Why Timing Matters More Than the Specific Product
Carbohydrate fuel taken during a long effort works by keeping blood glucose available as the body's stored glycogen depletes -- but that only works if intake starts before glycogen runs genuinely low, not after. Waiting until a runner already feels the early signs of bonking means fuel is arriving after the deficit has already started, and it takes time to be digested and absorbed even once it's in.
This is why the same gel or chew can work well for one runner and seem to 'do nothing' for another -- the difference is very often when it was taken relative to effort and duration, not the product itself.
The Actual Numbers: How Much and How Often
Mayo Clinic Health System's guidance is direct on this: "During a long run or race -- generally more than 90 minutes -- aim to consume 30 to 60 grams of carbohydrates every hour"[1]. The International Society of Sports Nutrition's position stand on nutrient timing supports the same range for carbohydrate intake during endurance exercise[2].
In practice, that usually means starting intake around 30-45 minutes into a long run or race, before any real depletion has set in, and then repeating roughly every 30-45 minutes rather than waiting for a single large dose partway through. A standard energy gel carries roughly 20-25g of carbohydrate, so one gel every 30-40 minutes lands comfortably inside the 30-60g/hour range for most runners.
Practicing the Timing Before Race Day
Race day is the wrong place to test a fueling schedule for the first time -- both the specific product and the timing should be rehearsed on long training runs first, since gut tolerance for a given gel or drink at a given interval varies enormously between runners and only shows up under real duration and effort.
A simple way to build this habit: set a recurring phone or watch alarm at a fixed interval (every 30 or 40 minutes) on long runs during training, and take fuel every time it goes off regardless of how hungry or full you feel in the moment. This turns fueling from a reactive decision made mid-run into a scheduled habit that's already automatic by race day.
Adjusting for Southeast Asia's Heat and Aid-Station Spacing
Heat increases fluid loss and can blunt appetite mid-race, which makes some runners under-fuel exactly when they need the carbohydrate most -- carrying at least a small personal supply rather than relying entirely on aid-station gels is worth it on races where stations are spaced more than 5km apart, which is common outside the largest city marathons in the region.
Pairing carbohydrate intake with fluid rather than taking it dry also matters more here than in cooler climates: a gel taken with water is absorbed faster and sits easier on a stomach that's already working harder to manage heat stress, so timing fuel to line up with water stations rather than treating them as separate decisions is a small adjustment that pays off over a full marathon distance.