What is inside an energy gel? A deep dive into endurance fuel

November 19, 2025 •

4 min read

For endurance events lasting over 90 minutes, your body's stored glycogen begins to run low, leading to fatigue. Understanding what is inside an energy gel is crucial for replenishing those fuel stores, maintaining performance, and avoiding the dreaded 'bonk'.

Quick Summary

Energy gels contain a powerful blend of carbohydrates for quick and sustained energy, electrolytes to maintain hydration, and sometimes caffeine or amino acids for an added performance boost. Water, flavorings, and preservatives are also standard components.

Key Points

Carbohydrate Blend: Most gels use a mix of fast-absorbing maltodextrin and fructose to deliver quick, sustained energy and maximize absorption.
Electrolytes are Crucial: Key minerals like sodium and potassium are added to replenish salts lost through sweat, maintaining hydration and muscle function.
Caffeine for Performance: Many gels include caffeine to boost focus and reduce the perception of fatigue, which is useful during the later stages of long events.
Isotonic vs. Standard Gels: Isotonic gels contain added water for easier digestion without extra fluid, while standard gels are more concentrated and must be consumed with water.
Beyond the Basics: Some gels add BCAAs to help protect muscle tissue during ultra-endurance efforts or use natural sources like honey and maple syrup instead of processed carbs.
Test in Training: Athletes should try different gels during training to find which type and flavor best suit their digestive system and fueling strategy.

The Core Components: Carbohydrates

At the heart of every energy gel are carbohydrates, the body's primary fuel source during high-intensity exercise. Manufacturers blend different types of carbs to provide both immediate and sustained energy release.

Maltodextrin: The Fast-Absorbing Carb

Maltodextrin is a complex carbohydrate, essentially a chain of glucose molecules, that is rapidly digested and absorbed into the bloodstream. This provides a quick and easily utilized source of energy for your muscles. Since it's less sweet than simple sugar, it can be a good choice for athletes who find gels overly saccharine.

Fructose and Glucose: The Simple Sugars

Many gels pair maltodextrin with simple sugars like fructose and glucose. Fructose is absorbed via a different pathway than glucose, allowing the body to process a higher total volume of carbohydrates per hour without overwhelming the digestive system. Research suggests that a glucose-to-fructose ratio of 1:0.8 to 2:1 can maximize carbohydrate absorption and utilization. This 'multi-transportable carbohydrate' approach is a cornerstone of modern sports nutrition.

Natural Carbohydrate Alternatives

For athletes seeking a more natural option, some gels use whole-food ingredients as their carbohydrate source. Common examples include:

Honey: Rich in fructose and glucose.
Maple Syrup: Primarily sucrose, which is one part glucose and one part fructose.
Brown Rice Syrup: Another natural sugar blend.

The Supporting Cast: Electrolytes and Water

Beyond just carbs, energy gels include other crucial components for optimal performance.

Replenishing Lost Minerals with Electrolytes

Sweating during exercise causes the body to lose vital minerals, known as electrolytes, which are essential for nerve and muscle function. Energy gels contain key electrolytes like sodium and potassium to help replenish these losses and maintain fluid balance. A sufficient level of sodium is particularly important for promoting fluid retention and preventing issues like hyponatremia during long events.

Water: Crucial for Absorption

Most gels are highly concentrated and require water to be consumed alongside them for proper digestion and absorption. Consuming a hypertonic gel without water can pull fluid into your gut, leading to stomach cramps or bloating. Isotonic gels, which have a thinner consistency, are formulated with additional water and don't require extra fluid for absorption, minimizing the risk of gastric distress.

Performance Boosters and Additives

Some gels incorporate extra ingredients to provide additional performance benefits.

Caffeine for a Mental Edge

Caffeinated gels are designed to provide a physical and mental boost, reducing the perception of effort and improving focus, especially during the later stages of a race. Caffeine levels vary significantly between gels, so athletes should test their tolerance in training to avoid jitteriness or stomach upset.

