Walk any marathon finish line and you’ll see them: hundreds of sad, sticky rectangles decorating the asphalt like fallen soldiers of fructose. Energy gels, those gooey, neon-packet shots of “rocket fuel”, are both the saviour and the punchline of endurance sport. They’re a large part of the reason half the field finishes upright, while the other half spends mile 22 negotiating with their intestines.
If you’ve ever wondered why anyone would voluntarily slurp down something that tastes like liquefied cough syrup mid-run, congratulations, you’re human. But underneath that sticky shell sits a carefully engineered carb-delivery system doing real metabolic work.
The Science Behind the Slime
When you run, cycle, or otherwise engage in self-inflicted cardio suffering, your muscles rely on two main fuel sources: fat and carbohydrates. Fat is like that friend who’s always late; dependable, energy-dense, but slow to arrive. Carbs, on the other hand, are the punctual overachievers of metabolism. They break down into glucose, which your body’s aerobic machinery converts into ATP, the biochemical currency that keeps you moving forward and not face-planting at kilometre 35.
The catch? Your glycogen (stored carbohydrate) supply is finite. After about 90 minutes of sustained effort, those reserves start running on fumes. Without backup fuel, you’ll meet the endurance athlete’s boogeyman: the bonk — a charming mix of fatigue, brain fog, and existential dread. Enter the gel: roughly 25 grams of quick-release carbs, engineered to be absorbed fast enough to rescue your plummeting blood sugar before your quads stage a revolt. The “gel” part comes from thickening agents like maltodextrin, pectin, or xanthan gum, which create a viscous matrix that slows spillage in your hand but not absorption in your gut.
But Wait, Are All Gels Created Equal?
Ah, if only. A 2024 study in the International Journal of Sport Nutrition and Exercise Metabolism tested eight popular energy gels and found that several contained less carbohydrate and energy than advertised on the nutrition label, with one product (Spring Energy’s Awesome Sauce) standing out for its shortfall. Conducted at an independent FDA-accredited lab, the analysis revealed a systematic bias toward underreporting carbs, a finding that Canadian Running later spotlighted with concern. While most gels technically stayed within the 15% leeway allowed by federal labeling regulations, it’s important to note that “technically legal” doesn’t necessarily mean “accurate” in this context. When you’re calculating race fuel to the gram, that missing glucose can be the difference between cruising through the final miles and crying into a space blanket at the finish line.
So yes, the general advice still stands: aim for 30–60 grams of carbohydrate per hour, or up to 90 g/hr for efforts longer than two and a half hours. But remember, those numbers only work if your gel label is accurate. If it’s not, you could end up under-fueled, over-bonking, and wondering why you just paid four dollars for a pouch of false promises and sticky fingers.
Meet the Gels
- Classic gels: dense and sweet, designed for quick energy but best taken with a sip of water to help with absorption and prevent that “mouth-glued-shut” feeling
- Isotonic gels: lighter and pre-diluted, making them easier to digest and a good option when you want carbs and hydration in one go
- Caffeinated gels: for when you need both a physical and mental boost — a mix of glucose and just enough caffeine to keep your focus sharp
- Natural/organic gels: often made from fruit purées and simpler ingredients, popular with athletes who prefer a gentler option or have sensitive stomachs
Pick your poison, or rather, your glucose delivery system. The key is to test them before race day. Your gut has opinions, and it doesn’t like surprises.
The Alternatives
Hate gels? Join the club. You can get a similar carb hit from energy chews, candy, dried fruit, or even maple syrup packets. Most of these options are cheaper, tastier, and won’t leave you wondering when food stopped tasting like, well, food. Just make sure they’re easy to carry and digest, and that you’re still hitting that magic 30-60 g/hr sweet spot.
The Final Verdict
If you’re serious about performance, or just really hate the feeling of running out of gas mid-race, gels still reign supreme for convenience and precision. But if you’re a runner going off vibes and chasing endorphins, not podiums, the alternatives will do just fine.
Ultimately, the best gel is the one that doesn’t send you sprinting to the nearest porta-potty. Try a few, mix and match, and don’t be afraid to look ridiculous experimenting — it’s basically a rite of passage in endurance culture.
So, whether you’re fuelling with gels, gummies, or sheer stubbornness, remember: the body runs on science, not suffering. Take the gel before you need it, thank your mitochondria for their service, and for the love of glycogen, don’t wait until the bonk!
Sophie Tseng Pellar recently graduated from McGill University with a Bachelor of Science (BSc) degree in the physiology program. She will be continuing her graduate studies in the surgical and interventional sciences program at McGill. Her research interests include exercise physiology, biomechanics and sports nutrition.
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