The Relationship Between Nutrition and Performance

Kovács Ferenc Soma, NCAA bronze medallist and All-American miler

 

“Oatmeal, eggs, or maybe peanut butter and jam on toast?” — a runner’s race-day breakfast can reveal surprisingly much about their character. Running is one of the few hobbies that fundamentally shapes daily life, including when and what we eat. A runner’s backpack or car glove compartment will almost always contain some kind of emergency snack, as runners typically have a very high daily caloric demand.

A well-balanced diet in both quality and quantity is the foundation of a healthy lifestyle. Beyond that, in performance sport it is especially important how we time our pre-training meals and how many calories we consume. The longer the duration of physical effort, the more essential it becomes to replenish glycogen stores that fuel movement. In other words, a 5 km road race can be completed on an empty stomach with relatively good performance, but before a long run, a carbohydrate-rich meal is clearly necessary.

Interestingly, many elite Kenyan runners train early in the morning in a fasted state to teach their bodies to operate with limited available energy. Eliud Kipchoge, for example, typically wakes up around 5:45 a.m. during his major marathon preparation blocks so that he can begin the day’s main session before 6:30. This first session is usually a fartlek, a long run, or interval training. After this demanding effort, Kipchoge continues his day with a substantial breakfast: tea with milk, homemade bread, fruit — especially bananas — and eggs. Notably, like many Kenyan athletes, he often adds about three teaspoons of sugar to his tea.

After this breakfast, the rest of his meals follow a structure similar to most athletes. He eats lunch around 1 p.m., and after the afternoon session (which typically begins at 4 p.m.), he has dinner. Kipchoge frequently consumes ugali, a staple of Kenyan cuisine similar to polenta made from cornmeal. It is often eaten with dry beef, beans, and managu — a spinach-like leafy vegetable native to Kenya, rich in fiber. He also regularly eats rice or boiled potatoes alongside ugali. Another key carbohydrate source in his diet is chapati, a flatbread of Indian origin.

At first glance, the diet of arguably the greatest marathon runner of all time — consisting largely of locally produced foods — appears quite similar to that of other endurance athletes. With one key difference: Kipchoge does not eat breakfast before his hard training sessions at all. This unconventional approach does not necessarily mean that he consumes no carbohydrates before a 40 km long run — he almost certainly uses gels during such sessions. Still, I would not recommend that anyone perform interval workouts or long runs in a fasted state.

Personally, I only complete short, easy early-morning runs of 6–8 km on an empty stomach. These runs take place in a heart rate zone of around 140–150 bpm and represent the first movement of the day before the main afternoon session. They serve two main purposes: on one hand, they safely increase weekly mileage — with low injury risk — and improve running economy; on the other, they force the body to optimize recovery, as there is no longer a full day available between sessions.

Additionally, these runs provide a great opportunity for endurance athletes preparing for long-distance events to improve fat oxidation. Since glycogen stores are depleted, the genes responsible for fat metabolism are activated, and the athlete burns a higher proportion of fat.

At the same time, another less visible but equally important adaptation occurs: mitochondrial efficiency improves. Mitochondria are the “power plants” of the cell responsible for energy production. When training under low energy availability, the body is forced to operate these systems more efficiently. Over time, not only can their number increase, but they also become capable of producing more usable energy from the same input. In practice, this means improved efficiency and the ability to sustain a given intensity for longer without a sudden drop in performance — an especially important advantage in long-distance racing.

However, it’s important to note that running for more than an hour in a fasted state is not recommended. If fasted training is done too frequently or for too long, it can lead to injuries and chronically elevated cortisol levels. For this reason, I personally include about three short (~30-minute) easy runs per week in a fasted state — mainly for logistical reasons. Digestion takes about an hour, so this allows me to avoid waking up significantly earlier just to eat before running.

Kipchoge and world-class triathlete Kristian Blummenfelt both use wearable glucose sensors attached to their triceps to monitor blood sugar levels in real time during training periods. They track these changes through mobile apps, collecting vast amounts of data over months. This allows them to precisely optimize both the timing and quantity of their nutrition for race day.

Real-time glucose monitoring also enables them to fine-tune in-session fueling. If they observe a steady drop in glucose levels, they can immediately take in an energy gel.

I can relate to this from personal experience. Previously, I never used gels during long runs, which often resulted in hitting the wall around 22.5–24 km. My legs would become extremely heavy, and the final 1–3 km felt like a struggle. Over the past two years, however, I switched to a different approach: consuming one or two gels containing 24 grams of carbohydrates (typically around 16 km and sometimes again at 22.5 km). The results have been clearly positive — I finish runs with much fresher legs, and I no longer need an hour-long nap afterward.

That said, during longer runs I still sometimes forget to fuel, especially around the 16 km mark. At that point, I usually still feel good and don’t notice fatigue, which makes it easy to delay taking a gel. That’s why I use the FuelWise feature on my Polar watch, which reminds me when to fuel. This helps ensure that I follow a structured plan rather than relying purely on feeling, and it prevents sudden late-run energy crashes.

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