Who is Most Likely to Benefit from Carbohydrate Loading?

October 16, 2025 •

4 min read

Research indicates that carbohydrate loading can improve endurance performance by 2–3% and delay fatigue for activities over 90 minutes. This makes understanding who is most likely to benefit from carbohydrate loading? a critical part of a successful race-day nutrition strategy.

Quick Summary

Carbohydrate loading primarily helps endurance athletes in prolonged events by maximizing muscle and liver glycogen stores. The strategy is generally unnecessary for shorter duration or lower-intensity exercises, which can lead to negative side effects.

Key Points

Endurance Athletes: The primary beneficiaries are athletes competing in events lasting 90 minutes or longer, such as marathons, triathlons, and long-distance cycling.
Maximizes Glycogen Stores: The strategy works by supercompensating the body's muscle and liver glycogen stores, providing a larger energy reserve.
Delays Fatigue: Maximizing glycogen helps delay the onset of fatigue, often referred to as 'hitting the wall' during prolonged exercise.
Not for Short Events: Carb loading is not necessary for shorter events (under 90 minutes) or low-intensity workouts, where a standard, balanced diet provides sufficient energy.
Consider Side Effects: Be aware of potential side effects like bloating, digestive discomfort, and temporary water-weight gain. Practicing the protocol during training is advised.
Requires a Taper: To be effective, carb loading must be combined with a reduction in training volume, or a 'taper,' in the days leading up to the event.
Focus on Low-Fiber Carbs: For loading, prioritize easily digestible, lower-fiber carbohydrates like white rice, pasta, and sports drinks to avoid gastrointestinal issues on race day.

Carbohydrate loading, or 'carb-loading,' is a dietary strategy that has been a cornerstone of endurance sports for decades. Its primary goal is to maximize the amount of glycogen, the stored form of carbohydrates, in the muscles and liver before a demanding physical event. This supercompensation of glycogen stores provides a larger 'fuel tank' for the body to draw upon, helping to delay the onset of fatigue. However, this technique is not a one-size-fits-all solution and is most effective for a specific group of athletes.

The Physiological Rationale Behind Carb Loading

To understand who benefits, it's essential to grasp how the body uses fuel during exercise. During moderate to high-intensity physical activity, the body primarily relies on carbohydrates for energy. These carbohydrates are stored as glycogen within the muscle tissue and the liver. The body's capacity to store glycogen is limited, providing enough energy for approximately 90 minutes of vigorous activity. Once these glycogen stores are depleted, a phenomenon known as 'hitting the wall' occurs, characterized by severe fatigue and a drastic drop in performance.

Carbohydrate loading aims to increase these reserves above normal levels. By consuming a higher-than-usual carbohydrate intake in the days leading up to an event, combined with a tapering of training volume, athletes can ensure they start their race with a full tank. This can extend the duration of sustained performance and postpone fatigue, giving the athlete a significant competitive edge.

Who Is the Ideal Candidate for Carbohydrate Loading?

The most prominent beneficiaries of carbohydrate loading are endurance athletes engaged in continuous, high-intensity events lasting 90 minutes or longer.

Marathon Runners: A full marathon (26.2 miles) typically takes well over 90 minutes for most participants. Carb loading ensures runners have sufficient fuel to maintain their pace and power through the later stages of the race, preventing the dreaded 'bonk'.
Triathletes: Events like Ironman or longer-distance triathlons involve swimming, cycling, and running for many hours. Maximizing glycogen stores is crucial for sustaining energy throughout all three disciplines.
Long-Distance Cyclists: For multi-hour bike races or long-distance rides, a carb-loading strategy is highly effective in providing the necessary energy reserves.
Long-Distance Swimmers: Similar to running and cycling, prolonged swimming events will deplete glycogen stores, making a pre-event loading phase beneficial.
Tournament Athletes: In sports like soccer or basketball with back-to-back games or intense tournament formats, carb loading can help replenish glycogen stores quickly between closely spaced events.

Who Does Not Require Carb Loading?

Conversely, several groups of athletes or individuals will find little to no benefit from carb loading, and may even experience negative side effects.

