If you have a marathon coming up, you may be struggling to keep it together with all the planning that has gone into this event and all of the planning you still have to do. However, don’t lose track of the important things, like your diet. Proper carb loading before a marathon can make or break your performance. Here’s a quick overview on how to do it.

The idea behind carb loading is a simple one: you want your body to have plenty of glycogen at its disposal on the day of your race. After all, that is its preferred form of energy. Once your body gets through all the glycogen you have in storage, its only option is to burn through fat.

Most people would love to have a body that does that, but the middle of a marathon is not the right time for it. This is often when so many runners “hit the wall.” Your body can convert fat to energy, but it takes more work. In the meantime, you’re essentially running on fumes.

Fortunately, most carb options are perfect. This includes rice, oatmeal, bread, tortillas, bagels, pancakes and waffles. The problem often occurs when runners splurge on their toppings and end up consuming cheese, creamy sauces, oils, and butter. The same can be said for pairing these items with too much protein. Both options leave you fuller and take far longer to burn.

If you want toppings for your carbs, jam and tomato sauce should work for most. You can even eat frozen yogurt for a carb-rich dessert.

Fruit can go either way. If you eat too much fiber, stomach issues will slow you down. Bananas are a safe option. Apples, pears, and peaches will give you a healthy dose of carbs too, so long as you peel them first to eliminate unnecessary amounts of fiber.

Another important point is how to carb load. Most people think it’s only done the day before, but this is wasting your body’s potential. Instead, start a few days before the marathon to make sure you’re packing in as much glycogen as possible. Switch your normal diet so that 85 to 95% of your total calories come from carbs. Put another way, you should be consuming four grams of carbs for every pound you weigh.

Although most may panic about gaining weight before a marathon, you should be able to step on a scale and see four extra pounds if you’ve handled this process correctly.