Rushing out of the house for your morning aerobics class, do you grab a piece of fruit for the ride, or just a bottle of water? Eating may fill you up, slow you down and perhaps even make you feel sick while exercising; an unfed body will use glycogen stores, which will tire you out more quickly. Sports scientists have been studying optimum eating times and what to eat for fuel, mainly to optimize performance in professional athletes. Researchers Ashley Chambers and Dr. Len Kravitz say that there is a time to eat before and after exercise, to minimize fatigue and maximize performance and endurance.
Homones and Exercise
Exercise has a striking effect on hormones. Catabolic hormones help break down nutrients; anabolic hormones build up muscle. During aerobic exercise, the anabolic hormones help convert glycogen into glucose, to help sustain energy levels. Eating certain foods at certain times before and after exercise will help keep these hormones running efficiently. Eat nothing before a workout, and low glycogen stores will make your muscles weaker. About 45 minutes after the workout, your anabolic hormones start to repair muscle and decrease inflammation. This calls for refueling. About one to three hours after your workout, your body should start getting the benefits of exercise and replenishing glycogen stores. This also calls for more food, according to research published in the "Journal of Sports Sciences."
Before and During Workout
A drink or shake containing a 4-to-1 ratio of carbohydrates and protein is ideal, Kravitz and Chambers write --- 24 grams of carbs and 6 grams of protein, for example. If you would prefer real food, they recommend eating 75 grams of high-fiber breakfast cereal and drinking 300 milliliters of water. Though it doesn't sound all that appetizing, this combination, eaten 45 minutes before a moderate-intensity workout, prolonged energy and enhanced exercise capacity. Research published in the "Journal of Applied Physiology" agreed that a meal in the moderate range on the glycemic index eaten before exercise can enhance performance. Moderate glycemic-index foods --- those your body burns neither too fast nor too slowly --- will keep you going without making you feel uncomfortably full.
What to Eat
The optimum 45-minute window to eat before exercise is not always practical. The Australian Institute of Sport suggests some alternatives. Three to four hours before exercise, eat pasta with low-fat sauce, baked potatoes with cottage cheese or a sandwich with a protein filling, plus a banana to keep you energized until your workout. If you have an hour or so before your class, try something lighter, such as a smoothie or cereal bar. A piece of fruit is also good but might not have enough calories. If you have less than an hour before your class, try a sports drink or a sports bar.
Empty Stomach
If you are exercising to burn fat, one study from the journal "Medicine and Science in Sports and Exercise" suggests that exercising on an empty stomach burns more fat. However, those who do exercise on an empty stomach run out of energy more quickly. Researchers explain that skipping breakfast is most suitable for a morning workout, because eating carbohydrates (such as breakfast cereal) slows down the fat metabolism for nearly six hours afterward. Andrew Greenberg, the director of the Obesity and Metabolism Laboratory at Tufts University, argues instead that this fasting before exercise burns fat within muscles, and will not affect overall body fat. It also could make you even eat more than usual afterward your workout. The empty-stomach method is best used occasionally, about once a week, by young, healthy and relatively fit people.
What Not to Eat
The food you eat before your workout has to have been digested and absorbed. Otherwise, energy that could be used to exercise is diverted to the stomach. Fatty foods take longer to digest and might make you feel uncomfortable during your workout. Eating large amounts of anything will take longer to digest, but might be tolerated if you are doing a low-impact aerobic activity, such as cycling. Running, jogging or high-impact aerobics will move your stomach around during exercise, resulting in gastric distress. You might keep running, but it will be for the restroom.
Water
Your biggest friend during your workout is water. Most instructors advise short water breaks to rehydrate after intense bursts of exercise. Water helps keep salt balanced and also helps the blood carry nutrients to your cells. The American College of Sports Medicine suggests two to three cups of water before a workout, and the same amount after. During the workout itself, you should aim for one cup of water every 20 minutes. These are general recommendations; if your bladder feels uncomfortably full, or your stomach feels too full, drink when you feel thirsty.
References
- Ask Dr. Len Kravitz: Nutrient Timing: The New Frontier in Fitness Performance
- "Journal of Sports Sciences"; Carbohydrates and fat for training and recovery; L.M. Burke et al.; January 2004
- Amercian College of Sports Medicine: Position Stand: Exercise and Fluid Replacement
- Australian Institute of Sport: Eating Before Exercise
- USA News Week: Workout Without Breakfast Burns More Fat : Weight Loss Study
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