Dean Karnazes, author of the book “Ultramarathon Man,” liked to joke that an ultramarathon is an eating contest with a bit of running between meals.

Welcome to the fourth discipline of the ultramarathon — eating! Yes, you heard that right. The ability to fuel properly on course is just as important as how well trained your legs are. You can be 100% ready, but if you “run out of gas” or your “fuel delivery system breaks down” (hello, GI problems!), your race will be over before it has really begun.

7.1. “Loading” Before the Start: Eat Pasta Like a True Italian!

For the 2–3 days before the start, your main task is to “fill” your glycogen depots in the muscles and liver to the brim. This is called “carb loading.” Forget the salads and the chicken breast. Your menu is pasta, white rice, potatoes, bananas.

The goal: eat 8–10 grams of carbohydrate for every kilogram of your body weight. For a 70 kg athlete that's 560–700 grams of carbohydrate a day! That's a lot. That's an entire pack of pasta and then some.
An important nuance: cut your intake of fiber (vegetables, whole grains) and fats to a minimum. They slow digestion and can be the cause of “surprises” on the course. Right now your job is to eat as many “empty,” easily digestible carbohydrates as possible.

Exactly how much glycogen fits into your “tanks” and how long it will last can be estimated in the carb depot calculator.

7.2. The 15-Minute Rule: Eat Before You Get Hungry

The biggest beginner's mistake is starting to eat only when you feel hungry. If you got hungry during an ultramarathon, you're already too late. You've already “caught” hypoglycemia, and climbing out of it will take time and energy.

The golden rule: start eating 15–20 minutes after the start. Yes, you don't feel like it at all. Yes, you're still full of energy. But you're not eating to satisfy hunger now — you're eating so that hunger never arrives two hours from now. Your goal is to constantly maintain an even blood sugar level, tossing small portions of carbohydrate into the “furnace.”

7.3. A “Double Espresso” for the Muscles: Glucose + Fructose

Imagine that your intestine has two “windows” for absorbing carbohydrates. One is for glucose (and its derivatives, like maltodextrin), the other for fructose. Each “window” has its own throughput — roughly 60 grams per hour for glucose and 30 grams for fructose.

If you eat gels containing only maltodextrin, you hit the 60 g/hour ceiling. Everything above that will “ferment” in your stomach, causing nausea.

But if you use fuel that contains both glucose and fructose, you open both “windows” at the same time! The classic 2:1 ratio (2 parts glucose to 1 part fructose) lets you absorb up to 90 g of carbohydrate per hour. Recent research shows that a ratio of 1:0.8 or even 1:1 can raise absorption to 100–120 g per hour, but it requires gut training and can cause discomfort in unprepared athletes.

7.4. Salt: The “Key” to Carbohydrate Absorption

And now for the secret ingredient many people forget about. Sodium — ordinary salt.

The glucose “window” (the SGLT1 transporter) works like a “pump” that “pulls” a glucose molecule into the cell only when it's paired with a sodium ion.

Put simply: no sodium — no glucose absorption.

You can eat the most expensive, most sophisticated gel there is, but if your body is short of sodium (and you lose it in large amounts through sweat), that gel will simply sit in your stomach, causing bloating and nausea. That's why salt tablets or a sports drink with sufficient sodium content are not a whim but a necessity.

7.5. Train Your Stomach!

Yes, the stomach and intestines can and must be trained too. If you drink only water in training and then try to cram 100 grams of carbohydrate per hour into yourself on race day, your GI tract will be in shock and will most likely “revolt.”

Start small: practice eating during your long training runs. First one gel per hour, then two.
Increase the dose: gradually accustom your digestive system to working under load.
Eat carbohydrates in everyday life: don't be afraid of carbs in your diet. The more of them you eat, the more active the enzymes and transporters responsible for absorbing them become.

Your stomach is just as important a “muscle” as your quadriceps. Train it!

In the next chapter we'll talk about the second crucial component of your “fuel” — water and electrolytes.