How to Fuel for Long Runs

For runs under 60 to 75 minutes, your glycogen stores are sufficient and you do not need to eat mid-run. Once you go past 75 minutes — which covers most long runs in a half-marathon or marathon plan — taking in carbohydrates will keep your energy level stable and your pace honest.

The common mistake is waiting until you feel hungry or tired. By that point, glycogen is already low and catching up is slow. Start fueling at around 45 minutes into the run, before your stores dip.

The guideline most sports dietitians use is 30 to 60 grams of carbohydrate per hour of running, and up to 90 grams per hour for efforts lasting well over two hours when you mix carbohydrate types (glucose plus fructose). Most energy gels contain 20 to 25 grams, so taking one every 30 to 45 minutes falls in the right range.

Your stomach also has to be trained to absorb fuel while running. Start with smaller amounts on shorter long runs and build up, exactly the way you build mileage.

Gels are the most convenient option: light, fast-absorbing, and easy to carry. Chews work similarly and suit runners who prefer something to bite into. Real food — small pieces of banana, dates, rice balls, or boiled potatoes — is a legitimate alternative and worth testing if gels upset your stomach.

Sports drinks can double as hydration and carbohydrate at the same time. If you use them on the run, adjust your gel intake so you are not doubling up and overwhelming your gut.

Drink to thirst on easy runs. On hot days or runs lasting more than 90 minutes, replace some of what you sweat with a drink or tablet that contains sodium and other electrolytes — plain water alone can dilute blood sodium at high volumes, which causes hyponatremia, a real race-day risk.

A rough starting point: 400 to 800 ml of fluid per hour, adjusted for heat, humidity, and your own sweat rate. Finishing a long run with pale urine and no unusual swelling is a reasonable sign that hydration was close to right.

Race day is the worst day to try something new. Use the same gels, chews, or drinks in training that you plan to use on race day. Practice the timing, test what your stomach tolerates, and find out which flavors you can keep down at mile 18.

Most marathon and half-marathon plans build long runs progressively — use every long run over 75 minutes as a fueling rehearsal. If a product upsets your stomach, switch to another early enough to adapt, not in race week.

Knowing your expected race time also helps you plan how many hours of fueling you will actually need. The anystride pace calculator can estimate that from a recent race or a current fitness level.