The 2026 London Marathon saw two athletes break the 2-hour marathon barrier. Sabastian Sawe set the world record with 1:59:30 and Yomif Kejelcha came in at 1:59:41. In third place was Jacob Kiplimo with a time of 2:00:28.
According to post-race reports, the athletes consumed these amounts of carbohydrates:
- Sawe: 115 g/h
- Yomif Kejelcha: 70 g/h
- Jacob Kiplimo: 123 g/h
While you might never even dream of performing at this level, there is still a lot we can learn about marathon fueling by looking at the fueling strategies these elite athletes used to achieve 2-hour marathon times.
Dr. Tim Podlogar and Alex Rhodes discuss these strategies in detail in the Nduranz podcast. Listen here, or keep reading for the key insights.
The Energy Demands of a 2-Hour Marathon
Sawe’s splits were around 14 minutes per 5 km for most of the race. Towards the end, his pace accelerated with the 35k split coming in at 13:54 and 40k split at 13:42.
Dr. Podlogar estimates that the top three athletes have a VO2 max of around 80 milliliters per kilogram, per minute, which is roughly double that of moderately-trained athletes.
The higher the VO2 max, the greater the oxygen uptake capacity, and therefore the higher the potential energy turnover.
This translates to extremely high carbohydrate demands: approximately 5 grams of carbohydrates per minute. For a 2-hour marathon, that’s roughly 600 grams of carbohydrates, or ~2400 kcal.
Pro Fact: The cycling equivalent of a 2-hour marathon would be sustaining around 6 watts per kg for two hours.
The Role of Fueling in a 2-Hour Marathon
Whether an athlete is running a 2-hour or a 4-hour marathon, fueling with rapidly-absorbing carbohydrates is essential to meet energy demands. Without carbohydrate intake, marathon runners would quickly deplete limited liver glycogen stores, causing a drop in blood sugar and the inevitable bonk.
However, Dr. Podlogar notes that it isn’t liver glycogen that ultimately determines marathon performance. It’s muscle glycogen.
Even with proper carb loading to ensure muscle glycogen stores are full on race day, the muscles simply don’t hold enough glycogen to cover the full energy demands of marathon.
Research shows that even high carbohydrate intake does not fully spare muscle glycogen. At the intensity required for a 2-hour marathon, muscle glycogen would become critically low. Because of this, Dr. Podlogar believes the record-breaking runners are also oxidizing some fat for energy.
High Intake Improves Running Economy
This is where the physiology gets really interesting: fat is a less efficient fuel source than carbohydrates. When every second counts, suppressing fat oxidation in favor of carbohydrates can improve running performance.
High carbohydrate intake can shift your body to oxidize more glycogen and less fat. Research shows that fueling with amounts of 60 g/h already improves running economy.
Based on this, some research prior to the 2026 London Marathon suggested that athletes would need at least 110 g/h to break the 2-hour marathon barrier.
Yet, we’ve clearly seen that it’s possible with just 70 g/h.
The Importance of Gut Training
If he were tasked to create a fueling plan for a 2-hour marathon, Dr. Podlogar says he would prescribe at least 100 g/h.
However, he’s also quick to note that high carb intake only improves performance if the athlete can handle those amounts.
Because of the high-impact movement of running, marathoners are highly susceptible to GI distress. Gut training is key to ensure adequate carbohydrate intake. This involves gradually increasing carbohydrate intake and fluid consumption during training to ensure gut comfort. Read more in our Guide to Gut Training.
We don’t know why Kejelcha’s fueling strategy was lower. Dr. Podlogar suggests he may not have been fully gut trained like Sawe and Kiplimo. Research is still limited, so it’s unclear whether higher intake would have improved Kejelcha’s performance.
Implications of Two Missed Bottles
Kejelcha actually planned to fuel with 80 g/h, but he missed two bottles containing a combined 19 g of carbohydrates. After the race, he immediately apologized to his nutritionist for deviating from the plan, and said he felt “empty” towards the end.
Given what we know about elite-level marathon fueling, Dr. Podlogar notes that 80 g/h is still on the low side. However, considering carbohydrate oxidation rates, he thinks the extra 19 grams of carbohydrates wouldn't have made a significant difference in the outcome of the race.
Rather, he suggests that those missed bottles had a psychological effect: The mistake could have caused Kejelcha to get out of rhythm and lose focus, which could have affected performance.
What Changes in a 3+ Hour Marathon?
Elite marathoners have far better running economy than amateurs, meaning they use less energy per kilometer.
Because of this, amateurs may actually have slightly higher total energy costs – but the difference is small. In practice, the overall energy demand of a marathon is similar whether it is completed in 2 hours or in 3–4 hours.
The real difference is time.
This affects hourly fueling requirements, GI risk, and muscle glycogen stores.
Amateurs Have Lower Hourly Fueling Requirements
Elite runners compress the same total energy expenditure into a much shorter window, which drives a far higher energy requirement per hour.
By contrast, athletes running for 3 hours or more have more time to meet those demands, allowing them to rely on lower hourly intake.
Increased Risk of GI Issues
Current guidelines say that the gut can absorb up to 90 grams of carbohydrates per hour as glucose and fructose. Ideally, the carbohydrates should be in a 1:0.8 ratio, which is what Nduranz uses across all energy gels and energy drinks.
However, this is not a fixed number: some athletes absorb much less where as others absorb more.
When intake exceeds absorption, carbohydrates accumulate in the gut. This leads to GI symptoms, such as bloating or a sudden urge to go to the bathroom. These GI issues are common reasons for DNFs in marathons.
With a 2-hour marathon, there is limited time for this accumulation to become problematic.
For example, consider an athlete consuming 120 g/h but only absorbing 90 g/h. Each hour would leave 30 g/h undigested in the gut.
- Over a 2-hour race, the athlete would finish with 60 g of undigested carbohydrates accumulated in the gut. Most of the race would be spent with a tolerable amount of undigested carbs.
- Over a 3-hour race, the athlete would accumulate 90 grams, increasing the likelihood of GI distress.
Accelerated Glycogen Use
Further, as we talked about in our article on fueling with over 90 g/h, high intake doesn’t just suppress fat oxidation. It can also accelerate muscle glycogen use.
For a 2-hour marathon, this could further improve running economy. However, beyond 2-hours, the faster muscle glycogen could lead to earlier fatigue. This is one reason why fueling with high amounts is not recommended, particularly for events lasting over 2 hours.
The Takeaway: 80 g/h Is a Practical Target for Most Marathoners
Dr. Podlogar says that 80 g/h is the sweet spot for most marathoners attempting a 2- to 3-hour marathon time.
This amount spares glycogen and improves running economy, but without the risk of accelerated muscle glycogen use. It also reduces the risk of GI distress from undigested carbohydrates.