This is an excerpt from Gold Medal Nutrition-5th Edition by Glenn Cardwell.
What to Eat and Drink Before, During and After Exercise
"I came out with high energy, which I have been lacking in the last couple of games. I think it was the baked beans on toast for pregame."
Basketballer Lauren Jackson during the women's world basketball championships (2002)
Dietary advice to athletes has changed over the years. In the beginning it was purely speculation and experimentation, before science gave us a better understanding. We now know that what you eat, and when you eat it, will make a big difference to how you perform. It can be a bit tricky for some people to work out what and when to eat on the big day. This chapter will help you to be your best at event time.
Nutrition Before the Event
Before exercise, a meal or snack should provide sufficient fluid to maintain hydration, be relatively low in fat and fiber to facilitate gastric emptying and minimize gastro-intestinal distress, be relatively high in carbohydrate to maximize maintenance of blood glucose, be moderate in protein, be composed of familiar foods, and be well tolerated by the athlete.
Position of the American Dietetic Association, Dietitians of Canada and the American College of Sports Medicine: Nutrition and Athletic Performance (2009, 510)
Some people eat far too close to an event or training session and find themselves feeling quite unwell soon after the start of exercise. Others can leave too long between a meal and the start of their sport. I met a footballer who wouldn't eat after his 8:00 a.m. game-day breakfast because he thought he might vomit during the game. His problem was that he was hungry and tired by game time. ‘Any ideas?' he asked. Well, because the game didn't start until 3:00 p.m., I introduced him to the concept of lunch. He thought that the stomach took over a day to empty.
The following sections address key issues regarding eating before exercise.
High Carbohydrate and Low Fat
The preexercise meal needs to be high in carbohydrate to top up your glycogen stores for endurance. The glycemic index (GI) of the foods will probably have little bearing on your performance unless that performance is longer than 120 minutes, but you might want to experiment with low GI foods. For example, a light meal of 75 to 150 grams of carbohydrate will suit most people (about 1 to 2 g per kg of body weight) as a preexercise meal. The same amount of carbohydrate will be needed after exercise to start the process of replenishing muscle glycogen stores. After a moderate amount of exercise (e.g., a 60- to 90-minute workout), you will need 5 to 7 grams of carbohydrate per kilogram of body weight in the following 24 hours, which is 350 to 490 grams for a 70-kilogram (154 lb) person (probably less for females or if the exercise is low intensity).
The preexercise meal should also be low in fat so that it empties as quickly as possible from the stomach and into the small intestine where it will be digested and absorbed into the blood. Food remaining in the stomach when you begin your activity is likely to make you feel uncomfortable, especially in running-based sports because the food can joggle up and down inside the stomach. Remember, only absorbed food can fuel the body.
Some people will tell you that you should eat plenty of protein before a workout or a hard training session. Unfortunately, there is no evidence that this is helpful. Of course, there is a very good chance that your preexercise meal will contain a reasonable amount of protein anyway because it is likely to include milk, cheese, cereal, bread, pasta, rice, meat or fish.
You may prefer a food bar as part of your pre-event meal, and most of these contain some protein. As long as you are eating enough protein over the day, your body and muscles will be happy.
Timing of Meals and Snacks
Two to three hours is usually enough time for the stomach to empty before the event. Most low-fat, light meals empty from the stomach within two hours. Almost all meals are out of the stomach within three to four hours. How close you eat to an event is up to you, but consider the following:
- You generally need to allow more time for digestion in running-based sports, such as football, netball and hockey, because any food remaining in the stomach will bounce around and make you feel uncomfortable. The food may also rise through the sphincter at the top of the stomach and burn the lining of the throat (heartburn).
- You can eat closer to the event in sports in which your body weight is supported, such as swimming, rowing and cycling. Put another way, weight-supported sports may be performed with a small amount of food in the stomach and not upset the athlete.
- Any sport that involves physical contact to the stomach such as boxing, rugby or wrestling requires an empty stomach to avoid embarrassing moments.
- Allow more than three hours between meals and sport if you get nervous. Anxiety slows the rate at which the stomach empties. This is usually an important consideration before important sport events.
- Liquid meals, such as fruit smoothies and low-fat flavoured milk, tend to empty more quickly from the stomach than solid foods do. This is a very efficient way to get food into your body if you don't want solid foods or you get nervous before events.
- Sometimes it isn't convenient to eat a couple of hours before exercise, such as when you have an early morning training session. In that case, ensure that your meal and snacks before you go to bed are high in carbohydrate. Consider diluted fruit juice or a sports drink on waking before a long early morning training session. These will top up your glycogen stores before you start.
Sugar Before Sport
Many claim that eating sugar, or a sugar-containing food, before sport can ruin your performance. The premise is that the sugar causes high blood glucose levels, which causes high levels of insulin to be released into the blood, resulting in low blood glucose levels and poor performance. This assumption is based on one study published in 1979. Although this study showed a reduction in performance after eating carbohydrate in the hour before sport, most subsequent studies have shown either a neutral effect or a performance boost of 7 to 20 per cent. It's interesting that these haven't received as much publicity as the study over three decades ago. (You will recall that a sharp rise in blood glucose levels probably doesn't occur, because sugar, or sucrose, has a moderate glycemic index.) A glass of soft drink (240 mL [8 oz] ), for example, has a moderate glycemic load of 14, so it probably won't cause a high blood glucose level.
So, don't take the old truism as natural law. Experiment with foods and fluids and find out what feels best for you. If you believe sugar is a ‘downer', then avoid it; if you think it's your ‘upper', then please enjoy a small sugar boost. It's your body.
Conveniently packaged, and popular with runners and triathletes, is the carbohydrate gel (e.g., Carboshotz, Roctane, High5 EnergyGel). Most sachets are around 30 to 45 grams (1-1.6 oz) providing 20 to 30 grams of glucose in the form of maltodextrin (medium chains of glucose molecules). Many athletes slip these inside their shorts or bike tops and retrieve them when required. Because they are a concentrated source of carbohydrate (50 to 70 per cent carbohydrate in most cases), I strongly suggest that you experiment with them during training. Although they can be consumed on their own, it makes physiological sense to dilute them by washing them down with water (around 400 to 500 mL [13.5 to 17 oz] for every 30 grams of carbohydrate). The dilution will encourage the glucose gel to leave the stomach and enter the intestine more quickly than if it were eaten alone. As a guide, have one sachet in the 10 minutes before the start of an event, and then one or two sachets per hour of sport depending on intensity. Carbohydrate gels are of most benefit to endurance athletes. For the nutrient profile of some gels, see table 8.2.
Learn more about Gold Medal Nutrition, Fifth Edition.