Chicago Marathon Fueling Plan & Pace Chart

Chicago Fueling Strategy

Chicago is the flattest major marathon in the world. This is both a gift and a trap for fueling. The flat terrain means you can push pace aggressively and fuel consistently without worrying about hills disrupting your stomach. But it also means runners go out too fast and neglect early fueling because everything feels easy.

The biggest variable at Chicago is weather. October conditions range from a perfect 45°F to a brutal 75°F+. The 2007 race was cancelled mid-race due to heat. Your fueling plan needs a hot-weather contingency.

Cool conditions (under 55°F): This is PR weather. Go aggressive on carbs. Target 80-90g per hour or higher if you've trained for it. The flat course means your effort stays steady, which is ideal for gut absorption. Take your first gel by mile 2-3 and maintain every 20-25 minutes. You can push the upper end of your carb range here because your body isn't fighting heat stress.

Warm conditions (55-70°F): Scale back your pace goal by 5-10 seconds per mile and shift your fuel mix toward more liquid calories. Gels become harder to tolerate as core temperature rises. Consider using drink mix for 30-40% of your carb intake and gels for the rest. Increase fluid intake at every aid station.

Hot conditions (70°F+): Survival mode. Slow your pace 15-30 seconds per mile. Prioritize hydration over carbs. Switch to primarily liquid calories (sports drink, drink mix). If you're still taking gels, chase every one with 6-8 oz of water. Add sodium (aim for 500-700mg per hour). Your total carb intake will naturally drop, and that's OK. Finishing healthy matters more than hitting a carb target.

Regardless of weather, the miles 18-22 stretch through Chinatown and Pilsen is where Chicago breaks people. There's less crowd support, the sun can be brutal on exposed streets, and you've been running on concrete for 2+ hours. Front-load your fueling in miles 3-15 so you have a buffer here.

The final 3 miles back to Grant Park along Michigan Avenue have great crowd support but also a headwind off the lake. If you've been disciplined about fueling, this is where you reap the reward. If you skipped gels early because the flat course felt easy, this is where the bill comes due.

Chicago has 20 aid stations, roughly one to two miles apart. Each serves lemon-lime Gatorade Endurance Formula first, then water, both at every station rather than alternating. Gatorade Endurance Formula carries 22g of carbs and 310mg of sodium per 12oz in a 2:1 glucose-to-fructose blend, so two race cups is about 20g. If you're using the on-course Gatorade as part of your plan, factor those carbs into your total. Maurten Hydrogel Fuel Depots (Gel 100 and Gel 100 Caf 100) are at mile 12.4 and mile 18.1 only. Four Culligan refill stations before aid stations 4, 7, 12 and 16 let you refill a flask or vest.