Carboloading (carbohydrate loading) is a dietary strategy where athletes intentionally increase their carbohydrate intake before a competition. The goal is to maximize glycogen stores in the muscles and liver, ensuring enough energy during the competition and preventing early fatigue.
Can carboloading impact performance?
The answer is yes, but not always unequivocally.
Numerous studies show that carboloading can significantly improve endurance performance. It is especially useful in long-distance competitions, such as marathons, to delay fatigue. Sherman et al. (1981) demonstrated that runners who practiced carboloading were able to maintain optimal performance for a longer time, thanks to fuller and more efficient glycogen stores.
Glycogen is the primary energy source for muscles during intense, prolonged exercise. When glycogen stores are depleted, the body lacks the quick-access energy it needs and must turn to fat reserves, which provide energy less efficiently.
What does optimal carboloading look like?
- Duration and timing
A 24-hour “loading phase” is often sufficient to maximize glycogen stores, according to Bussau et al. (2002). Earlier recommendations to load several days before a competition are considered outdated. - Amount and quality of carbohydrates
Carboloading requires around 8-10 grams of carbohydrates per kilogram of body weight per day, ideally from complex carbohydrates such as whole grains and rice, to keep blood sugar levels stable. - Gender differences
Studies like the one by Tarnopolsky et al. (1995) show that women store less glycogen than men during carboloading unless they increase their caloric intake. To achieve similar benefits as men, women should consume about 30% more calories during this phase, which means not only more carbohydrates but more total energy. Additionally, women have a higher capacity to store glycogen during the follicular phase (the time between the start of the period and ovulation), making carboloading more effective in this period.
Criticism of carboloading
Not all athletes benefit equally from carboloading. Some studies question its advantages in specific situations:
- Well-trained athletes and shorter distances
Rauch et al. (1995) found that well-trained athletes benefit less from carboloading because their glycogen stores are already efficient. For shorter distances, where carbohydrate stores are not fully depleted, carboloading has little effect. - Side effects like weight gain
Hawley et al. (1997) explained that carboloading leads to water retention. Each gram of glycogen binds about 3-4 grams of water, causing a temporary weight gain of 1-2 kg, which some runners find bothersome. Additionally, drastically increasing carbohydrate intake can cause gastrointestinal issues.
Conclusion
Carboloading can be an effective way to boost performance in long-endurance events like marathons, as it maximizes glycogen stores in muscles and the liver, delaying fatigue. It is especially beneficial for competitions lasting over 90 minutes, helping maintain performance and ensuring a steady energy supply.
However, carboloading is not equally effective for everyone. Well-trained athletes and runners competing over shorter distances benefit less, as their glycogen stores are already efficiently filled. Side effects like temporary weight gain from water retention and digestive issues can also occur.
For women, it’s essential to increase caloric intake by about 30% during the loading phase to achieve similar effects as men.