You’ve probably already seen these tubes or small soft sachets between the fingers of a marathon runner, cyclist, or trail runner. These energy gels, seemingly discreet, are actually invaluable performance allies. They help athletes push back fatigue, maintain their pace, and cross the finish line without collapsing. But what are they really made of? How do they act on our bodies? And why do some people talk about a “2:1 ratio” as a nutritional revolution? If you practice an endurance sport—running, cycling, triathlon, or trail running—this article is for you. We’ll delve into the heart of physiology, science, and real-world experience to understand how a simple energy gel can improve your performance and transform your race.
Why does the body need carbohydrates during exercise?
Before talking about gels, let’s talk fuel. The human body is a machine of fascinating efficiency. But like any machine, it needs energy, and its main fuel is glucose.
Glycogen: your internal battery
The glucose we consume through our diet is stored as glycogen in our muscles (around 400 to 500 g) and in our liver (around 100 g).
This is an internal battery of around 2,000 kcal, which our bodies draw on from the first few minutes of sustained effort. But here’s the problem: this reserve is not infinite. After 1.5 to 2 hours of effort, the tank runs dry… and that’s the famous marathon wall or the bonk in cycling: heavy legs, dizziness, a feeling of emptiness… in short, a difficult finish, potentially even resulting in a DNF.
The body then tries to compensate by burning more fat, but this process is slower and less effective for maintaining a high pace unless you have specifically trained for it.
This is where energy gels come in: they recharge your battery on the go.
Carbohydrate needs during exercise: the golden rule of 30, 60, and 90 g/hour
The research conducted by Asker Jeukendrup (University of Birmingham) and the recommendations of the International Society of Sports Nutrition (ISSN) are clear:
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For efforts lasting less than an hour: no additional carbohydrates needed;
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Between 1 and 2 hours: 30 to 60 g of carbohydrates per hour
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Beyond 2 hours: up to 90 g/h, if the digestive system is well trained.
These figures don’t come out of nowhere: they correspond to the maximum intestinal absorption capacity. And to reach 90 g/h without discomfort, you need to combine two types of sugar, glucose and fructose, hence the famous 2:1 ratio we’ll discuss later.
On average, a gel contains around 25 to 30 g of carbohydrates, so 2 to 3 gels per hour, depending on the duration and intensity of your effort, will be sufficient.
Why consume an energy gel rather than a bar?
Imagine you’re halfway through a marathon. Your watch shows 21 km, your breathing is steady, but your legs are starting to feel heavier. You can feel that the machine isn’t running as smoothly. This is the sign that your glycogen levels decrease. A well-chosen gel, taken at the right time, will help you get back on track.
A concentrated source of fast energy
An energy gel is a concentrated, semi-liquid source of simple and complex carbohydrates. Unlike an energy bar, it doesn’t need to be chewed and is digested very quickly. Absorption begins within minutes, producing an almost immediate effect on blood sugar levels.
Most gels contain:
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Glucose or maltodextrin (a fast-release carbohydrate),
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Fructose (a slow-release carbohydrate),
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Electrolytes (sodium, potassium, magnesium),
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Sometimes caffeine or antioxidants.
This format is designed to be easy to carry, easy to digest, and effective while you’re on the move.
Delaying fatigue, preserving your mental strength
The benefits aren’t only physical. Carbohydrates also fuel the brain: they improve concentration, motivation, and pain management. Studies have shown that simply rinsing your mouth with a sugary solution already activates brain regions associated with performance.
That shows just how strong a signal glucose is for your body: “You can keep going; you have fuel.”
The 2:1 glucose-to-fructose ratio: the winning formula
This is probably the biggest development in sports nutrition over the past ten years.
For a long time, only glucose or maltodextrin was used. The problem is that the intestine can absorb only 60 g of glucose per hour through a specific transporter called SGLT1. Beyond this amount, the sugar remains in the intestine and causes bloating, stomach pain, or even cramps.
However, researchers discovered that fructose uses another transporter called GLUT5. By combining glucose (or maltodextrin) with fructose in a 2:1 ratio, absorption can be increased to 90 g/h (or even higher for elite or highly prepared athletes), while reducing digestive discomfort.
This is the key to modern endurance performance.
The benefits of the 2:1 ratio
- More energy absorbed per hour: up to 50% more than a 100% glucose gel.
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Less digestive stress: better tolerance during prolonged efforts.
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More consistent energy: fewer blood sugar “spikes” and “crashes.”
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Better hydration: lower osmolarity, resulting in better absorption.
A 37 g Mulebar energy gel contains: 18 g of glucose (rice syrup) and 9 g of fructose (agave syrup). Taken every 30 to 40 minutes with water, it helps maintain a steady flow of energy without overwhelming the digestive system. During a marathon, this amounts to 5 or 6 well-spaced gels. During an ultra, alternate them with fruit purées or bars to vary the textures.
