Are SiS Gels Easy to Digest? Unpacking the Isotonic Formula

November 12, 2025 •

4 min read

According to Science in Sport, their GO Isotonic Energy Gel was the world's first isotonic gel, designed to be easily digestible. Many athletes report experiencing digestive distress from energy gels, but SiS's isotonic formula is engineered to reduce this common issue, making SiS gels easy to digest and a reliable fuel source during exercise.

Quick Summary

SiS gels are formulated to be easy on the stomach, primarily due to their isotonic properties and use of maltodextrin. Their liquid consistency and specific carbohydrate blend facilitate quick absorption without causing the bloating and discomfort often associated with hypertonic gels. This makes them a reliable fueling option for endurance athletes, especially those with sensitive digestive systems.

Key Points

Isotonic Formula: SiS gels have a concentration similar to body fluids, allowing for rapid absorption without needing extra water and minimizing stomach discomfort.
Maltodextrin-Based: The primary carbohydrate is maltodextrin, which provides quick energy without the osmotic stress or high sweetness of simple sugars that can trigger GI upset.
Less Bloating: Because the isotonic formula doesn't pull water from your body to dilute it, it helps prevent the bloating and cramps common with hypertonic gels.
Water-Free Consumption: The design allows for consumption without extra water, simplifying fueling during high-intensity exercise when drinking is difficult.
Requires Practice: As with any fueling, gut training and proper timing are essential to maximize tolerance and performance, even with an easily digestible gel.

The Science Behind SiS Gels and Easy Digestion

When you're pushing your limits in an endurance sport, the last thing you want is a GI upset. Bloating, cramping, and nausea can sideline your performance faster than any fatigue. SiS gels, particularly the GO Isotonic Energy Gel, have built a reputation for their digestibility. The key to their stomach-friendly nature lies in their isotonic formula and carefully selected carbohydrate source.

What does Isotonic mean?

The term 'isotonic' refers to a solution's concentration of dissolved particles compared to the fluid in your body's cells. An isotonic solution, having a similar concentration to your body's fluids, can be absorbed directly by the gut without requiring extra water to dilute it. In contrast, a hypertonic solution (like many traditional, thicker energy gels) has a higher concentration, forcing your body to pull water from your cells into the gut to aid digestion. This process can lead to dehydration, bloating, and stomach cramps during exercise, when blood is already being diverted away from the digestive system to working muscles. By being truly isotonic, SiS gels bypass this issue, allowing for faster absorption and less gastric distress.

The Role of Maltodextrin

The primary carbohydrate in SiS gels is maltodextrin, derived from corn. Unlike simple sugars such as fructose or sucrose, maltodextrin has a high molecular weight and is minimally sweet. While it breaks down quickly into glucose for energy, it doesn't cause the same osmotic effect as concentrated simple sugars. A high intake of simple sugars can overwhelm the small intestine, leading to fermentation in the large intestine and subsequent gas, bloating, and discomfort. By using maltodextrin as the main carbohydrate source, SiS minimizes the risk of these issues.

Training Your Gut and Fueling Strategy

Even with an easily digestible gel like SiS, proper fueling technique is crucial to avoid stomach problems. Your gut is trainable, and consistently practicing your nutrition strategy during training can significantly improve tolerance on race day.

Best practices for using SiS gels:

Start with a training session: Never try a new fueling product for the first time during a race. Test SiS gels on your longer training runs or rides to see how your body reacts.
Stay hydrated: While SiS gels don't require extra water for digestion, maintaining overall hydration is essential for performance and gut function.
Fuel consistently: Rather than taking multiple gels at once, consume them regularly over the course of your exercise. Science in Sport recommends 1-3 gels per hour depending on your sport and intensity, to achieve a 60g-90g target intake.
Know your body: Pay attention to your body's signals. If you have a sensitive stomach, consider taking smaller amounts more frequently.

Comparison of SiS GO Isotonic vs. Other Gels


Feature	SiS GO Isotonic Energy Gel	Traditional Hypertonic Gels	SiS Beta Fuel (Hypertonic)
Tonicity	Isotonic (same concentration as body fluid)	Hypertonic (higher concentration)	Hypertonic
Water Needed?	Not required for digestion, though good for hydration	Required to be consumed with water	Requires fluid intake
Digestion Speed	Rapid gastric emptying	Delayed gastric emptying	Can be very fast if gut-trained
Bloating Risk	Minimizes risk of bloating	Higher risk of bloating and discomfort	Risk reduced with gut training
Primary Carb Source	Maltodextrin only	Often simple sugars like fructose	Maltodextrin and Fructose (1:0.8 ratio)
Flavor/Texture	Watery and mild	Thicker, often very sweet	Thicker due to higher carb content

Beyond the Isotonic Formula: Other Factors

While the isotonic formula is the main reason SiS gels are easy to digest, other factors contribute to their overall gut-friendly profile. The use of clean ingredients and the absence of certain additives can make a significant difference for sensitive individuals.

For example, some energy gels contain artificial sweeteners or sugar alcohols, which are known to cause gastrointestinal issues in some people. SiS gels generally avoid these, sticking to natural flavorings. Additionally, for those sensitive to caffeine, SiS offers a range of caffeine-free gels, as caffeine can increase gut motility and exacerbate stomach problems during intense exercise. By offering these options, SiS provides athletes with more control over what they put into their bodies, further reducing the risk of digestive issues.

Conclusion

For endurance athletes concerned about stomach discomfort, the question "are SiS gels easy to digest?" has a clear answer: yes, they are, especially when compared to many conventional energy gels. The foundational science behind their GO Isotonic gels—using an isotonic formula with maltodextrin as the carbohydrate source—allows for rapid and efficient energy absorption with minimal gastric distress. By understanding the 'why' behind their design and combining it with smart fueling practices, athletes can confidently rely on SiS gels to power their performance without worrying about mid-race stomach problems.

This article is for informational purposes only and is not a substitute for professional medical or nutritional advice. Consult with a healthcare professional or sports nutritionist before changing your diet or supplement routine.

Frequently Asked Questions

An isotonic gel has a concentration of dissolved particles similar to your body's fluids. This means your body doesn't need to draw extra water from your cells to digest it, leading to faster absorption and a significantly reduced risk of stomach upset like bloating or cramping.

No, SiS GO Isotonic gels are designed to be consumed without water. The isotonic formula means the gel can be digested efficiently on its own, though you should still maintain overall hydration with regular fluid intake.

While SiS gels are generally easy to digest, some individual sensitivity is possible. Stomach problems are less likely than with conventional gels, but proper fueling strategy and testing during training are always recommended.

SiS GO Isotonic is a lighter, maltodextrin-based gel, while SiS Beta Fuel is hypertonic and contains a maltodextrin-fructose blend for higher carbohydrate delivery. Beta Fuel is best for trained guts and longer efforts, while GO Isotonic is gentler, especially for new athletes or those with sensitive stomachs.

Many gels are hypertonic, meaning they have a high concentration of carbohydrates. To process this, your body pulls water into the gut, which can cause bloating, cramps, and discomfort, especially when blood is already diverted to your muscles.

Yes, SiS GO Isotonic gels are often recommended for beginners or athletes with sensitive digestive systems because of their easy-to-digest formula. They provide a good entry point for practicing fueling during exercise.

SiS gels use natural flavorings and avoid many of the artificial sweeteners or sugar alcohols that can cause digestive issues. Checking the specific product ingredients is always a good practice.