Fall marathon season is around the corner and if you're running New York City, Chicago, Berlin, Marine Corps, or any of the other big ones that are just around the corner, you're probably already well in to your longer training runs. That means you’re looking at 30+ miles/week—even early on in the game. And the big day itself is (obviously) 26.2 miles which takes most men 4 hours, 13 minutes, and 23 seconds, The Guardian reports. With that much exercise, the type and amount of food you're eating during your runs is key to enhancing performance. 

Exercising for over 90 minutes depletes energy and naturally compels the body to search for fuel. Our muscles get that fuel primarily from stored carbohydrates and stored fat—but, our carbohydrate stores are more limited than our fat stores making it vital to replenish them before it’s too late (think: "bonking" or hitting "the wall" at mile 20.) Plus, it's not just about your performance: If your carb levels run low (or worse, run out), your body is forced to revert to your protein stores for energy, which prevents that protein from building muscle. 

So, what should you eat? The best way to find what works for you is to experiment in your training so come race day, you're not trying something new (this is marathon running 101: Never try anything new on race day whether that's new shoes, apparel, foods, or drinks!) And while every runner's needs are different and dependent on their personal goal, there are certain things that are pretty good bets—and others that definitely don't work. That's why we spoke to three experts on the topic: Marni Sumbal, R.D., an exercise physiologist and founder of Trimarni Coaching and Nutrition, New York Sports Med Running Director Francis Diano, and Elizabeth Corkum, New York City-based running coach and ISSA certified specialist in sports nutrition.

While their preferences vary, they agree on the basics: For optimal marathon performance, go for foods (roughly 100 calories every 45 minutes) with ample amounts of carbohydrates (30-60g per hour) and electrolytes to help you beat the bonk, fuel your muscles, give you a boost of energy, and replenish the nutrients you lose through sweat. Ditch any food high in fiber which could cause an upset stomach and maybe a porta potty trip (or two.) Sticking to easy-to-eat foods is also smart.

Click through for our top marathon fuel picks. Just don't forget to also hydrate out there!