Understanding the Limits: How many carbs can your body absorb at once?

January 13, 2026 •

4 min read

In a healthy adult, the body can store approximately 500 grams of carbohydrates as glycogen in the muscles and liver. Understanding precisely how many carbs can your body absorb at once is critical for optimal fueling, as consuming excess can lead to gastrointestinal distress and wasted energy, particularly for endurance athletes.

Quick Summary

The body's rate of carbohydrate absorption is limited by intestinal transporters. A common endurance fueling strategy uses a glucose-fructose mix to maximize intake, though individual gut tolerance varies. Exceeding this capacity can cause GI upset.

Key Points

90g/hr Limit: The human body can absorb a maximum of about 90 grams of carbohydrates per hour during intense exercise, typically achieved by combining different types of sugar.
Two Transport Systems: Absorption relies on separate intestinal pathways for glucose (~60g/hr via SGLT1/GLUT2) and fructose (~30g/hr via GLUT5).
Glucose-Fructose Ratio: An optimal 2:1 ratio of glucose to fructose is recommended for athletes to maximize carbohydrate oxidation and absorption rate.
Gut Training is Essential: Athletes can train their digestive system to tolerate higher carbohydrate loads by practicing their fueling strategy during long training sessions.
Risk of GI Distress: Exceeding the absorption limit leads to unabsorbed carbs fermenting in the colon, causing bloating, gas, and potential diarrhea.
Absorption Varies: Factors like carbohydrate type, fiber content, and the presence of fat and protein in a meal all influence the rate of absorption.
Storage Capacity: After absorption, glucose is stored as glycogen, with muscles holding around 400g and the liver about 100g in a healthy adult.

The Absorption Mechanism: Intestinal Gatekeepers

The journey of carbohydrates from your plate to your muscles is a complex process. It begins with digestion, breaking down complex starches and sugars into simple sugars (monosaccharides) like glucose, fructose, and galactose. The final stage of this journey is absorption, which occurs primarily in the small intestine and relies on specialized protein transporters to move these monosaccharides into the bloodstream.

There are two main transporter systems to understand:

SGLT1 and GLUT2: These transporters are responsible for moving glucose and galactose across the intestinal wall. The SGLT1 transporter becomes saturated at a rate of roughly 60 grams of glucose per hour, creating a historical ceiling for single-source carbohydrate intake.
GLUT5: This transporter facilitates the movement of fructose. Since fructose uses a separate pathway, it can be absorbed simultaneously with glucose, effectively bypassing the glucose-only limitation. The GLUT5 pathway caps out at around 30 grams of fructose per hour.

The 90g/hr Standard for Athletes

For endurance athletes, combining glucose and fructose in a specific ratio is a proven strategy to maximize absorption. Research from the early 2000s established the 2:1 glucose-to-fructose ratio as an optimal blend to push the carbohydrate absorption rate to approximately 90 grams per hour without significantly increasing gastrointestinal distress. This strategy effectively leverages both intestinal transporter pathways simultaneously.

Beyond 90g/hr: The New Frontier

While 90 grams per hour has long been the gold standard, some elite athletes report tolerating higher intake rates, with newer studies exploring regimens of up to 120 grams per hour. This is thought to be possible through "gut training," a process where the digestive system adapts to higher carbohydrate loads through consistent practice. However, some research suggests that higher intakes might not always translate to better performance and could increase metabolic stress. For most non-elite athletes, sticking to the 90g/hr guideline is more than sufficient and safer.

Factors Influencing Absorption Rate

Your personal carbohydrate absorption rate is not a fixed number and is influenced by several factors:

Type of Carbohydrate: Simple sugars like glucose and fructose are absorbed much faster than complex carbohydrates, which require more extensive breakdown. The combination of different simple sugars also impacts absorption. For example, glucose and galactose are absorbed faster than fructose.
Presence of Other Macronutrients: Consuming carbohydrates with fiber, fat, and protein significantly slows down the rate of digestion and absorption. While beneficial for stable energy levels in daily nutrition, this effect is undesirable for rapid fueling during intense exercise.
Exercise Intensity and Duration: During high-intensity exercise, the digestive system's capacity can be compromised, as blood is shunted away from the gut to working muscles. This is why easily digestible sources like gels and drinks are preferred during long events over solid foods.
Gut Microbiota and Training Status: The composition of your gut bacteria can influence digestion. Moreover, athletes who consistently practice fueling during training can improve their digestive system's tolerance and absorption capacity over time.
Individual Variation: Everyone's physiology is different. Factors like baseline digestive enzymes and the health of the intestinal mucosa play a role in absorption efficiency.

