How Do Energy Gels Work? | Fuel For Hard Efforts

When you’re an hour or more into a hard workout, your body’s stored fuel starts running low. An energy gel is a concentrated package of carbohydrate — commonly from maltodextrin and fructose — designed to be absorbed quickly and put that fuel back into circulation while you keep moving. The goal isn’t comfort or taste; it’s keeping your engine running when your tanks are nearly empty. For adults pushing through endurance efforts, a gel can be the difference between finishing strong and hitting a wall.

What Exactly Is Inside A Gel?

Energy gels are mostly carbohydrate, plain and simple. The sugars are usually a blend of maltodextrin and fructose, chosen because your body can absorb them through different pathways at the same time. That combination lets you take in more carbs per hour than a single sugar source would allow, which matters the longer you go.

They aren’t a general snack. The Cleveland Clinic notes that energy gels are intended for adults doing longer, harder exercise — not for everyday eating, and not for kids. The dense sugar dose is deliberate: it’s formulated to be used during effort, not as a candy replacement.

Why Timing And Water Matter So Much

A gel only works well if it’s handled correctly. The most common mistake is taking one without water. Gels are concentrated, and without fluid to dilute them, they sit heavy in the stomach and can cause real gastrointestinal distress. The Australian Institute of Sport’s guidance is straightforward: gels should be consumed with adequate fluid — water or another dilute drink — to improve tolerance and reduce gut upset.

Timing is the second half of the equation. A common guideline is one gel every 20 to 30 minutes during efforts lasting longer than an hour. But here’s what almost nobody does until they learn it the hard way: you have to practice this before race day. “Gut training” is the term sports nutritionists use — taking gels during training runs so your stomach adapts to processing them mid-effort. A gel you’ve never tested on a long workout is a gamble you don’t want to take at mile 18.

What Happens When You Get It Wrong?

The main downsides come from overdoing it or using gels wrong:

• Skipping the water — leads to nausea and that dreaded sloshy, sick stomach.
• Using them for short or easy sessions — those efforts don’t drain glycogen enough to need the boost.
• Ignoring your teeth — frequent sugary and acidic exposure can erode enamel. The advice is to minimize contact with teeth, rinse your mouth with water after, and wait at least 30 minutes before brushing.

There’s one more group that needs to read labels carefully: people with fructose malabsorption or FODMAP intolerance should pay close attention to gels containing fructose or multiple transportable carbohydrates. For everyone else, gels taken with water during moderate-intensity exercise are well tolerated by most athletes, with recent research showing similar carbohydrate delivery and muscle oxidation patterns compared with sports drinks.

Are They Right For Your Next Race?

If you’re doing endurance work of about an hour or more, gels are a legitimate, proven tool. If you’re new to them, test them on a long training day first and see whether your stomach agrees.

Your tolerance is as individual as your pace, so when you find one that works, stick with it. If you’re deciding which product to try for an event like a HYROX race, where consistent fueling across running and functional stations is critical, check our tested picks in this roundup of the best energy gels for HYROX. The right gel, taken with fluid and practiced in advance, is one of the simplest ways to keep your legs turning over when everything in you wants to stop.