Is a high-carb diet good for athletes? Unpacking the science of peak performance

December 30, 2025 •

4 min read

Decades of sports nutrition research have consistently shown that a high carbohydrate diet remains the evidence-based choice for athletes to optimize performance. This approach is central to fueling high-intensity training, replenishing depleted energy stores, and ensuring athletes can perform at their peak day after day.

Quick Summary

A high-carb diet is crucial for athletes, providing the primary energy source needed for strenuous training and competitive performance. This intake is essential for maximizing glycogen stores, delaying fatigue, and accelerating post-exercise recovery across various sports and activities.

Key Points

Essential Fuel: A high-carb diet is the evidence-based approach for providing the primary energy source needed for intense athletic performance.
Glycogen Stores: Carbohydrates are stored as glycogen in muscles and the liver, which is the body's main fuel source during moderate to high-intensity exercise.
Enhanced Recovery: Strategic carbohydrate intake, particularly after exercise, is crucial for replenishing glycogen stores and accelerating recovery between training sessions.
Timing is Key: When and what type of carbs are consumed (pre-workout, during, and post-workout) significantly impacts performance and recovery.
Low-Carb Impairment: Low-carb diets can impair high-intensity performance and slow recovery by limiting crucial glycogen availability.
Tailor Your Intake: Carbohydrate needs should be tailored to the individual athlete, considering their training volume, intensity, and specific sport.

The Fundamental Role of Carbohydrates

Carbohydrates are the body's primary and most efficient fuel source for physical activity, especially for moderate to high-intensity exercise. Upon consumption, they are broken down into glucose, which is then used immediately for energy or converted into glycogen and stored in the muscles and liver. This stored glycogen is the readily available fuel source that powers muscles during training and competition. The limited nature of these glycogen stores means that maintaining a consistent, high carbohydrate intake is essential for athletes to perform optimally and avoid premature fatigue. Restricting this vital macronutrient can compromise performance, training intensity, and recovery.

How Different Athletes Fuel on Carbs

Carbohydrate requirements vary significantly based on an athlete's training volume, intensity, and sport. Instead of a one-size-fits-all percentage, recommendations are typically based on grams per kilogram of body weight per day.

Endurance Athletes: For marathon runners, long-distance cyclists, and triathletes, a high-carb diet is non-negotiable. Their demanding training schedules and lengthy events deplete glycogen stores rapidly. Strategies like 'carb-loading'—increasing carbohydrate intake in the days leading up to a major event—are used to supersaturate glycogen stores, providing a larger reservoir of energy to delay fatigue during the race. Daily intake often falls in the 6–10 g/kg body weight range, and sometimes even higher for extreme events.
Strength and Power Athletes: While protein often takes the spotlight for muscle building, carbohydrates are equally critical. They provide the fuel needed for high-volume resistance training sessions and prevent the body from breaking down muscle tissue for energy. Post-exercise, a combination of carbs and protein is highly effective for replenishing glycogen and initiating muscle repair.
Team Sport Athletes: Sports like soccer, basketball, and hockey involve repeated high-intensity sprints, bursts of acceleration, and constant movement. This intermittent activity pattern is heavily reliant on anaerobic energy systems, which use muscle glycogen at a rapid rate. A high-carb diet ensures adequate glycogen stores to sustain performance throughout a full game and aid recovery for the next training session.

Timing and Types of Carbohydrates

The timing and type of carbohydrates consumed can have a significant impact on athletic performance and recovery.

Pre-Exercise: Eating a carbohydrate-rich meal 3–4 hours before exercise ensures optimal blood glucose levels and topped-up glycogen stores. For a quick boost closer to the event (1 hour or less), easily digestible simple carbohydrates are recommended.
During Exercise: For prolonged events lasting more than 60–90 minutes, ingesting carbohydrates during activity is vital to maintain blood glucose and delay fatigue. Sources like sports drinks, energy gels, and chews are designed for rapid absorption during this time. For events over 2.5 hours, intake can increase substantially to up to 90 grams or more per hour.
Post-Exercise Recovery: The period immediately following exercise is crucial for replenishing glycogen. Consuming carbohydrates within the first 15–30 minutes after intense exercise, ideally with some protein, has been shown to maximize muscle glycogen restoration. This is particularly important when an athlete has another training session or competition within 24 hours.

High-Carbohydrate vs. Low-Carbohydrate Diets for Athletes

While high-carb diets are the gold standard, some nutritional trends promote low-carb, high-fat (LCHF) or ketogenic diets for athletes. The table below outlines the primary considerations for each approach in an athletic context.


