The Science of Sugar and Athletic Performance
For many, the idea of eating candy or other sweets while running may seem counterintuitive to a healthy lifestyle. However, for endurance athletes, consuming simple sugars is a strategic nutritional choice backed by sports science. The human body's primary fuel source for high-intensity exercise is carbohydrates. During prolonged running, the body relies on stored carbohydrates, known as glycogen, which are primarily stored in the muscles and liver. These glycogen stores are limited and can be depleted in as little as 90 minutes of high-intensity activity, leading to a significant drop in energy, a phenomenon known as "hitting the wall" or "bonking".
This is where simple sugars come into play. Simple sugars, found in sweets like gummies, gels, and sports drinks, are simple carbohydrates. Unlike complex carbohydrates found in whole grains, which take longer to break down, simple sugars are rapidly digested and absorbed into the bloodstream. This provides a quick and efficient infusion of energy directly to the working muscles, helping to replenish depleted glycogen stores and prevent performance-damaging fatigue.
Simple vs. Complex Carbohydrates for Runners
Runners need to understand the timing and purpose of different types of carbohydrates. While complex carbohydrates are crucial for daily energy and nutrient intake, simple carbohydrates serve a specific function during and immediately after intense exercise. Consuming fibrous complex carbs during a run can cause gastrointestinal distress, while the quick energy from simple sugars is less likely to upset a runner's stomach.
- Complex Carbohydrates (Slow Release): Found in foods like whole-grain oats, pasta, and potatoes, these provide sustained energy and are best consumed in the hours or days leading up to a long run to build up glycogen stores.
- Simple Carbohydrates (Fast Release): Found in sports gels, chews, and certain candies, these are ideal for quick energy boosts during a long run or immediately afterward to kickstart recovery.
The Strategic Timing of Sweet Intake
Successful fueling during a run isn't just about what you eat, but also when. A strategic approach helps maintain a consistent energy supply and avoids a dramatic drop in blood sugar.
- Before the run: For long or intense workouts, a small, easily digestible, simple carbohydrate snack (like fruit snacks or a sports gel) 15–20 minutes before starting can top off energy reserves. For pre-race meals consumed 1-4 hours beforehand, focus on mostly carbohydrates with moderate protein.
- During the run: For exercise lasting over an hour, runners should aim to consume 30–60 grams of carbohydrates per hour. For events over 2.5 hours, some athletes may increase intake to 90 grams per hour by using a combination of glucose and fructose sources to maximize absorption and reduce stomach discomfort.
- After the run: Simple carbohydrates, paired with protein, can accelerate post-exercise recovery by replenishing muscle glycogen stores quickly. Options like chocolate milk or protein bars with sugar are effective.
The Importance of Gut Training
Just as runners train their muscles, they must also train their gut to handle the specific fuels needed during endurance events. Consuming a high volume of carbohydrates during intense exercise is physically demanding on the digestive system, which experiences reduced blood flow as the body prioritizes sending blood to working muscles. This can lead to gastrointestinal issues like cramping or nausea. By practicing a fueling strategy during training, runners can improve their body's ability to absorb carbohydrates efficiently and with less discomfort.
Comparison of Runner's Fueling Options
| Fuel Source | Carbohydrate Type | Absorption Speed | Gastrointestinal Friendliness | Electrolytes Added? | Cost vs. Convenience |
|---|---|---|---|---|---|
| Energy Gels | Simple (glucose, fructose, maltodextrin) | Very Fast | Generally good, specifically formulated for digestion | Often included | High convenience, higher cost |
| Gummy Candies | Simple (sucrose, corn syrup) | Fast | Can be variable, some dyes may bother stomachs | Rarely included | Moderate convenience, lower cost |
| Sports Drinks | Simple (glucose, fructose) | Fast | Good, designed to be easy on the stomach | Always included | Low convenience, moderate cost |
| Dried Fruit | Simple (fructose) | Moderate-Fast | Good in moderation, high fiber can cause issues | No | Moderate convenience, moderate cost |
| Whole Grains (e.g., Oatmeal) | Complex (starches, fiber) | Slow | Poor; high fiber can cause GI distress during exercise | No | Low convenience, low cost |
Conclusion
Far from being a nutritional misstep, the practice of eating sweets while running is a cornerstone of endurance sports nutrition. The rapid absorption of simple sugars provides the immediate energy needed to sustain performance during long, intense efforts, directly replenishing muscle glycogen stores. For optimal results, runners must understand the science behind fueling—knowing when to consume simple carbs for quick boosts versus relying on complex carbs for daily energy. By strategically incorporating sweets and other high-carb options like energy gels and sports drinks into their fueling plan, runners can effectively manage their energy levels, delay fatigue, and improve their performance, making that finish line feel a little closer and a lot more attainable. Mastering this fueling strategy through practice is as crucial to success as the physical training itself.
To learn more about the science of fueling strategies for runners, read the article "Fueling strategies for distance runners" by the Mayo Clinic Health System.
