It's important to start experimenting with what you eat long before race day. It will take a while for your gut to adjust to eating more carbs and protein. Keep track of how each food makes you feel. Then, nix the ones that cause discomfort.

Different foods sit differently with different people's stomachs. However, there are certain foods that our registered dietitians (RDs) recommend you avoid altogether.

In the hours before running, avoid:

• High-fat meats, heavy sauces/creams, fried foods, high-fat desserts and foods prepared with a lot of butter or oil
• High-fiber vegetables like arugula, beans, broccoli, Brussels sprouts, cabbage, cauliflower and kale
• Whole grains extremely high in fiber
• Carbonated beverages
• Sugar-sweetened beverages like soft drinks, fruit drinks and sweet tea
• Alcohol

While running, avoid all of the above, and:

• Large quantities of nut butters, nuts and seeds
• Juice, soft drinks, sweet tea and energy drinks that contain more than 8 percent carbohydrate

Have more questions about how your diet can impact training?

Our RDs have also weighed in on what’s best to eat before a marathon. You can make an appointment with one of our registered dietitians (RDs).