How Many Carbs Do You Need to Fuel a Marathon? 16th Sep 2026 Facebook Email Print X Pinterest Most marathon runners can aim for 80–120 g of carbohydrates per hour, using glucose or maltodextrin alongside fructose. Start fuelling within 20–30 minutes and continue regularly to support energy availability and delay fatigue. Your ideal intake depends on pace, body size and gut tolerance, so test your marathon carb strategy during training. Key Takeaways Aim for 80–120g of carbohydrate per hour, from mixed sources such as maltodextrin and fructose, for better absorption. Start fuelling within 20–30 minutes and continue at regular intervals through the race. Combining two carbohydrate types uses two separate absorption pathways, increasing total intake capacity per hour. Caffeine taken in the first half of the race peaks in effect from roughly the halfway point to the finish. SiS BETA Fuel Gel uses a 1:0.8 maltodextrin-to-fructose ratio, designed for higher carb delivery with lower reported GI stress. Test the full fuelling plan products, timing, and volume in training; never introduce something new on race day. Why Does Fuelling Matter So Much in a Marathon? Fuelling is now recognised as being nearly as important to marathon performance as training itself. Well-trained runners typically carry only two to three hours of stored glycogen, and once those stores run low, pace drops sharply, a state commonly called "hitting the wall," often around the 32-kilometre mark. Consuming carbohydrate during the race maintains blood glucose, spares glycogen, and delays this fatigue. The Australian Institute of Sport publishes research-backed guidance on carbohydrate use in endurance sport for runners who want the underlying science. How Does the Body Use Energy During a Marathon? The body draws on two main fuel sources during a marathon: carbohydrate and fat. Carbohydrate is stored as glycogen in the muscles and liver and provides the fast energy needed to sustain race pace, while fat supplies slower, more sustained energy that cannot keep up with race-pace demands on its own. Because glycogen stores are limited, replacing carbohydrate during the run is what keeps pace steady into the closing kilometres. How Much Carbohydrate Should You Consume, and When Should You Start? Sports nutrition guidance recommends 80–120 grams of carbohydrate per hour during a marathon, with the exact figure depending on pace, body size, and gut tolerance. Fuelling should begin within the first 20–30 minutes of the race, before fatigue sets in, and continue at regular intervals rather than waiting for energy to drop. Hydration supports this process, since carbohydrate is absorbed more efficiently when fluid intake is adequate. Science in Sport's hydration range is built for this endurance-specific use case. Why Do Mixed Carbohydrate Sources Improve Absorption? Combining carbohydrate types increases how much fuel the gut can absorb per hour, because glucose or maltodextrin and fructose are each processed along a different intestinal pathway. Using both at once opens two absorption routes simultaneously, rather than overloading a single one, which also reduces the gastrointestinal distress that is a common reason runners abandon their fuelling plan mid-race. Sports Dietitians Australia guidance on endurance fuelling supports using multiple carbohydrate sources for this reason. Carbohydrate Approach How It Is Absorbed Practical Benefit Glucose / maltodextrin alone Single intestinal pathway Familiar, well-tolerated, but caps how much can be absorbed per hour Fructose alone A separate intestinal pathway Adds absorption capacity but is less commonly used on its own in race gels Combined, e.g. SiS BETA Fuel Gel (1:0.8 maltodextrin-to-fructose ratio) Both pathways used at once Supports higher carbohydrate delivery (toward the 120g/hour end of the range) with reportedly lower GI stress What Role Do Caffeine and Nootropics Play in Race-Day Fuelling? Caffeine is one of the most well-researched performance aids in endurance sport: it lowers perceived effort and sharpens focus, which matters most in the closing kilometres when decision-making and motivation are under pressure. Nootropics are compounds that support cognitive function, and pairing them with caffeine can extend that mental edge deeper into the race. Timing matters: a caffeine-containing gel taken in the first half of the race gives it time to absorb, so its effect peaks from roughly the halfway point to the finish. The BETA Fuel Nootropics Gel combines caffeine with nootropics in one format, while the GO Caffeine Shot delivers a smaller, targeted dose for other points in the race. How Does SiS BETA Fuel Gel Support a Marathon Fuelling Plan? SiS BETA Fuel Gel is built around dual carbohydrate transport, delivering a concentrated carbohydrate load using a 1:0.8 ratio of maltodextrin to fructose. Reported benefits include sustained energy output during marathon effort, reduced GI stress relative to single-source carbohydrate products, and a concentrated, easy-to-carry format for long-race fuelling. Science in Sport states that its Australian products are Informed Sport registered; verify the exact product and batch before use. See health, safety and TGA compliance for further information. How Should You Build and Test Your Marathon Fuelling Plan? The most important rule in marathon fuelling is that nothing new should be tried on race day. The gut adapts to processing carbohydrate during exercise through repeated exposure, often called gut training, so testing products, timing, and volume on long training runs confirms what the body tolerates well before race day. Runners should test the same products at the same intervals and effort level they plan to race at, note how the stomach responds, and refine the plan accordingly. What Are the Key Principles of a Marathon Carb Strategy? A well-executed fuelling plan is one of the most impactful things you can do for your marathon. The foundations: 80–120g of carbohydrate per hour from mixed sources, starting early, timing caffeine strategically, and practising in training. SiS BETA Fuel Gel and the BETA Fuel Nootropics Gel support this approach, delivering energy efficiently while keeping GI discomfort low. Pair your plan with solid hydration for the best foundation to run your strongest marathon. Explore the full range of energy products and recovery nutrition at Science in Sport to build your complete race-day toolkit. Fuel Your Marathon with Science in Sport Ready to put this strategy into practice? Explore the Science in Sport range designed for marathon runners and endurance athletes: Shop BETA Fuel Gels Shop the Marathon Fuel Pack Browse all Energy Gels View the BETA Fuel Nootropics Gel Questions about your fuelling plan? Explore our shipping and returns information. Frequently Asked Questions 1. How many carbs should I consume per hour during a marathon? Most runners should aim for 80–120g of carbohydrate per hour to maintain energy and support performance. The ideal amount depends on body size, pace, and digestive comfort. 2. Why should I use a mix of carbohydrate types during a race? Combining carbohydrates such as maltodextrin and fructose uses different absorption pathways, which lets the body take in more carbohydrate while reducing the risk of stomach discomfort. The BETA Fuel range is formulated on this principle. 3. When should I start fuelling during a marathon? Start fuelling within the first 20–30 minutes, before feeling tired or hungry. Regular intake through the race helps maintain steady energy. 4. Can caffeine help with marathon performance? Yes. Caffeine can reduce perceived effort and improve focus during endurance exercise. Taking it in the first half of the race gives it time to take effect when it is needed most. The BETA Fuel Nootropics Gel combines caffeine with nootropics for physical and mental support. 5. Should I practise my race-day fuelling strategy in training? Yes. Testing products, timing, and quantities during long training runs allows the gut to adapt. Avoid trying anything new on race day. 6. How does hydration fit into a marathon fuelling strategy? Adequate fluid intake supports carbohydrate absorption, while electrolytes support fluid balance and can help reduce fatigue. Pairing energy gels with an electrolyte product or hydration tablets supports this through the race. Facebook Email Print X Pinterest You can use this widget to input arbitrary HTML code into the page. Invalid HTML code may cause issues with the preview pane.