What to eat before you exercise
Contrary to popular belief, pre-exercise food does NOT simply sit in the stomach and hinder athletic performance. Rather, it enhances stamina and endurance. The following study confirms this point:
On two occasions, athletes exercised moderately hard until they were exhausted. In one trial, they ate a 400-calorie breakfast three hours before exercising. In the second trial, they simply had a dinner the night before. When they exercised "on empty," they biked for only 109 minutes, as compared to 136 minutes with the breakfast. That's almost half an hour longer! Exercising without fuel left them lagging. (Med Sci Sports Exerc 31(3):464, 1999)
Even if you eat five minutes before exercise, you'll digest the snack and burn it during exercise, assuming you will be exercising at a pace you can maintain for more than 30 minutes. This means, you can enjoy a granola bar and banana on the way to the gym to fuel your workout. Research suggests this pre-exercise snack can help you perform 10 percent harder in the last 10 minutes of a one-hour workout. Go for it!
Your goal is to target 0.5 grams carbohydrate per pound of body weight within the hour before you exercise. This means, if you weigh 150 pounds, you should target about 300 calories. This is far more than most athletes consume.
Obviously, the amount will depend on your stomach's tolerance to pre-exercise fuel. If you have a finicky stomach, liquids or semi-solids (Boost, yogurt, applesauce, pudding) might empty from the stomach quicker than oatmeal, bagels, bananas, animal crackers or graham crackers. The trick is to teach your intestinal track to tolerate the pre-exercise food so you can enjoy higher energy but avoid undesired pit stops.
Eating during exercise
If you are exercising longer than an hour, plan to consume carbs and fluids during exercise to maintain energy and prevent dehydration and needless fatigue. Depending on your body size, intensity of exercise and intestinal tolerance, you'll want to target about 100 to 250 calories of carbohydrates per hour after the first hour of a two- or three-hour event.
If necessary, set your watch to beep every 15 to 20 minutes as a reminder to consume eight ounces of a sports drink, a Tootsie Roll or part of an energy bar and water. If you are doing an Ironman or ultra-distance event, you'll need to consume even more (400 to 500 calories/hour).
During a moderate to hard endurance workout, carbohydrates in muscle glycogen and blood glucose supply about half of the energy. As you deplete muscle glycogen, you increasingly rely on glucose (sugar) in your blood for energy. By consuming sports drinks, gels, bananas, hard candies, peppermint patties and other carb-based foods during exercise, you will fuel your muscles, maintain normal blood sugar and prevent the dreaded bonk.
Your brain relies on the glucose in your blood for energy; keeping your brain fed helps you think clearly, concentrate well, remain focused -- and perform better. Do NOT "hold off" until after your workout to eat. Rather, fuel during workouts. For example, cyclists should eat while on the bike. Coaches should give teams a snack break during long (over two hours) practices.
Your body doesn't care if you ingest solid or liquid carbohydrates -- both are equally effective forms of fuel. You just have to learn which sports snacks settle best for your body -- gels, gummy bears, dried figs, sugar wafers, tea with honey, sports drinks, or perhaps defizzed cola. If you get your energy from concentrated calories, as opposed to sports drinks, be sure to drink additional fluids. That is, athletes who eat energy bars (or gels) during exercise can too easily under-hydrate.
Despite popular belief, sugar (as in sports drinks, jelly beans, licorice) can be a positive snack during exercise and is unlikely to cause you to "crash" (experience hypoglycemia). That's because sugar taken during exercise results in only small increases in both insulin and blood glucose. Yet, if you consume too much sugar (>250 calories/hour), the high dose might slow the rate at which fluids leave your stomach, causing sloshing, discomfort. (If you experience GI distress, slow down and work at an easier pace.)
If you will not be exercising again for a day or two, you need not worry about rapid refueling. But if you work out hard twice a day, you should consume post-exercise carbohydrates as soon as tolerable -- ideally 0.5 grams carbohydrate per pound body weight every hour, for four to five hours (300 calories per hour, if you weigh 150 pounds). Consuming some protein along with the carbs stimulates faster glycogen replacement and optimizes muscular repair and growth.
Some commercial recovery foods tout the benefits of whey protein. Current research indicates no advantage of whey over casein in terms of muscle growth. (Tipton, Med Sci Sports 36(12)2073, 2004) Yes, you can buy commercial recovery foods that contain protein, but you can just as effectively enjoy cereal with milk, a bagel with peanut butter or pasta with meat sauce. These foods offer carbs with an accompaniment of protein (a ratio of 40 gm carb, 10 gm pro).
If you prefer liquids for recovery foods, choose Instant Breakfast, chocolate milk, Boost, yogurt or fruit smoothies; they are tasty sources of carbs, fluids and a little protein. The trick is to plan ahead and have the right foods and fluids readily available.
Preventing dehydration during exercise is preferable to treating dehydration post-exercise. But if you failed to drink adequately (as indicated by scanty, dark urine), you may need 24 to 48 hours to totally replace this loss. Fruit juices, smoothies and watery fruits are better than plain water because they offer carbs, protein, vitamins and other nutrients that optimize recovery and invest in good health.
If beer is your preference, be sure to first quench your thirst with orange juice, soft drinks or sports drinks and eat some carbs (pretzels, thick-crust pizza) so you get carbo-loaded, not just "loaded!" Or think again. Would you be wiser to simply enjoy the natural high of exercise?
Copyright Nancy Clark, M.S., R.D., Feb. 2005
Sports Nutritionist Nancy Clark, M.S., R.D., counsels casual and competitive athletes at her private practice in Healthworks, the premier fitness center in Chestnut Hill, MA (617-383-6100). Her Sports Nutrition Guidebook ($23) and Food Guide for Marathoners ($20) offer abundant fueling tips. To order: send check to PO Box 650124, W. Newton MA 02465, or go to www.nancyclarkrd.com.