Carb Loading for Your Marathon or Half Marathon (And Why Most Runners Overdo It)

Every runner I’ve ever coached has heard about carb loading. Most of them have a plan for it going into race week. And the vast majority of the time, I watch those plans go poorly.

It comes from a good place. People are motivated. But when I see someone really excited to go hard on a specific, somewhat difficult carbohydrate loading protocol, that’s usually where the trouble starts.

Think of It Like a Gas Tank

Here’s the analogy I keep coming back to. Your body is a car. Your job before a marathon or half marathon is to show up to the start line with a full tank.

Now picture this: you’ve already filled the tank, but you’re so committed to the protocol that you load the back seat with extra canisters of gasoline. Just in case. That gas isn’t powering anything. You’re just driving around with the extra weight of it.

Same is true for carbohydrate stores. There’s a point where they’re full. Overfilling them does more harm than good. I’ve had athletes tell me they felt really sluggish, felt full and stuffed, maybe felt a little extra weight on them. Lethargic going into race day.

We want to be completely full, feel good and healthy and ready to go. We just don’t want to overstuff ourselves. Carb loading is not an unlimited energy source. Our body wants the right amount, and there is a limit.

Start With Liquids

Getting a carbohydrate heavy drink into your routine makes a massive difference. Something as simple as Gatorade, Skratch, Tailwind, whatever it is. Three days out, at least twice a day, add a liquid carbohydrate mix that you normally wouldn’t have to your routine.

This knocks everything out at once. You’re loading carbohydrates, getting your hydration dialed in, and getting your electrolytes where they need to be. And because you’re drinking it rather than eating it, you’re a lot less likely to overshoot.

Whatever kind of drinks you like works here. A fun agua fresca. Your favorite flavor of Gatorade. Drinking your favorite juice a little more than usual. The key is that it has calories, carbs, electrolytes, and hydration all together.

Watch Out for Electrolyte Only Mixes

One huge mistake I see people make is reaching for electrolyte only mixes. Things like LMNT, or different mixes that go in water but are just electrolytes with no calories or carbs. Obviously then we’re not getting that extra carbohydrate energy in that we could be using for the race. Great products for other situations. Wrong tool for this job.

Keep Food Familiar and Repeatable

On the food side, as we get into that final day or two, we’re thinking about limiting fiber or things that might have certain bathroom effects. Vegetables, legumes, beans, certain types of meats or spices that could create some unwanted bathroom experiences the morning of. We don’t need that.

Really we’re just doubling down on the things we know are safe, that have very known repeatable results of how we feel when we eat them. What things do I eat that I have my best workouts on? What’s easiest to time the bathroom around? What makes me feel good and is completely repeatable?

If you’re traveling for a race, bring it from home if you can, or find something in that city that works really well for you. I have a friend who always does Chipotle the night before a marathon. Partly because it’s pretty hard to go into a race city that doesn’t have a Chipotle, so it’s incredibly repeatable. That’s the whole point.

And this is actually kind of a fun time. We get to have extra carbs. Go for dessert those days leading in. Your favorite cookie. Stop by your favorite bakery and sneak in a little extra. Not overdoing it, but treat yourself and make it fun.

Race Morning Is a Protocol You’ve Already Practiced

This is something we need to have been practicing throughout the whole training block on long runs. Deep reflection on the timing is incredibly critical.

How do we time our coffee so we get both the caffeine and the bathroom effects exactly where we want them? How do we hydrate so we don’t do too much but we’re also hydrated enough to compete? We want to give ourselves about two hours to digest our main meal and have that energy usable.

The best athletes have it completely systematized. Something like: wake up three hours before gun time, immediately have coffee, hydrate a little, eat a bagel with peanut butter and honey two hours out, take a carb mix to sip on between then and the start, maybe have a gel right before the gun to get a little extra carb and glycogen hit going in.

Whatever your version of that is, same thing. Repeatable. Something you’ve practiced. Because race morning is not the time to figure any of this out.

Honestly, It’s Overhyped

I think carb loading is incredibly overhyped.

It is sometimes viewed like caffeine. Like it’s free energy that you can just keep pulling from if you eat enough carbs. It doesn’t work that way. There’s a limit to how much carbohydrates our stores can handle. Just like any vitamin or mineral, it’s about getting the right amount for you. More is not always better.

Having enough fuel and great energy going into a race absolutely matters. We want a full tank. We just don’t want the back seat full of gas cans too.