Understanding what goes into an energy gel matters as much as understanding how it is used. Ingredients determine not only how much energy is delivered, but how well that energy is absorbed, tolerated, and sustained during prolonged exercise. This article breaks down the key components commonly found in energy gels, explaining what each ingredient does, why it is included, and how formulation choices influence performance and gut comfort. For a broader overview of endurance fueling strategy, see the complete guide to energy gels and endurance fueling.
What Is an Energy Gel?
An energy gel is a concentrated source of carbohydrates, typically delivered in a semi-liquid form to allow rapid digestion and absorption during exercise.
Most energy gels contain:
-
20–30 g of carbohydrate per serving
-
Water to aid absorption
-
Electrolytes, usually sodium
-
Sometimes caffeine or amino acids
Their primary purpose is simple:
to provide fast, usable fuel during prolonged or high-intensity exercise.
Unlike solid foods, gels require minimal chewing and are designed to empty from the stomach quickly, making them practical during running, cycling, and racing.
Why Your Body Needs Fuel During Exercise
Your body stores carbohydrate as glycogen in the muscles and liver. These stores are limited.
Typical glycogen capacity:
-
Muscle glycogen: ~300–500 g
-
Liver glycogen: ~80–100 g
During moderate to high-intensity exercise, especially running, glycogen is the dominant fuel source. At marathon pace, glycogen can be significantly depleted within 90–120 minutes if not replenished.
Once glycogen levels drop too low, athletes experience what is commonly called “the wall” or “bonking”:
-
Sudden drop in power output
-
Loss of coordination
-
Mental fog
-
Dramatic increase in perceived effort
Energy gels exist to slow this depletion and maintain blood glucose levels.
How Energy Gels Work in the Body
When you consume an energy gel during exercise, three key processes occur:
1. Gastric Emptying
The gel must leave the stomach and enter the small intestine. This is influenced by:
-
Osmolality
-
Carbohydrate concentration
-
Type of carbohydrate
-
Presence of fat or protein
Highly concentrated or synthetic gels can slow gastric emptying, increasing the risk of nausea and cramping.
2. Intestinal Absorption
Carbohydrates are absorbed through specific transporters in the gut:
-
SGLT1 for glucose and glucose-based carbs
-
GLUT5 for fructose
Using multiple carbohydrate sources can increase total absorption rates, but only if the gut can tolerate them.
3. Delivery to Working Muscles
Once absorbed, glucose enters the bloodstream and is transported to working muscles where it is oxidised for energy.
If absorption outpaces utilisation, blood sugar spikes. If utilisation outpaces absorption, blood sugar drops. Both impair performance.
Why Carbohydrate Type Matters
Not all carbohydrates behave the same way in the gut.
Common gel carbohydrate sources include:
-
Maltodextrin
-
Glucose
-
Fructose
-
Sucrose
-
Honey
-
Date syrup
Synthetic blends like maltodextrin plus fructose are popular because they allow higher carbohydrate delivery rates. However, they can be problematic for athletes with sensitive stomachs.
Natural sources like honey and date syrup contain:
-
A mix of glucose and fructose
-
Trace minerals
-
Lower processing burden
Research shows that carbohydrate source influences gut comfort, oxidation rates, and perceived exertion, particularly during longer events. For a detailed breakdown of how specific ingredients influence absorption and gut tolerance, see energy gel ingredients explained.
Different carbohydrate sources behave differently in the gut, as explored in honey vs maltodextrin energy gels.
Do Energy Gels Actually Improve Performance?
Yes, when used correctly.
Multiple studies show that carbohydrate ingestion during endurance exercise improves time to exhaustion, maintains power output, preserves cognitive function, and reduces perceived effort, particularly during events lasting longer than 90 minutes.
This relationship between carbohydrate availability and endurance performance has been consistently demonstrated in the sports science literature, including large review papers published in Sports Medicine.
Carbohydrate intake recommendations during endurance events generally range from:
-
30–60 g per hour for events under 2.5 hours
-
Up to 90 g per hour for longer events in trained athletes
These guidelines are based on consensus statements and applied research published in leading journals such as the Journal of Sports Sciences.
However, more is not always better. Overloading the gut with poorly tolerated gels can reduce performance more than under-fueling.
Why Some Athletes Feel Sick From Gels
Common reasons include:
-
High osmolality formulations
-
Excessive fructose intake
-
Artificial sweeteners
-
Lack of water intake
-
Poor gut training
This is why formulation and ingredient simplicity matter. A gel should support performance, not become another variable you have to manage mid-race. Athletes who experience recurring GI issues may benefit from reading best energy gels for sensitive stomachs.
The Bottom Line
Energy gel ingredients are not added arbitrarily. Each component serves a functional purpose, from carbohydrate delivery to hydration support and digestibility. When athletes understand the role of these ingredients, they are better equipped to evaluate fueling options critically and avoid unnecessary complexity. Effective endurance fueling is built on clarity, tolerance, and consistency rather than excess.