Carb loading is a strategy employed by athletes to enhance their endurance and performance in events lasting longer than 90 minutes. This involves increasing carbohydrate intake in the days leading up to an event while simultaneously reducing training intensity. The goal is to maximize glycogen stores in the muscles and liver, providing a readily available energy source during prolonged exertion.
What is Carb Loading?
Carb loading is a performance nutrition strategy where you eat more carbohydrates leading up to exercise or an event, with the goal of enhancing your performance,” says Lexi Moriarty, RDN, a registered dietitian and certified specialist in sports dietetics at Fueled + Balanced Nutrition. “This helps to maximize the amount of glycogen, or stored energy, in the muscles and liver that's available for use during exercise.” The purpose behind this strategy is to increase glycogen stores in your muscles and liver, potentially leading to greater athletic endurance and delayed fatigue. Endurance athletes may deliberately boost their carbohydrate intake in the days leading up to an endurance competition or event.
Who Benefits from Carb Loading?
Carb loading is most beneficial for endurance athletes competing for more than 90 minutes. It is primarily suited for individuals participating in challenging physical events, such as:
- Long-distance running (half or full marathons)
- Long-distance cycling
- Long-distance swimming
- Triathlons
Carb loading is not necessary for regular workouts like a Pilates class or a 30-minute jog.
How Carb Loading Works
Carbohydrates are stored in the body as glycogen, primarily in the liver and muscles. During moderate to high-intensity workouts, the body utilizes these glycogen stores as its primary energy source. Carb loading aims to increase these glycogen stores above the normal amount by increasing carbohydrate consumption and decreasing exercise for several days before an event.
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Benefits of Carb Loading
Carb loading can help endurance athletes prepare for race day or another fitness competition by boosting glycogen stores, which could translate to improved performance and recovery.
- Improved Race Times: Carb loading allows you to maintain your pace longer without fatiguing due to the larger amount of glycogen energy available. Carb loading can provide a 2-3 percent performance increase for exercise longer than 90 minutes.
- Increased Stamina: Enhancing glycogen reserves via carb loading can help to postpone fatigue, enabling athletes to sustain higher intensity and endurance activities for more extended durations of time.
- Aiding Recovery: Carb loading tops off those glycogen stores, so you’re less likely to be totally depleted post-event.Replenishing glycogen stores is crucial for preparing the body for subsequent training sessions or competitions.
Carb Loading Strategies
There are several approaches to carb loading, varying in duration and intensity.
1-Day Carb Loading
This approach is suitable for shorter, less intense forms of exercise like a half marathon or triathlon. One day before the event, avoid exercise and consume a carb-rich diet, aiming for about 10-12 grams of carbohydrates per kilogram of body weight.
3-Day Carb Loading
During a classic 3-day carb loading approach for longer distance events, athletes typically consume at least 70 percent of their standard daily calories in the form of carbohydrates while simultaneously drastically reducing physical activity. Experts generally recommend this approach for a full marathon or long-distance triathlon.
6-Day Carb Loading
For distance events like an Ironman, some professionals recommend carb loading for as many as 6 days prior to the race. During a 6-day program, athletes generally maintain exercise while consuming a low-carb diet (about 15 percent of their standard total calories) to decrease glycogen stores during those initial three days. Then, three days prior to the race, they boost carbohydrate consumption to as much as 70 percent of their total calories while simultaneously reducing physical activity.
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What to Eat During Carb Loading
When carb loading, choose foods lower in fat and protein and high in complex carbohydrates. Think wholesome carbs, fruits, and vegetables like the following:
- Pasta
- Quinoa
- White or whole-grain bread
- White or brown rice
- Smoothies, especially those containing bananas and citrus
- Potatoes (peeled) or sweet potatoes
- Carrots
- Corn
- Peas
- Applesauce
- Pretzels
- Low-fiber cereals
- Fruit juices
Foods to Limit During Carb Loading
Limit high-fiber and high-fat foods, which might lead to gastrointestinal discomfort, including bloating and diarrhea on race day.
Some foods to consider limiting while you’re carb-loading (even if they technically contain carbs!) include:
- Pizza
- Candy
- Pastries
- Creamy sauces
- Doughnuts
- Energy bars
- Ice cream
- Chips
- Beans
- Cookies
- French fries
- Oatmeal
- Cruciferous vegetables
- Alcohol
- Caffeine
Common Carb Loading Mistakes
- Carelessly Carb Loading: Eating a large volume of food, rather than mapping out meals and snacks that come with the (beneficial) carbs you need.
- Laser-Focusing on Carbs Alone: Forgetting to consider things that can actually deter their performance goals, like not consuming enough protein or not staying adequately hydrated.
- Introducing New Foods: Introducing any new foods when you’re carb loading can lead to digestive issues.
- Consuming Too Much Fat: Consuming too much fat in the process, which may lead to adverse results like gastrointestinal discomfort or impeded performance levels.
- Consuming Too Much Fiber: Eating too much fiber can also cause unwanted side effects like bloating, diarrhea, and general intestinal distress.
- Exercising Too Much: Exercising too much prior to their event, which limits the extent of glycogen, or stored carbohydrates, to be in effect-even with a high-carbohydrate diet
- Saving All Carbs for Dinner: Don't jam-pack a day’s worth of carbs in at dinnertime.
- Not Properly Hydrating: Staying hydrated is always important, but it’s especially crucial when you’re carb loading.
Potential Risks and Considerations
While carb loading can be safe for most endurance athletes, it's essential to be aware of potential risks and considerations.
- Diabetes: Individuals with diabetes should consult their physician before starting a carb loading regimen due to the increased carbohydrate intake.
- Weight Gain: As the body stores glycogen, it also stores water, leading to potential weight gain and feelings of bulkiness.
- Digestive Issues: Digestive complaints and bloating are common due to the high fiber content of many carbohydrate-rich foods.
- Individual Variability: The effectiveness of carb loading can vary depending on individual factors, such as metabolism, training level, and event type.
The Science Behind Carb Loading
Research supports the benefits of carb loading for endurance performance. Carbohydrate supplementation has been associated with shorter exercise times in submaximal exercise followed by a time trial. Studies have also shown that carbohydrate loading can lead to a significant increase in mean power output.
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