How to Carb Load For Your Next Race
- Claire Shorenstein, MS RD CSSD CDN
- 5 days ago
- 11 min read
Carb loading is one of those things that everyone hears and talks about in the endurance sports world, but often misunderstands. There's a lot more to it than stuffing your face with pasta the night before a race!
This post will cover everything you need to know about how to carb load for your next race to crush your performance goals, including:
What is Carb Loading?
Carb loading is a performance nutrition strategy that involves intentionally increasing your intake of carbs before a race to increase your glycogen or energy stores in your muscles and liver. This does not mean eating more food per day, but rather, reducing fat, fiber, and to an extent, protein, to make room for more carbs.
The amount of carbs that you need to eat per day during a carb load is based on your bodyweight, plus your baseline daily intake. More on that in a bit!
The number of days you spend carb loading depends on the duration of your event and how many grams of carbs you can tolerate per day. A typical carb load lasts for 2-3 days, but it can be as short as 1 day and as long as 5 days.
Historically, carb loading used to involve a period of glycogen depletion (i.e. consuming fewer carbs) followed by a carb load. Thankfully, more recent research shows this is not necessary, so skip this please!
Why You Should Carb Load
You have a limited amount of glycogen that you are capable of storing in the body. Stocking up on carbs prior to a race allows you to make those energy stores last longer and rely slightly less on outside sources of carbs, which prevents you from hitting the dreaded "wall."
You're essentially topping up your fuel tank before setting out on a long roadtrip, and the last thing you want is to run out of gas before reaching your destination.
Can you finish an endurance event without carb loading? Sure, you could, but why would you want to?
Research studies show that carb loading can improve performance by 2-3% during an endurance event. Depending on how long your race is, that could mean shaving minutes (or more) off your time, and feeling better while doing it too.
Another way to look at it is that having more carbs onboard gives you more buffer, or carb insurance, as I like to call it. It's extra helpful to have your stores as stocked as possible in case things don't go as planned and you're not able to fuel consistently during your event.
When to Carb Load
Studies support that you should carb load for any race longer than 90min. This includes events like half marathons and marathons, ultramarathons, triathlons, cycling races, and long-distance swimming. It also includes endurance activities that are not races, but that still involve you pushing yourself for long periods of times.
You do not need to do a full carb load prior to every long training session, as you're not pushing yourself as hard or going as long as you would be on race day. That said, it's helpful to practice a "mini" carb load (i.e. just for one day) before your longest training sessions so you get a feel for how to do it and which types of foods you tolerate best.
You may wonder if you really need to carb load in the following situations, so let's set the record straight:
You're running an ultra or stage race and the intensity is low: Yes, you will still benefit from stocking those glycogen stores and should carb load.
You're not "racing" your race: Yes, your body is still working hard for many hours, and you need carbs available for that. Do a carb load.
You're doing your own long adventure like an FKT or a hike. You don't need to be officially participating in an event to justify a carb load, so get to it.
You're running a very fast half marathon (under 90min): It's technically below that time threshold, but you'd still benefit from at least a 1-day carb load.
The bottom line is that increasing your carbs prior to your event or other endurance adventure will improve how you feel during whatever endurance activity you do. That doesn't just mean better performance, but also means you'll be able to have more fun out there!
How to Create an Individualized Carb Loading Plan
The goal of a carb load is to increase your carb stores, but no one wants to reach a start line feeling sick. It's important to create a carb-loading plan that makes sense for you, accounting for where you're currently at with your daily carb intake, the types of carbs that you typically tolerate, and the event that you're doing.
First, Identify Your Baseline Carb Intake During Training
Before you attempt a carb load, I encourage you to spot check your normal carb intake for a few days on an app like Cronometer. This is not a calorie counting exercise - it's to get a better understanding of where you're currently at, so you can figure out an appropriate carb loading target.
