What's in it
What's actually in Science in Sport (SiS)?
Science in Sport is one of the big mainstream British fueling brands, and plenty of people reach for a SiS gel without knowing what is inside it. The short version: SiS sells two very different things under one name, and which one is right for you depends entirely on your target carbs per hour.
On the label
Straight from the published labels, checked June 2026. Verify on the current label, brands reformulate.
Science in Sport GO Isotonic Energy Gel
gel60 ml sachet
Science in Sport Beta Fuel Energy Gel
gel60 ml sachet
Science in Sport Beta Fuel 80 Drink Mix
drink-mix84 g sachet (≈500 ml)
GO Isotonic is single-source, which caps it near 60 g/h
The GO Isotonic gel is the famous "take it without water" gel, and that part is true: it is pre-diluted to roughly body concentration so it goes down easily. The catch is the carbohydrate. It is single-source maltodextrin, a glucose-type carb with no fructose. Glucose-type carbs share one gut transporter (SGLT1), which saturates around 60 g/h (Jeukendrup). So GO Isotonic is a solid pick up to about 60 g/h, but it can't efficiently carry you past that on its own.
Beta Fuel is the 1:0.8 high-rate line
Beta Fuel (the gel and the 80 drink mix) is maltodextrin plus fructose at a published 1:0.8 ratio. Adding fructose recruits a second transporter (GLUT5), which lets your gut absorb more total carbohydrate per hour. The 1:0.8 split lines up with what Hearris et al. (2022) found works at higher intakes. This is the side of the range built for 80 to 120 g/h.
Which to pick, by rate
Under about 60 g/h, the single-source GO Isotonic is fine and easy on the stomach. Above that you want the multiple-transportable 1:0.8 of Beta Fuel to actually absorb what you are taking in. Neither is "better", they are for different intensities, and the higher numbers assume a trained gut (gut training).
Make your own Science in Sport
Both are straightforward to replicate. A GO Isotonic equivalent is plain maltodextrin in water, kept near isotonic for the same easy-sipping feel. A Beta Fuel equivalent is maltodextrin plus fructose at 1:0.8, the same published split. The calculator solves the grams for your target g/h and splits them across your actual bottles or flasks, which is the annoying part by hand.
Frequently asked
Does SiS GO have fructose?
No. The GO Isotonic Energy Gel is single-source maltodextrin, a glucose-type carb, with no fructose and so no glucose:fructose ratio. That is why its useful ceiling sits around 60 g/h.
What is SiS Beta Fuel's ratio?
SiS publishes a 1:0.8 glucose:fructose ratio for the Beta Fuel gel and the Beta Fuel 80 drink mix. That maps to what research suggests for higher carb intakes (Hearris 2022).
SiS GO Isotonic or Beta Fuel?
Depends on your target. GO Isotonic (22 g, single-source) suits about 40 to 60 g/h and goes down without water. Beta Fuel (40 g gel or 80 g drink, 1:0.8) is built for higher rates, roughly 50 to 120 g/h depending on the format.
Can you make your own SiS gel?
Yes. GO Isotonic is essentially maltodextrin in water; Beta Fuel is maltodextrin plus fructose at 1:0.8. The calculator works out the grams for your rate and carriers.
Figures checked June 2026 against each brand's published label; always verify on the current label, as manufacturers reformulate. This is an independent, informational breakdown. carbsperhour is not affiliated with, endorsed by, or sponsored by Science in Sport or any brand named here, and nothing on this page is medical or nutritional advice. Science in Sport and other product names are the trademarks of their respective owners.