Your body stores approximately 1,500-2,000 calories of glycogen in muscles and liver. Running at easy pace burns roughly 80-100 calories per mile. That means your glycogen stores can fuel approximately 15-20 miles of easy running — or about 2-3 hours for most recreational runners.
For runs under 90 minutes, you have more than enough stored fuel. Eating gels, chews, or sports drinks during a 45-minute easy run isn’t harmful, but it isn’t helping either.
When You Don’t Need Mid-Run Fuel
Easy runs under 60 minutes. Water is sufficient. Your glycogen stores are barely touched.
Moderate runs of 60-90 minutes. Still fine without fuel if you ate normally in the previous 12 hours. If you’re running fasted (first thing in the morning without eating), some runners benefit from a small pre-run snack rather than mid-run fueling.
5K and 10K races. These are short enough that glycogen depletion isn’t a factor. Fueling during a 5K provides no benefit — your stomach doesn’t even absorb the carbohydrates fast enough for them to be available during the race.
When You Do Need Mid-Run Fuel
Runs over 90 minutes. This is where glycogen depletion becomes possible, particularly at moderate-to-hard effort. Start fueling 45-60 minutes into the run — don’t wait until you feel depleted, because by then you’re too far behind to catch up.[1]
Target: 30-60 grams of carbohydrates per hour for runs over 90 minutes. This is approximately 1-2 gels, a handful of chews, or 16-24 oz of sports drink per hour.
Long race-pace runs. If your long run includes race-pace segments, the higher intensity burns glycogen faster. Fueling becomes more important for these sessions than for steady easy-pace long runs.
Marathon and half-marathon races. The half marathon is borderline — many runners can complete one without fueling, but most perform better with some carbohydrate intake. The marathon requires fueling — attempting 26.2 miles without mid-race carbohydrates guarantees hitting the wall.
Gut Training
Your gut needs training just like your muscles. The ability to absorb carbohydrates during running is limited by the number of intestinal transporters — and these increase with practice.
If you plan to fuel during a race, practice fueling during training runs. Start with small amounts (half a gel, a few sips of sports drink) and gradually increase to your race-day target. Runners who skip this step and then take 3 gels during their first marathon often experience severe GI distress.
Practice with the exact products you’ll use on race day. Different gels have different osmolality, different carbohydrate blends (glucose, fructose, maltodextrin), and different effects on your stomach. Find what works in training, not on race morning.
Water vs. Sports Drinks
Under 60 minutes: Water. You don’t need electrolytes or carbohydrates.
60-90 minutes: Water is usually sufficient. A sports drink is fine but unnecessary for most recreational runners at easy pace.
Over 90 minutes: Sports drinks or water plus separate carbohydrate sources (gels, chews). If you’re running over 2 hours in heat, electrolyte replacement (particularly sodium) becomes important to prevent hyponatremia.
The sports drink industry has a financial interest in convincing you that every run requires their product. For the majority of recreational running — easy runs under 60 minutes — water is all you need.