Here are some key points about carb intake during training:
Endurance athletes need 5-12g/kg/day of carbs, depending on the volume and intensity of exercise
Track your carb intake early enough in a training cycle that you have time to identify whether or not you're consuming enough
If you're not eating enough carbs, slowly increase how much you take in each day while also increasing your fluid intake (carbs hold onto water when stored in the body)
Eating adequate carbs during training will better support energy levels, performance, and health, AND also better prepare you for doing a proper carb load
This article gives tips on how to boost carb intake in a way that feels good to you
If you realize you're not consuming enough carbs (i.e. <5g/kg/day) and your event is relatively soon, then you will not feel good doing a "by-the-book" carb load. You will need to take a slightly different approach, as outlined below.
Carb Loading Guidelines for Endurance Athletes
Once you've determined where your carb intake is currently at, you then need to figure out a good carb loading daily target.
Research suggests that you should aim for an intake of 10-12g of carbs per kg bodyweight per 24hr for 36-48 hours before an endurance event. For instance, a common recommendation might be 10g/kg/day for 2 days.
Some recreational athletes find these higher carb amounts challenging to reach. In this case, a more practical target might be 8g/kg/day for 3 days. If you're fueling adequately with carbs during training (i.e. taking in at least 5-7g/kg/day), this should be a bump up but not that much above your baseline intake.
If you're not able to tolerate 8g/kg/day (e.g. because your baseline daily intake is on the lower side), you can take a modified approach:
Calculate the total number of carbs you need over three days (8 times your weight in kilograms times three)
Divide this number by 4 or 5, depending on how many days you need (if you divide by 4 and the number is too high for you, then divide by 5 instead)
Example: A 150lb / 68kg runner typically takes in 4-5g/kg/day of carbs wants to do a 4-day carb load. She needs (8 x 68) x 3 or 1,632g over 3 days, so divide by 4 to get 408g/day for 4 days. This equates to 6g/kg/day for her.
The idea is that you're still increasing your carb intake above your baseline amount, but within a range that you can actually tolerate.
Whatever number you end up with as your carb loading daily goal, take that number and divide it up into the number of meals and snacks you typically consume each day. For example, if you eat 3 meals and 3 snacks, you can figure out roughly how many grams of carbs to eat at each meal and snack.
How to Carb Load: General Tips & Reminders
In theory, carb loading sounds simple - just eat more carbs, right? But in practice, things can get a bit dicey if you don't know what you're doing, you've never practiced it before, and you don't have a plan.
Here are some general tips to guide you during your carb load:
Reach for foods that you're familiar with to reduce the chance of GI distress
Carbs are the priority macronutrient! Reduce fat and to an extent, protein, so you have room to eat more carbs
For this same reason, reduce high fiber foods like vegetables, whole grains, beans/legumes, and certain fruit
Drink more fluids as you increase your carbs, as glycogen requires water for storage
If you're struggling to get your carbs in, drink your carbs (e.g. juice, sports drinks)
It's NORMAL to gain weight during a carb load
This is temporary, and it means your body is hydrated and storing more energy
Choose clothes that are comfortable, and remember your priority is to crush your race and perform well!
Which Foods Are Best for Carb Loading?
Typically, it's recommended that athletes include a combination of complex and simple carbohydrates in the diet to support health and performance. Let's quickly break down which types of carbs are best for carb loading.
Complex carbs are higher in fiber, digested more slowly, and provide vitamins, minerals and other health benefits. This makes them great choices to have during training, but not ideal during a carb load as they fill you up more quickly and make it hard to eat enough carbs.
Examples of complex carbs include:
Starchy veggies (sweet and white potatoes, peas)
Whole grains (oats, brown rice, quinoa, farro, barley, whole wheat etc)
Beans/legumes
Fiber-rich fruits
By contrast, simple carbs are lower in fiber, easy to digest, and quicker sources of energy. This is why they are ideal during a carb load, as well as anytime before, during and right after exercise.
Examples of simple carbs include:
Milk and other dairy
Fruit juice
White bread, pasta and rice
Honey, maple syrup, jam
Sugar/candy
Sports nutrition products
Note that many athletes tolerate certain complex carbs like oatmeal and potatoes (without the skin) well during a carb load. Certain fruits, like bananas, are staples of many athletes fueling plans.
What works best will always be what works best for you, so experiment during training and see what feels good!
How to Track Your Intake During a Carb Load
There are many ways to track your intake during a carb load. Some people love numbers, others despise them. Let's dig into some different ways to do this so you can figure out which one works for you!