Shorter-Duration Activities: For events lasting less than 60-90 minutes, such as a 5K race, a standard gym workout, or weightlifting, the body's normal glycogen stores are typically adequate. The focus for these activities should be on consistent daily nutrition rather than a specific loading protocol.
Intermittent Sports: Athletes in sports with short bursts of activity, like sprinting, or those with frequent rest periods, will not see significant performance gains from carb loading. Their energy systems are less reliant on maxed-out glycogen reserves.
Casual Exercisers: Individuals who are not competing or training for specific long-distance events do not need to carb-load. Adopting a high-carb diet without the matching expenditure will lead to unnecessary weight gain.

Side Effects and Considerations

While beneficial for the right circumstances, carb loading is not without potential drawbacks. Short-term weight gain, typically 2-4 lbs, is common due to the water retained by the stored glycogen. This can be disconcerting for some athletes but is a sign that the loading is working. Other side effects can include bloating and digestive discomfort, especially when consuming large quantities of high-fiber carbs. Athletes with diabetes must consult a physician before attempting carb loading, as it can impact blood sugar levels. Practicing the carb-loading protocol during training is highly recommended to identify and mitigate any adverse reactions before race day.

Practical Carbohydrate Loading Strategies

Modern approaches to carb loading have moved away from the extreme 'depletion-loading' phase. A more practical and effective method involves a high carbohydrate intake (8-12 grams per kg of body weight) combined with an exercise taper in the 1-3 days before the event. A focus on lower-fiber carbohydrate sources like white rice, pasta, and potatoes can help avoid digestive upset on race day. Liquid carbohydrate sources, like sports drinks and juices, can also help meet the high carbohydrate targets without causing excessive fullness.

Carb Loading vs. Daily Fuelling


Feature	Carb Loading for Endurance Athletes	Regular Fuelling for Shorter/Less Intense Activity
Carb Intake	8–12g per kg body weight in 1-3 days before event	Consistent, balanced intake to meet daily energy needs
Fuel Stores	Maximizes muscle and liver glycogen stores	Normal glycogen levels are sufficient
Exercise Duration	Primarily for events > 90 minutes	No specific duration requirement
Training Taper	Essential to allow glycogen storage	Not necessary
Risk	Potential for bloating, water retention, and weight gain	Minimal risk; avoids excess calorie intake
Effectiveness	Significant performance improvement for specific events	No significant performance benefit

Conclusion

In summary, the answer to who benefits most from carbohydrate loading is clear: endurance athletes competing in events that last longer than 90 minutes. For these individuals, maximizing glycogen stores offers a distinct advantage by extending the time to fatigue and enhancing performance. However, for those engaging in shorter, less intense exercise, carb loading is unnecessary and potentially counterproductive. By understanding the science and tailoring the approach to the specific demands of the event, athletes can leverage this nutritional strategy for optimal results. A final key takeaway is to practice any fuelling plan, including carb loading, during training to ensure it works effectively for your body before relying on it for a major competition.

Frequently Asked Questions

The primary benefit of carbohydrate loading is the maximization of muscle and liver glycogen stores, providing a larger energy reserve that can significantly delay fatigue during long-duration endurance events.

Carbohydrate loading is most effective for endurance events that last 90 minutes or longer, such as marathons, long-distance triathlons, and cycling races.

No, carbohydrate loading is not necessary for a 5K race. The body's normal glycogen stores are sufficient for shorter events, and excessive carbs may cause discomfort without providing a performance benefit.

Most modern protocols recommend beginning the high-carbohydrate intake phase 1 to 3 days before the event, in conjunction with tapering your exercise.

The temporary weight gain associated with carb loading is due to the extra water that is stored alongside the additional glycogen in your muscles. This is a normal and expected part of the process.

While high-fiber foods are generally healthy, it's advisable to focus on lower-fiber carbohydrate sources during the carb-loading period. High fiber can cause gastrointestinal distress, bloating, and discomfort during the race.

Carbohydrate loading is not beneficial for typical strength training sessions. Muscle glycogen is important, but for high-volume lifting, a consistent daily intake is more appropriate than a pre-event load.

Some research suggests there might be gender-based differences in glycogen storage capacity and hormonal influence. However, the general principles of increasing intake to 8-12g/kg body weight during a taper apply to both genders.

Without proper carbohydrate loading, your glycogen stores may not be maximized, increasing the risk of 'hitting the wall' and experiencing a performance drop or severe fatigue in the later stages of a long race.