The Science Behind Sugar and Running
For athletes, carbohydrates are the body's primary fuel source, and sugar is a simple, fast-acting form of carbohydrates. When you consume sugar, it is quickly digested and absorbed into the bloodstream as glucose, which is then transported to your muscles for immediate energy. This rapid availability makes simple sugars, like those found in energy gels or certain sweets, effective for providing a quick boost, especially during intense or long-duration exercise.
However, the key is proper timing. Ingesting too much sugar, or the wrong kind, at the wrong time can trigger a rapid insulin spike, followed by a sudden drop in blood sugar levels, a phenomenon known as reactive or rebound hypoglycemia. This can cause symptoms like weakness, dizziness, and fatigue, severely impacting your performance. For this reason, runners must be strategic about when and what kind of sweet they consume.
Strategic Timing for Different Runs
The optimal time to eat a sweet before running depends largely on the duration and intensity of your workout. Your fueling strategy should be different for a short, easy jog versus a long, intense training session.
For Short Runs (under 60 minutes)
For runs lasting less than an hour, especially at a lower intensity, most people have enough glycogen stored in their muscles to complete the workout without needing an additional sugar boost. A high-glycemic snack immediately before or during these shorter runs is generally unnecessary and can sometimes lead to a sugar crash. If you feel the need for a snack, a balanced option with slower-digesting carbs is better.
For Long Runs (over 60 minutes)
Endurance events lasting over an hour require a consistent fuel source to prevent glycogen depletion. In these cases, a strategic intake of fast-acting sugar becomes beneficial. Sports dietitians often recommend consuming simple carbohydrates during the run itself, with a target of 30–60 grams per hour for many athletes. This could start about 45-60 minutes into the run to top off stores.
For High-Intensity Workouts
For high-intensity sessions like intervals or tempo runs, consuming a fast-acting carb source 15-30 minutes before the workout can help ensure your muscles have a readily available fuel source. This timing can prevent the initial drop in blood sugar and provide the immediate energy needed for a sustained high effort.
Comparison Table: Timing and Type of Sweet
| Run Type | Timing Before Run | Recommended Sweet Examples | Why It Works |
|---|---|---|---|
| Short/Easy Run (<60 min) | No immediate sugar needed. If hungry, 1-4 hours prior, eat a balanced meal. | Whole fruits (banana), toast with nut butter. | Provides steady, sustained energy without rapid blood sugar spikes. |
| Long Run (>60 min) | Small, easily digestible snack 30-60 minutes before. Continued fuel during the run. | Energy gels, sports chews, small candies (jelly beans, gummies) during the run. | Rapidly absorbed to provide a quick and steady supply of glucose as muscle glycogen is depleted. |
| High-Intensity Workout | 15-30 minutes before or during for sessions over 60 minutes. | Energy gels, chews, or a small piece of easily digestible candy. | Ensures a quick jolt of glucose is available to fuel peak performance during high-intensity intervals. |
How to Choose the Right 'Sweet'
Not all sugary foods are created equal when it comes to pre-run fueling. The best choices are those with minimal fiber, fat, and protein, which can slow digestion and cause stomach upset during exercise.
- Good Options: Simple sugars found in energy gels, sports chews, dried fruits (like dates or raisins), and certain candies (such as jelly babies or gummies) are effective because they are quickly absorbed. A banana is also an excellent choice due to its high carbohydrate content and potassium.
- Avoid These: Sugary items high in fat and fiber, such as chocolate bars, cookies, or pastries, should be avoided immediately before a run. These can cause digestive distress and delay the energy boost you need.
Conclusion: Finding Your Sweet Spot
Knowing when to eat a sweet before running is an individualized process that requires experimentation during training runs. A small, fast-acting carbohydrate snack can be an effective way to top off glycogen stores for long or high-intensity efforts, while short, easy runs may not require a pre-workout sweet at all. The key is to test different strategies to see what works best for your body, paying attention to timing, portion size, and the type of sugar. By using sugar strategically, you can harness its power to improve your energy and performance, rather than risking a debilitating crash.
Resources
- The American College of Sports Medicine offers comprehensive guidelines on athlete nutrition and carbohydrate intake for various activities.
The Role of Electrolytes and Hydration
While focusing on carbohydrate intake is important, especially for longer or hotter runs, it's also vital to consider hydration and electrolyte balance. Many energy gels and chews contain added electrolytes, but if you're relying on regular candy, you'll need to replenish sodium and potassium separately, perhaps with a sports drink or salt tabs. Ignoring hydration can lead to cramps and hinder performance, even with a perfect fueling strategy. Listen to your body and ensure you're hydrating consistently, especially on warmer days or during high-intensity efforts.
Training Your Gut to Handle Sugar
For some runners, digestive issues can be a concern when consuming sugar during a run. The good news is that the gut is adaptable and can be trained, just like your muscles. Start with very small amounts of easily digestible carbs, like a few sips of a sports drink or a single energy chew, and gradually increase the amount over several training runs. This process can help your stomach become more accustomed to processing fuel while you are running, reducing the risk of gastrointestinal problems on race day.