Amino Acids to Protect Muscles

Found most often in gels for ultra-endurance athletes, branched-chain amino acids (BCAAs) like leucine, isoleucine, and valine are sometimes added. During long, strenuous exercise, the body can start breaking down muscle protein for fuel. BCAAs may help reduce muscle damage and delay mental fatigue in these scenarios.

Flavors, Thickeners, and Preservatives

To make gels palatable and give them a long shelf life, manufacturers include several other ingredients:

Flavorings: Often derived from fruit juice concentrates or natural/artificial flavors to improve taste.
Thickeners: Gelling agents like gellan gum or xanthan gum create the desired gel-like consistency.
Acidity Regulators: Ingredients like citric acid or sodium citrates are used for flavor and preservation.
Preservatives: Potassium sorbate and sodium benzoate are common choices to maintain freshness and safety.

Comparison of Energy Gel Types


Feature	Standard Gel	Isotonic Gel	Natural Gel
Carbohydrate Source	Maltodextrin, Fructose	Maltodextrin, Fructose	Honey, Maple Syrup, Fruit Puree
Water Required	Yes	No	Varies (often recommended)
Consistency	Thick, Syrupy	Thin, Liquid-like	Jam-like, Paste-like
Electrolytes	Present, often low	Often enhanced	Present (e.g., sea salt)
Additives	Common (preservatives, flavors)	Common (preservatives, flavors)	Minimal or none
Stomach Tolerance	Can cause issues without water	Gentle on the stomach	Typically well-tolerated
Convenience	Highly portable, small packet	Very easy to consume on the move	Varies by packaging

Choosing the Right Gel for You

Selecting the right energy gel involves understanding your individual needs and tolerance. For a quick energy burst during a standard race, a classic gel with a 2:1 glucose-fructose ratio may suffice, provided you take it with water. If you're running in the heat or have a sensitive stomach, an isotonic gel could be a better option. For ultra-endurance events, you might opt for a gel with added electrolytes or amino acids. It is always wise to experiment with different brands and types during training to see what your body tolerates best and when to take them for maximum benefit.

For those interested in making their own, DIY recipes often use a mix of maple syrup or honey for energy, blended with fruit purees and a pinch of salt for electrolytes. While these offer more control over ingredients and avoid artificial additives, they require preparation and proper storage.

Conclusion: More Than Just Sugar

In short, the answer to "what is inside an energy gel?" is a scientifically formulated blend of ingredients designed to deliver fast, efficient fuel during exercise. The core is a mix of simple and complex carbohydrates, balanced with electrolytes and water for effective absorption and hydration. Optional ingredients like caffeine and amino acids can further tailor the gel to specific performance needs. By understanding these components, athletes can make informed choices to optimize their fueling strategy and push their limits with confidence. For further reading on sports fueling strategies, see the detailed guides available on sites like TrainingPeaks.

Frequently Asked Questions

The primary ingredient is a blend of carbohydrates, typically maltodextrin (a complex carb) and fructose (a simple sugar), designed for quick and efficient energy delivery.

Combining different carbohydrates like glucose and fructose allows the body to absorb more fuel per hour. This approach, known as multi-transportable carbohydrates, maximizes energy uptake by utilizing different absorption pathways.

Yes, unless it is an isotonic gel. Standard gels are concentrated and require water for proper digestion and absorption. Consuming a concentrated gel without water can cause stomach upset.

Caffeine is added to some energy gels to increase mental alertness, improve focus, and reduce the perception of effort. It is particularly useful for an extra boost in the final stages of an endurance event.

Electrolytes are essential minerals like sodium and potassium that are lost through sweat. They are included in gels to help maintain the body's fluid balance and proper muscle function, preventing cramps and dehydration.

Neither is inherently 'better.' Natural gels use whole-food ingredients like honey or maple syrup, which are appealing to some for their minimal processing. Synthetic gels are formulated for maximum performance and digestibility. The best choice depends on individual preference and tolerance.

For workouts under an hour, most people do not need energy gels as their body's glycogen stores are sufficient. Gels are most beneficial for endurance activities lasting longer than 60-90 minutes.