Deciding what to eat before a workout can be tricky. If the session follows a night of sleep with your body in a fasted state, it seems like common sense to eat something. If you are doing a pre-lunch workout, it may have been hours since you ate breakfast. How do you decide what to consume? Without going into depth about the pros and cons of fasted workouts or intentional carbohydrate depletion, let’s just look at some simple truths and some ideas to consider for yourself as you navigate fueling for optimal function.
First, consider that carbohydrates are necessary for skeletal muscle contraction and brain function. Glycogen is the storage form of carbohydrates, and is found mostly in the liver and the muscles. If glycogen stores are very low, an athlete may experience fatigue, fuzzy thinking, and a loss of energy. In long events, this is often referred to as bonking. It’s actually a state of hypoglycemia, when blood sugar decreases below normal levels.
You may have experienced this by simply missing a meal and having a busy day. At some point weakness sets in, and you have the realization that you need to eat. For the athlete, carbohydrates consumed three to five hours before exercise helps replenish muscle glycogen, while carbohydrate intake one to three hours before and up to a workout optimizes liver glycogen.
Fortunately, when carbohydrates are consumed during exercise within sports nutrition guidelines, any effects of pre-exercise carbohydrate intake on either metabolism or performance are negligible or at least diminished (Burke, Clinical Sports Nutrition). This means that if all else fails and you not only missed a meal but don’t have time for proper pre-fueling, consuming carbohydrates in the form of gels, sports drinks, or bars can provide the same benefit to the working body.
Some athletes experience a reactive or rebound hypoglycemia when ingesting carbohydrates in the hour before exercise, as a large rise in plasma glucose and insulin occurs and then a rapid fall with the onset of exercise. An interesting series of studies (Jentjens and Jeukendrup 2003, Moseley, Lancaset, and Jeukendrup 2003) demonstrated that “certain individuals may develop hypoglycemia when carbohydrates are ingested in the hour before exercise, although this was not a predictor of performance” (Jeukendrup, Gleeson
Science in practice
Three to five hours out: low-glycemic index carbohydrate-balanced meal
bagel sandwich with PBJ
hummus and vegetable sandwich on whole grain bread
rice and tofu
pasta with vegetables
One hour out: this will vary by individual — some are better having nothing, others may go with a low-glycemic snack
banana and peanut butter
toast with jelly
Five to 15 minutes out: opt for an easily-digestible fuel source
packaged gels, bars, sports drinks
Bail out plan: If all else fails, plan to carry a sports drink so you can consume carbohydrates during the workout. If your workout is over 90 minutes, you’ll need carbohydrate intake as well.
Remember that fueling for a workout is like putting gas in your car — at some point, you will run out. Think about what you’ve eaten in the hours before your workout, and make choices accordingly. Since each person is different, note that you’ll need to test your own fueling approach.
Your needs will vary based on the type of workout as well, so if you’re going to run 800 repeats on a track, don’t consider going without proper fueling! If you’re taking a 30-minute light spin on your bike, it’s a different story. Your fueling plan should be fluid — your goal is to maintain some sort of homeostasis, limit stress response, have positive workout gains, and stay healthy overall.