How to use an energy gel properly?
An energy gel isn’t a “magic boost.” It should be part of an overall nutrition strategy.
Test it during training
It’s a golden rule: “Never try a gel for the first time on race day.” Every athlete has a different digestive tolerance. Train your stomach as you train your legs. Try several flavors, brands, and dosages.
The ideal timing
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First gel: between 30 and 45 minutes after the start.
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Then, one gel every 30 to 40 minutes, divided into several servings if possible
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Always drink 1 to 2 sips of water after each serving
Never take a gel alone, without water, especially in hot weather: the sugar concentration can slow gastric emptying.
Divide consumption into smaller servings
Rather than consuming an entire gel all at once, try consuming it gradually, in 2 or 3 servings spaced 10–15 minutes apart. This allows:
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More regular absorption,
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Lower risk of reactive hypoglycemia,
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Better digestive comfort.
That is why Mulebar gels are available either in truly resealable (and reusable) tubes or in eco-refills of 12 gels to consume using the 60ml or 150ml silicone flasks.
Adjust the frequency:
| Type of effort | Recommended frequency | Goal |
|---|---|---|
| Intense 10 km | 1 gel at around the 30-minute mark | Maintaining blood sugar levels |
| Half marathon | 1 gel every 7 to 8 km | Avoid “the wall” |
| Marathon | 5 to 6 gels | 60–90g of carbohydrates/h |
| Ultra-trail | 2 gels + 1 compote/h | Energy + slow digestion |
Caffeine or antioxidants: the right gel for every need
Not all gels are created equal. Their composition affects the type of energy they provide, as well as how you feel mentally and physically.
Caffeinated gels: for mental focus and a boost
Caffeine acts as a real “fatigue unlocker.” It stimulates the central nervous system, improves concentration, and reduces the perception of effort. It is recommended for the final stages of a race, moments when your pace drops, and critical sections of a trail race or cycling climb. However, be careful not to overuse it (maximum 2 to 3 caffeinated gels per race) and test them before competition if you are sensitive.
Antioxidant gels: protect and recover
During long efforts, the body produces many free radicals, which cause oxidative stress and muscle micro-inflammation. Antioxidant gels provide nutrients such as vitamin C, zinc, selenium, or fruit extracts rich in polyphenols. The result? Better recovery, less post-race muscle soreness, and a better-preserved immune system.
Neutral gels: simplicity and tolerance
Some athletes prefer to avoid caffeine or strong flavors. “Neutral” gels provide steady energy and maximum tolerance without the risk of feeling sick of the taste.
The most common mistakes:
- Trying a new gel on race day: risk of digestive issues, nausea, and discomfort.
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Forgetting to drink: osmotic concentration too high, slowed digestion.
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Taking a gel before the start: an insulin spike, followed by a slump during the first few kilometers.
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Consuming too many: the intestine can absorb only a limited amount of sugar per hour.
Natural energy gels: a new generation
For a long time, gels were associated with a “chemical” image: artificial taste, gloopy texture, and difficult digestion. Fortunately, a new generation has arrived. Brands like Mulebar have rethought the formula: 100% natural ingredients, sugars from fruit and grains rather than refined sugars, smooth textures even in cold weather, and natural flavors to add enjoyment during exercise.
The result: gels that don’t just provide energy, but also respect your body and performance. Gels that don’t stick, digest well, and therefore fit perfectly into your nutrition strategy.
In conclusion: the fuel for your endurance
When used properly, an energy gel is much more than a simple sugar concentrate.
It’s an intelligent source of energy, calibrated to support your muscles, mind, and digestion during exercise.
The key is strategy: the right ratio (2:1), the right timing, and good digestive tolerance.
Whether you’re preparing for your first marathon or a 100km ultra-trail, remember: energy doesn’t happen by chance; it needs to be planned. And if it can be natural, vegan, and delicious, even better. Because a well-nourished body goes the distance.
FAQ — Frequently asked questions
When should you take an energy gel?
Between 30 and 45 minutes after starting the activity, then every 30 to 40 minutes.
How many gels during a marathon?
Approximately 5 to 6, depending on your pace and digestive tolerance.
Can you take a gel without drinking?
No. Always consume it with a few sips of water.
What is the difference between a gel and an energy drink?
The gel provides concentrated energy; the drink hydrates and replenishes electrolytes.
Does an energy gel cause weight gain?
No, it simply replaces the energy expended during exercise.
Why do some gels contain caffeine?
To stimulate the nervous system and improve concentration over long distances or during nighttime events.
