Many endurance athletes think about what to eat but pay less attention to when to eat it. Yet timing can be the difference between finishing strongly and spending the final hour simply trying to survive.
Your body stores carbohydrates mainly as glycogen in the muscles and liver. These stores are limited. During a longer or harder session, you gradually use them—and once they become too low, maintaining the same intensity becomes increasingly difficult.
This is why fueling should not begin when you already feel exhausted.
Fueling is prevention, not rescue
Feeling hungry, losing concentration or noticing a sudden drop in power are often late signals. By that point, eating a gel may help, but it cannot immediately reverse the situation. The carbohydrates still need to be digested, absorbed and transported to the working muscles.
A better approach is to start early and continue regularly. Instead of waiting for a crisis, you supply manageable amounts of carbohydrate throughout the session.
Think of it like keeping a fire burning: adding small pieces of wood regularly works better than waiting until the fire is almost out.
What elite athletes can teach us
A recent Helsingin Sanomat article looked at the widespread use of energy gels in endurance sport. Rower, doctor and researcher Joel Naukkarinen explained that the benefits of consuming carbohydrates during endurance exercise are clear. He also highlighted why gels are so practical: they provide concentrated energy and are generally easier to consume and digest during exercise than normal food.
The article uses European marathon champion Alisa Vainio as a visible example. During her championship-winning run, she repeatedly collected both drinks and gels from the aid stations. The important lesson is not simply that an elite athlete used gels—it is that fueling was planned and repeated throughout the race, rather than left until fatigue appeared. Read the HS article.
More carbohydrate can change how the same effort feels
The Running Channel explored underfueling in a laboratory test at Loughborough University. Two runners completed tests using very different strategies: approximately 20 grams versus 80 grams of carbohydrate per hour. The experiment examined carbohydrate use, perceived effort and performance—not only how much carbohydrate the athletes consumed.
The video offers a useful reminder: two sessions with the same duration and intensity can feel very different depending on how well the athlete is fueled.
This does not mean that everyone should immediately consume 80 grams per hour. Fueling requirements depend on session duration, intensity, sport, experience and individual tolerance. Higher carbohydrate intake also needs to be practised progressively during training. Whatch the video.
A simple approach for your next long session
Before starting, estimate how long and demanding the session will be, then determine approximately how much carbohydrate you need, which foods, drinks, or gels you will use, when you will consume each serving, and whether the plan is comfortable for your stomach.
For longer or performance-focused sessions, start fueling before you feel hungry—often within the first 30–45 minutes—and continue at regular intervals. Drinks can provide carbohydrates continuously, while gels and solid foods can be placed at specific moments.
The best fuel is not necessarily the product with the biggest number on the label. It is the fuel you can tolerate, carry and consume at the right time.
That is the idea behind Fuel Snapshot: turn a carbohydrate target into a practical timeline you can follow while running, riding or training. Because knowing what to eat is useful—but knowing when to eat it is what makes the plan work.