Feature	High-Carbohydrate (HC) Diet	Low-Carbohydrate (LC) Diet
Primary Fuel Source	Glycogen (stored carbohydrate) and blood glucose.	Fat stores (fatty acids and ketones).
High-Intensity Performance	Supports and improves performance, especially during moderate to high-intensity activities.	Impairs high-intensity performance by reducing the body's ability to efficiently use carbohydrates for fuel.
Fatigue	Delays the onset of fatigue by ensuring adequate fuel supply.	May cause premature fatigue during intense exercise due to limited carbohydrate availability.
Recovery	Maximizes muscle glycogen resynthesis post-exercise, accelerating recovery.	Delays glycogen resynthesis, which can impede recovery and adaptation for subsequent training sessions.
Training Adaptations	Amplifies training adaptations that are dependent on carbohydrate availability.	Can enhance fat oxidation but may down-regulate carbohydrate utilization enzymes.
Metabolic Flexibility	Supports a flexible metabolism that can shift between carbohydrate and fat oxidation.	Chronic restriction can reduce the capacity for carbohydrate burning.

Recommended High-Carb Food Sources

Incorporating a variety of carbohydrate sources, both complex and simple, is key to meeting an athlete's energy demands.

Complex Carbohydrates (for sustained energy):
- Whole grains (oats, brown rice, whole wheat bread)
- Legumes (lentils, beans, chickpeas)
- Starchy vegetables (potatoes, sweet potatoes, corn)
Simple Carbohydrates (for quick energy and recovery):
- Fruits (bananas, berries, oranges)
- Dried fruit
- Sports drinks, gels, and chews
- Low-fat dairy products

Conclusion

While some niche dietary theories have gained attention, scientific evidence overwhelmingly supports the use of a strategically timed high-carbohydrate diet for most athletes. Carbohydrates are the single most important fuel source for sustaining high-intensity efforts, maximizing endurance, and supporting robust recovery. By focusing on adequate intake of quality carbohydrate sources, athletes can ensure their bodies are properly fueled to meet the demands of their sport. For personalized dietary advice, athletes should consult with a qualified sports nutritionist or dietitian. A well-planned, carb-rich diet, aligned with training demands, is the most effective nutritional strategy for achieving peak athletic performance.

For more detailed guidance on macronutrient timing and intake, see the Journal of the International Society of Sports Nutrition.

Frequently Asked Questions

A high-carb diet is important because carbohydrates are the body's most readily available and efficient fuel source. For athletes performing moderate to high-intensity exercise, these carbs are converted into glycogen, which is stored in the muscles and liver for energy. Without sufficient carbohydrate intake, these glycogen stores become depleted, leading to early fatigue and reduced performance.

If an athlete doesn't eat enough carbohydrates, their body's glycogen stores will not be adequately replenished. This can result in decreased energy, an inability to sustain high-intensity efforts, premature fatigue ('hitting the wall'), slower recovery, and a compromised immune system.

Most athletes, particularly those involved in high-intensity and endurance sports, benefit greatly from a high-carb diet. However, specific needs can vary based on sport, training volume, and individual goals. The intake recommendations range from moderate amounts for less intense exercise to very high amounts for extreme endurance activities.

Carb loading is a strategy used by endurance athletes to maximize their muscle glycogen stores before a major event. It involves increasing carbohydrate intake while reducing training volume for several days. It is most beneficial for endurance events lasting longer than 90 minutes and is generally not necessary for shorter or lower-intensity activities.

For optimal performance, consume complex carbohydrates 3-4 hours before exercise. For quick energy, simple carbs can be taken 1 hour or less beforehand. During prolonged exercise, simple carbs should be consumed regularly. Post-exercise, aim for a mix of simple and complex carbohydrates, ideally with protein, within 30 minutes for rapid recovery.

For competitive athletes, especially those who rely on high-intensity efforts, low-carb diets are generally not recommended. While these diets can increase fat oxidation, they impair the body's ability to efficiently utilize carbohydrates, which can lead to reduced performance and impaired recovery during high-intensity training and competition.

A well-managed high-carb diet is unlikely to cause unwanted weight gain, as athletes' high energy expenditure typically utilizes the excess calories. However, consuming significantly more carbohydrates than required can lead to excess calories, so intake must be periodized and aligned with training volume to balance energy needs.