If your summer long runs were a battle against your own stomach, relief is coming. Sports dietitians say autumn's drop in temperature and humidity does more than make running pleasant again — it changes how your body handles carbs, so your fueling plan needs a seasonal revamp.
The science is straightforward. In the heat, your body diverts blood to the skin to cool down, leaving less for the digestive tract. Digestion slows, gels and chews sit in your stomach, and appetite nosedives — which is why hitting 60 or 90 grams of carbs per hour in July often ends in nausea or worse. Cooler weather reverses all of that, making it easier to actually eat and absorb what your training demands.
Before a run, the guideline is 1 to 4 grams of carbohydrate per kilogram of body weight, timed 1 to 4 hours out. A 150-pound (about 60 kg) runner heading out at 4 p.m. might eat roughly 270 grams of carbs four hours ahead — think a grain bowl, or a sandwich with soup and fruit. An hour before, the target drops to about 68 grams: a smoothie or yogurt parfait.
During the run, intake scales with duration. For sessions of 30 to 75 minutes, a small hit of carbs is enough — even swishing a sports drink around your mouth can help. For 1 to 2 hours, aim for 30 grams of carbs per hour, sipping a sports drink every 15 minutes or using a gel or chews. Stretch to 2 to 3 hours and the goal doubles to 60 grams per hour, say two gels or a gel plus 16 ounces of sports drink. Beyond 2.5 hours, you're up to 90 grams per hour from a mix of liquids, gels and sports foods.
Whatever your numbers, the gut needs training just like the legs. Dietitian Allison Knott stresses practising fueling on any session over an hour. Beginners should start with a sports drink — carbs, fluid and electrolytes in one — then move to gels, then chewable options like gummy chews or dried fruit. Test new products on short, easy weekday runs, not race-pace long runs, and build intake gradually: if you're targeting 60 grams per hour, start near 30 and increase week by week. By four to eight weeks out from a race, your longest runs become a full dress rehearsal for race-day nutrition.
And if race week brings a freak heatwave? Don't scrap everything. The main adjustment is fluid and electrolytes — sweat losses climb with temperature and intensity, so dial up your hydration in the days before and on race day. A sweat rate test helps you know exactly how much: weigh yourself before and after a run, add fluids consumed, and divide by duration. One worked example: a runner dropping two pounds while drinking 20 ounces over an hour sweats at about 52 ounces per hour. Crucially, keep the fueling products you trained with — race day is not the moment for anything new.
Why it matters for travellers: if you're a runner who plans holidays around autumn races or destination marathons, this is the season your stomach finally cooperates — and the window to lock in a fueling routine you can trust anywhere.
