before your workout, than more carbs will be burned as fuel for energy during your workout. This is important because if you're someone who wants to lose bodyfat it would be better to avoid consuming a pre-workout drink containing simple carbs. The reason for this is because the simple carbs would be preferentially used by your body for energy rather than your stored bodyfat.
BOTTOM LINE: If you're trying to lose bodyfat, the worst thing for you to do is to drink an energy drink before your workout. The sugar in the drink will be used for energy rather than any stored fat from your body. Instead, drink plenty of water before, during and after your workout. If you're trying to gain muscle mass, then it is okay to consume an energy drink before your workout for the quick energy source but be sure to eat a low-glycemic food beforehand to avoid "crashing" during your workout.
Brian Danley, CFT
"Motivation is what gets you started. Habit is what keeps you going."