Carbohydrate Type and Absorption Comparison


Feature	Simple Carbohydrates (e.g., Glucose, Fructose)	Complex Carbohydrates (e.g., Starches)
Digestion Speed	Rapid, require minimal digestion.	Slow, requires extensive enzymatic breakdown.
Absorption Rate	Very fast, enter bloodstream quickly.	Slow, gradual release into bloodstream.
Blood Sugar Impact	Can cause rapid spikes, providing quick energy.	Leads to a more sustained, slower rise in blood glucose.
Best For	Fueling during intense exercise, immediate post-exercise recovery.	Daily nutrition, sustained energy, pre-exercise meals.
Primary Source	Sports drinks, gels, honey, fruit juice.	Whole grains, vegetables, legumes, whole fruits.
Exercise Context	Ideal for meeting high energy demands during long events (>90 mins).	Primarily used for general health and pre-event carb-loading meals.

What Happens When You Over-consume Carbs?

If you consume carbohydrates faster than your small intestine can absorb them, the excess remains in the gut and is passed to the colon. Here, colonic bacteria begin to ferment the unabsorbed carbohydrates, producing gas and short-chain fatty acids. This process leads to unpleasant gastrointestinal distress, including:

Abdominal bloating and cramping
Nausea
Excessive gas
Diarrhea, which can accelerate dehydration

These symptoms can severely impact athletic performance and overall comfort. For this reason, it is essential to train with your fueling strategy and find the maximum intake rate your body can handle comfortably.

Conclusion: Personalize Your Fueling Strategy

While the general consensus points to a maximum absorption rate of around 90 grams of carbohydrates per hour using a glucose-fructose blend, this is not a hard-and-fast rule. An individual's absorption capacity is influenced by numerous factors, including carb type, gut health, and training status. For endurance athletes, implementing a gut-training strategy during long training sessions is essential for determining a personal tolerance level and minimizing the risk of GI issues on race day. For general health and daily fueling, a mix of simple and complex carbs, along with fiber, protein, and fat, promotes more stable energy and prevents absorption bottlenecks. By understanding these limits and customizing your approach, you can optimize your energy intake for better performance and digestion.

For more detailed guidance on endurance fueling, review the contemporary perspectives provided by the Gatorade Sports Science Institute.

Frequently Asked Questions

If you consume more carbohydrates than your small intestine can absorb, the unabsorbed carbs pass into the large intestine. There, bacteria ferment them, producing gas and causing gastrointestinal issues like bloating, cramping, and diarrhea.

While 90g/hr is the long-established limit using a 2:1 glucose-fructose mix, some elite athletes have shown tolerance for higher intakes, up to 120g/hr, through extensive 'gut training.' However, this strategy may not be beneficial or tolerable for most individuals.

Yes, dietary fiber slows down the digestion and absorption of carbohydrates. This results in a more gradual release of glucose into the bloodstream and helps prevent rapid blood sugar spikes.

Gut training involves consistently practicing high carbohydrate intake during long training sessions. This helps the digestive system adapt and become more efficient at absorbing large amounts of carbohydrates with less gastrointestinal discomfort.

Complex carbohydrates like starches are broken down more slowly and absorbed gradually, whereas simple carbs like glucose and fructose are absorbed very quickly. This difference is crucial for timing your fueling needs, especially during exercise.

For exercise lasting over 90 minutes, you can improve absorption by combining glucose and fructose sources (like in a 2:1 ratio) and by gradually increasing your intake during training to build tolerance.

No. Carbohydrates are used for immediate energy needs first. Any excess glucose is stored as glycogen in the liver and muscles, up to their storage capacity. Once those stores are full, further excess is converted to fat.