As athletes continue to push the limits of human performance, the methods of fueling for endurance events have evolved significantly. Energy gels have become a popular choice among marathon runners, offering a convenient and concentrated source of carbohydrates. This article explores the science behind energy gels, their effectiveness, and considerations for their use during endurance activities.
Sebastian Sawe tore open a carbohydrate gel sachet and consumed it five minutes before the start of the 2026 London Marathon. An hour later, he took another one, ultimately shattering the two-hour barrier for marathon finishing times.
While Sawe made history as potentially the first sub-two-hour marathon runner, he certainly isn’t the first athlete to rely on energy gels for performance enhancement. Evidence suggests that over 70% of marathon runners utilize gels in their training and races.
Long before the invention of energy gels, endurance athletes relied on a variety of foods to fuel their activities. These foods ranged from sugar cubes and coffee to chocolate, beer, wine, and even egg whites and brandy.
However, by the 1970s, scientific research began to catch up with these practices. Studies indicated that carbohydrates serve as effective fuel for extended endurance activities, particularly those containing glucose and fructose.
Thanks to decades of investigation, today’s athletes can choose energy gels, which provide precisely formulated carbohydrates in blends of maltodextrin and fructose, enclosed in a hydrogel.
Despite the technological advancements and promises of enhanced energy and performance, some scientists remain skeptical about the true efficacy of these gels. Additionally, many athletes experience uncomfortable side effects.
This raises the question: are energy gels genuinely worth the investment, or should athletes revert to more traditional, albeit less flashy, food sources for fuel?
Fueling with Energy Gels
When consuming food, our bodies gradually break down carbohydrates in the stomach, transforming them into glucose (a simple sugar) in the bloodstream.
This glucose is then transported to the muscles and liver, where it gets stored as glycogen. This storage allows the body to quickly access energy when necessary.
However, our glycogen reserves typically last approximately 90 minutes before they are depleted. Once these reserves are exhausted, performance can suffer. Therefore, many endurance athletes consume carbohydrates during lengthy races and training sessions to avoid running out of fuel.
In practical terms, energy gels offer a rapid, convenient, and concentrated source of carbohydrates that can be consumed during a race without needing to slow down. Compared to whole foods, they are easier to digest and offer more precise dosing, aiding runners in maintaining a steady energy level.
However, this convenience has its drawbacks: gels can be costly, may not appeal to all athletes, and are often linked to gastrointestinal discomfort—especially if consumed in large quantities or without enough water.
Simpler alternatives such as sports drinks or sugary snacks can provide similar energy levels but usually lack the portability and accuracy that gels offer.
Moreover, studies have shown considerable variation among products available on the market. A review of 31 different gel brands (totaling 51 flavors) revealed significant differences in serving sizes, carbohydrate content, sugar levels, and even osmolality (the concentration of solutions), which can affect how and when gels should be consumed and the physiological responses they generate.
Moreover, gels may not provide any added advantages over other sources, like sports drinks.
A 2010 study indicated that gels and beverages deliver carbohydrates to muscles at similar rates. This was further supported by a 2022 study demonstrating no significant differences in the benefits received from drinks, gels, or chews.
The primary advantage of gels lies in their convenience; they can easily be stored and consumed mid-run.
Nevertheless, gels may come with some downsides. Gastrointestinal issues are commonly reported, affecting around 10-20% of users, according to one study.
Hydrogel drinks and products are designed to form gels in the stomach, aimed at minimizing water absorption across the intestinal barrier to prevent bloating and cramps. This method is thought to facilitate more effective carbohydrate transport into the bloodstream.
However, research has not consistently shown improved performance or reduced gastrointestinal distress compared with traditional carbohydrates, even when calories are matched.
The concentrated nature of gels leads them to reach the small intestine quickly, where their sugar concentration is often higher than that of surrounding blood and tissue. As a result, water may be drawn into the gut, contributing to bloating and cramps if not paired with adequate hydration.
How to Use Gels Effectively
If your run lasts less than 60 minutes, you likely won’t need gels.
For runs ranging from 60 to 90 minutes or longer, it’s crucial to fuel before you feel depleted. Aim for approximately 30-60g of carbohydrates per hour.
Even if you don’t feel hungry, taking small, regular amounts of carbohydrates—such as a few sips or half a gel every 15-20 minutes—can help sustain energy levels before fatigue sets in.
For long races, strive for about 60-90g of carbohydrates per hour. A blend of glucose and fructose is often most effective during high-intensity efforts.
The key takeaway is to practice with gels during training sessions. Don’t wait for race day to try them for the first time; this way, you can determine if they suit your body and enhance your performance.
Related: Think Your Metabolism Runs Fast? The Science May Surprise You
A small number of runners are particularly susceptible to gastrointestinal issues. If this applies to you, switching brands might help alleviate the problem.
However, if gels consistently cause you trouble, consider reverting to older techniques. Foods such as bread, fruit, sugar lumps, bananas, dates, and rice cakes were once staples for endurance athletes before gels emerged.
It’s vital to practice using these foods during training as well to gauge how well they work for your body.
While these foods are effective at lower intensities, gels have remained popular thanks to their consistent dosing and convenience for quick consumption.
Alan Ruddock, Associate Professor of Sport Physiology and Performance, Sheffield Hallam University and Mayur Ranchordas, Professor of Applied Sport Nutrition and Sport Nutrition Consultant, Sheffield Hallam University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