While building your carb loading plan, it's helpful to familiarize yourself with some common carb-rich foods. This is also very useful for day-to-day fueling during a training cycle.
For my number-loving endurance athletes, here are some popular carb-rich foods as well as their carb amounts:
This obviously isn't an exhaustive list, so look at food labels if I didn't include your favorites above.
How can you use this information? You can literally grab a pen and paper (or your phone) and map out how many grams of carbs you need at each meal and snack, and what foods you plan to eat to reach those goals.
For example, if you need to eat 130g of carbs in a meal, you could have 1 bagel with PB and 1 Tbsp jam, 8oz of OJ, and a banana. Boom - you're there!
If you don't want to count grams of carbs, you can use something called the carb exchange to think in carb "units" instead. It's a good way to visually ballpark how much you need, and I use this with my athletes to help them with everyday carb planning as well as during carb loads.
Here's how it works:
Take your total number of grams of carbs per day and divide by 15
This gives you the number of units per day, where each unit = 15g
Spread the units across all meals and snacks
This may sound complicated, but I promise - it's not. Here's the same image, but I've converted number of grams to rough number of units, so you can get a sense of how many these foods provide.
Let's say you need 525g of carbs per day. That is 35 units of carbs, which we could break up into 8 units per meal and the remaining 11 units in snacks.
Here are some example meals that give 8 units:
2 cups of cooked rice or pasta + a glass of juice or sports drink
Bagel with PB and 2 Tbsp jam + glass of juice
Oatmeal made with 1 cup dry oats and 1 cup milk + banana + honey
What if you don't want to count anything at all, not even units? An even simpler strategy is to think about what you're doing at your baseline from a visual perspective and just increase it.
For instance, if you're normally doing one fist size of rice, which is about 1 cup, do two. If you normally eat just a bagel, add a banana. You get the idea!
Do this kind of thing at all your meals, and make sure you have at least two carb-heavy snacks.
Carb Loading: Sample Meals and Snacks
So what could a high carb, lower fiber day look like during a carb load?
As always with sports nutrition, there's no one right way to do this! But here are some examples:
Breakfast could be a Bagel with PB&J + fruit OR pancakes with fruit/syrup OR oatmeal with fruit/PB. You can easily get 90g with these options - add some juice and you get even more.
Lunch could be some sort of a sandwich like turkey (or egg) on a large white roll. You can add extra salt with a soup or broth or other salty things like pretzels, and then fruit or liquid carbs to top it off.
For dinner (eat early!), a popular choice is pasta with parmesan cheese and/or salt, bread, optional 2-3oz lean protein like chicken breast, and can skip veg. Other options could be sushi with extra rice and soy sauce, or pizza without too much cheese or other heavy toppings.
Snacks during the day can be carb based energy bars, fig bars, fruit, salted pretzels, graham crackers, cereal, sports drink, gummy candies, applesauce etc.
And then if able, add an evening snack of more carbs like cereal or applesauce or whatever feels comfortable to you.
Troubleshooting Common Carb-Loading Problems
Lastly, I want to address some common carb-loading problems that I see and what you can do about them:
Lack of appetite:
It's normal to eat when you're not hungry to meet your carb loading needs.
It's really important to stick to foods that you know don't upset your stomach.
Lean into liquid carbs like juice or sports drink to reach your goals.
Constipation:
This is common because you're changing what you normally eat, and if you're flying to a race, it can exacerbate the issue.
Make sure you're drinking enough fluid (doesn't need to be plain water, choose electrolytes, juice, tea, etc). You may need around 32oz or 1L of extra fluid per day.
Gradually reduce fiber during your carb load and only go low fiber 24hr before
Include foods and drinks (e.g. coffee, apple juice, prunes) that keep you regular. Test out before long runs to make sure they work for you!
Not eating enough early in the day:
Spread your intake across your day, starting with first thing in the morning, to avoid falling behind. Otherwise, you may not hit your goal, or may feel sick later if you try to play catch up.
Not making a plan:
Hitting such high carb amounts can be hard. You're more likely to succeed if you write our a rough plan for the day, especially if you're outside of your home.
I hope you found this post informative, and I wish you all a happy carb load!
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