Fitness Fuel

By Shannon Burgert

Dried apricots or raisins, yogurt or a bagel—which snacks will help you get the most out of your workout? The answer: They all will, but it depends on when you eat them. Certain foods are better before a workout, others afterward. What you eat and drink before, during and after exercise affects not only the quality of your workout, but also your ability to bounce back and exercise again the next day. In fact, serious triathletes call nutrition “the fourth discipline,” and they believe it’s just as important as the training for swimming, cycling, and running.

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When it comes to fueling for workouts, a healthy diet comes first, says Colleen Cooke, a sports dietician at the Boulder Center for Sports Medicine. The only difference with exercise is timing—when to eat what. A general guideline is to eat foods low on the glycemic index before exercise, and foods high on the glycemic index afterward. The glycemic index measures the effect a food has on your blood sugar level. Low-glycemic foods—such as apples, nuts and dried apricots—release sugar into your bloodstream slowly; foods high on the glycemic index—like bagels, potatoes and raisins—produce a rapid rise in blood sugar levels. After replenishing your glucose levels with high-glycemic foods, taper back to those low on the index.

During digestion, carbohydrates are converted to glucose; most glucose not immediately used as a fuel source is transported to liver and muscle tissues and transformed into glycogen for storage. (Glycogen is a highly branched glucose polymer resembling the starch in plants.) As you exercise, the glycogen stored in your muscle cells is reconverted to glucose to manufacture adenosine triphosphate (ATP), the energy source for cells.

If you exercise in the morning, Cooke recommends that you top off your glycogen stores 30 to 60 minutes before heading out with at least 50-100 calories high in carbohydrates. She recognizes that some people are not able to exercise after eating, but for those who can do so, topping off those calories is best. Cooke explains that we can carry up to about 2,200 calories in our muscles and liver at a time; by morning, we’ve typically gone up to 12 hours without fuel. Glycogen stores are depleted in about a day unless they are replenished with food.

If you exercise later in the day, eating beforehand is more a matter of preference. “Some people get light-headed if they don’t eat before a workout, especially if they’re weight-training,” says Alison Westfahl, director of personal training at Flatiron Athletic Club. “Other people do well on an empty stomach.”

If you’re exercising for more than an hour, Cooke suggests adding in some high-carb snacks, like energy bars, dried fruit, or a peanut butter sandwich, to maintain blood glucose levels. If you’re counting grams, she offers a guideline of 30 to 60 grams per hour for moderate to intense exercise. Carbohydrates (and sometimes proteins) are included in some sports drinks.

Special Tips for Cold Weather

Cold-weather training burns more calories than training during warm weather. Muscle glycogen is used up at a slightly higher rate, and shivering burns energy too. Make sure to eat well before winter training sessions—digestion produces heat. If it’s particularly cold, keep cut-up energy bars or gel packs close to your body to keep them from freezing. (Gel packs, for those unfamiliar with the term, are not those blue things you keep in the freezer for sprains, but high-carb, pudding-like energy sources.)

Toni Geer is the mother of 13-year-old Wesley, a member of the Boulder Junior Nordic Ski Team. “Nutrition is a big focus for the team,” says Geer, noting that the skiers are out for two to three hours at a time. In addition to her water bottle, Wesley carries gel packs and energy bars, and parents provide sandwiches. The night before a race, Wesley eats a big, healthy dinner packed with carbohydrates. “It’s important that you don’t get too hungry, because then you don’t perform as well,” she says.

Immediately after you exercise, rehydrate and eat something high on the glycemic index. Cooke explains that if you don’t refuel within the 30-minute window following exercise, you don’t recover as quickly. She adds, “There is some good research indicating that a ratio of three to five grams of carbohydrate to one gram of protein helps restore glycogen levels more efficiently.”

Within two hours of exercise, Cooke recommends consuming a nutritionally “solid” meal: a lean source of protein, whole grains, vegetables and fruits. Limit processed and refined foods as much as possible. As for supplements, Cooke recommends a basic multivitamin tailored for males or females; look for the USP (United States Pharmacopeia) Verified Ingredient mark. For most women, she encourages a calcium supplement.

“When you eat well during and following exercise, your body is much better prepared for the next day,” Cooke says. “It’s all about fueling so you can get good-quality workouts.”

Hydrate, Hydrate, Hydrate

The most essential nutrient, water, is often overlooked in the winter, when it’s not so appealing to drink. Cooke points out that on top of Colorado’s dry climate, fabrics that wick away moisture make it hard to realize how much fluid is lost through sweat. And don’t forget about fluid lost through respiration. “When you’re seeing your breath, you’re seeing water molecules,” she says.

If you’re headed for the snow, take a water bottle or hydration pack. If you’re downhill skiing, make sure to take some breaks to go into the lodge and drink water.

Tasha Stille, a member of the University of Colorado Snowboard Team, wears an insulated 100-ounce hydration pack on the slopes. “I go through the entire thing in a day,” she says, adding that she keeps a sports drink at the bottom of the mountain to replace electrolytes. Electrolyte replacement is important if you’re exercising for more than 90 minutes, because, as Cooke explains, “when you’re sweating, you’re sweating out salt.”

So how much should you drink? Westfahl recommends to her clients that they take in half their body weight in ounces of water as a base amount each day. When they exercise, she recommends more. “If you run for more than 45 or 50 minutes, take water with you on a fuel belt or plan your run along a path with water fountains,” she says. Cooke recommends that athletes take in four to eight ounces of water or sports drink during every 15 minutes of exercise. In the winter, she notes that warm, caffeine-free liquids can hydrate and warm the body at the same time. “If you pay attention to nutrition and hydration, you just get to play longer,” Cooke says. l


Shannon Burgert is a teacher, freelance writer and triathlete. She had half a pint of ice cream and a glass of wine while writing this article—but made sure to eat some carrot sticks first.