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Since Science in Sport (SiS) “relaunched” its Beta Fuel series, many readers have wondered how the new energy gel differs from the brand’s original Go Isotonic gel? We have tested both thoroughly in recent months, so please allow us to break it down for you.

We have continued to use the two products in races and training since publishing full reviews for SiS Beta Fuel and SiS Go Isotonic energy gels. So this piece also provides our updated takeaways – without further ado.

Nutrition facts and ingredients of SiS Go and SiS Beta Fuel energy gels

Before we get into the subjective side of things, let’s look at the numbers. Here is a side-by-side comparison of the Go and Beta Fuel series.

SiS Go

  • Water
  • Maltodextrin (from maize) (33%),
  • Gelling Agents (Gellan Gum, Xanthan Gum)
  • Natural Flavoring, Acidity Regulators (Citric Acid, Sodium Citrate)
  • Preservatives (Sodium Benzoate, Potassium Sorbate)
  • Sweetener (Acesulfame K)
  • Sodium Chloride
  • Antioxidant (Ascorbic Acid)

SiS Beta Fuel

  • Water
  • Maltodextrin (from maize) 30%
  • Fructose (23%)
  • Flavorings
  • Acidity regulators (citric acid, sodium citrate)
  • Gelling agents (Gellan Gum, Xanthan Gum)
  • Preservatives (Sodium Benzoate, Potassium Sorbate)
  • Sodium Chloride
  • 60 ml
  • 87 calories
  • Fat 0 g
  • Protein 0 g
  • Carbohydrates 22 g, of which 0.6 g are from sugar
  • Salt 0.01 g
  • 60 ml
  • 158 calories
  • Fat 0 g
  • Protein 0 g
  • Carbohydrates 40 g, of which 19 g are from sugar
  • Salt 0.03g

There are two main differences between the energy gels:

  1. It’s their caloric and carbohydrate content. Beta Fuel delivers a blistering 158 calories and 40 g of carbohydrates compared with Go’s 87 calories and 22 g of carbohydrates (interestingly, only 0.6 g are from sugar). Go’s primary source of carbohydrates is maltodextrin, and Beta Fuel includes both maltodextrin and fructose in a 1:0.8 glucose-to-fructose ratio.
  2. Go is an isotonic energy gel, and Beta Fuel isn’t. An Isotonic gel means that it has the same concentration as cells inside your body; therefore, no osmotic movement of water is required when processing the gel. SiS’s isotonic formula “allows the gels to empty from the stomach quickly as no fluid needs to be drawn into your stomach to dilute the gel, providing fast energy.” The company claims that you can take the gels without a fluid chaser, reducing the risk of stomach bloating from over-drinking.

Flavor and consistency of SiS Go and SiS Beta Fuel

Both energy gels taste fine, more than palatable. Due to its higher sugar content, Beta Fuel has a thicker texture.

With its higher water content and isotonic property, the Go series is light and milder in sweetness.

Go comes in nine flavors compared to Beta Fuel’s two. We’ve tried them all. We pick Lemon Lime as the top flavor for Go and Orange for Beta Fuel.

In the flavor and consistency category, Go gets the edge.

Packaging of SiS Go and SiS Beta Fuel

Their packaging is the same size at 16 cm x 4.5 cm. SiS Beta Fuel is a hair shorter, but not enough to make a difference in how you would carry the energy gels. They also have the same opening design, which rips easily for a smooth consumption experience.

When I tested them separately before, I mistakenly thought the wrapper material for Beat Fuel was thicker. After comparing them side by side, they feel the same by touch.


So who should use which one?

The rule of thumb is to consume 1 g of carbohydrates per kg of body weight per hour, meaning a 70 kg athlete should take in 70 g of carbohydrates hourly. Recent studies have further shown that the human body can absorb up to 90-120 g of carbohydrates per hour for maximum athletic performance. However, it’s not so straightforward in practice.

Energy gels are essentially concentrated sugar water, which is something you don’t usually put in your digestive system. Too much carbohydrates and sugar too fast can overwhelm your stomach, causing gastrointestinal distress when you need to perform athletically. Here’s everything you need to know on how energy gels might cause an upset stomach.

Just like your legs, heart, and lungs, your stomach also requires training to perform.

SiS Go, with its isotonic property and lower carbohydrate content, is designed to be stomach-friendly. This is a better option if you’re new to running and fueling with energy gels or have a sensitive stomach.

SiS Beta Fuel has a whoppin’ 40 g of carbohydrates per energy gel. That’s a lot! It’s created to keep athletes fully and rapidly topped up. If your stomach is well acclimated to the hefty dosage of sugars, Beta Fuel is the super fuel to energize you.

Remember, just because the latest studies say that you can eat 120 g of carbohydrates per hour, it doesn’t mean you have the ability to do it immediately. It takes “practice” to build up a tolerance over time.

How did the energy gels perform? Which one is faster reacting?

The mouth-to-muscle time for Beta Fuel is simply superior. Given its much higher sugar content, a significant spike in blood sugar level is not surprising. However, what goes up must come down. Blood sugar peaks and troughs can be detrimental to performance.

Go, on the other hand, provides a “steadier” experience. I never get that “boosted” feeling, which I used to think was a negative. But I have since learned to appreciate sports nutrition that doesn’t spike my blood sugar level.

Here’s our recommendation. If it’s an easy-to-moderate session where you want to maintain a consistent effort, go with SiS Go. For runs where you will change paces to surge, before tackling a big climb or getting ready to finish strong, Beta Fuel will give you that extra rocket boost.

Carrying convenience and consumption tips

The packaging of the SiS energy gels is huge. Be sure they fit in your fuel-carrying gears, such as shorts pockets and various compartments of your hydration vests and packs.

At 60 ml, Go doesn’t provide a lot of calories and carbohydrates, meaning you have to carry more sachets and weight to get the same amount of fuel. Beta Fuel, on the other hand, is energy packed. Consume two Beta Fuel gels and you’ve banked 300+ calories and 80 g of carbohydrates.

When you’re running hard and exhausted, the fewer energy gels you have to carry and the fewer times you have to fiddle around your running belt or hydration pack for an energy gel and open it, the better.

60 ml is a lot of syrupy concoction to take in all at once. Here’s a tip: Open the energy gel and take a sip (a quarter or a third). Run with the partially consumed pack briefly before taking the next sip. Consumer the entire gel over 2-5 minutes to avoid stressing your digestive system.

The verdict

If your digestive system is well-trained and you’re going on a long run over two hours, SiS Beta Fuel is the energy gel of choice. It provides more calories and carbohydrates per gel, meaning you can carry less on these extended efforts. It also contains a blend of glucose and fructose, which research studies have proven to be more effective in replenishing glycogen stores.

However, if your stomach is on the sensitive side or you’re going on a shorter run and prefer not to carry a water bottle, SiS Go Isotonic is just the sports fuel for you. One drawback is the subpar volume-to-carbohydrate ratio. If you use Go on long runs and rides, you will need to bring more gels and consume a higher volume.

Regarding taste and texture, the Go series is pleasantly light. We find it ideal for runs in higher temperatures. Go also offers a broader selection of flavors. Both energy gels are more than palatable, two of the “tastier” ones we’ve tested.