How to Fuel Your Big Race (Carb-Loading 101)

sarah cuff Run Faster, Running Performance 4 Comments

One of the most common questions I get is how to eat before a big race. Specifically, should I be ‘carb-loading’ the week before a race (and what does that really even mean)? What to eat the night before? The morning of? Does that mean I can eat more cookies? More oat bars?!!


Carb-loading is essentially the practice of eating enough carbohydrates (approximately between 7 to 9 grams of carb per kg of bodyweight) to ensure your muscle glycogen levels are topped up (you have the maximum energy stored) come race day. This may prevent you from ‘hitting the wall’.

You may wish to consider ‘carb-loading’ if:

  1. Your race will last more than 60-80 minutes;
  2. You are not already eating 7-9g of carb/kg bodyweight daily;
  3. You don’t have any medical reasons (diabetes, hyperlipidemia, etc) that would render carb-loading unsafe for you.

I know the question that probably came to mind when reading point #2 is, “How do I know how many carbohydrates I’m already eating?” Let me give you an example of someone who is 150 lbs (68kg) who, at 7-9 grams of carb/kg, would require 476g-612g carbs per day.

  • Breakfast: granola or oatmeal with honey/chia, with banana and almond milk = 105g
  • Snack: 3 oat bars and apple = 86g
  • Lunch: pesto pasta (1/2 the recipe) = 110g
  • Snack: cut veggies and 26 Mary’s crackers with 1/2 cup hummus = 82g
  • Dinner: quinoa loaf with mashed potato and kale/beet salad = 100g
  • Snack: 4 chocolate energy balls = 60g

Grand total = 543 grams of carbohydrates (~8g carb / kg body weight).

So if your daily dietary menu already looks like the one above, give or take volume for your weight (or if you run the numbers for what you eat and they work) – then you don’t need to worry too much about ‘carb-loading’ the week before your race. You more want to ensure you’re eating well as usual and not skipping any snacks or meals. If your diet doesn’t look like above, that just means you’ll need to add a few more more complex carbohydrates and some simple sugars like honey and maple syrup into your diet (oatmeal, pasta, hummus, whole grains, oat bars). As for more cookies – well, that’s debatable.

Personally, my daily menu looks similar to what’s above (adjusted to my weight), so what I eat in the week leading up to my race doesn’t change much. I would reduce some of my fattier foods (nuts, avocados, olive oil) and add a few more oats and fruit. My taper (50% reduction in running volume) is really what ensures my glycogen stores are full come race day.

Because the goal of eating in the week leading up to your race is to ensure you have full glycogen stores and feel energized (not lethargic and heavy from eating too much), it is important to practice your dietary strategies in advance so your body is used to the food. Get into the habit of practicing and perfecting your strategy regularly before your long run each week to ensure you perform your best on race day.

1. Two to three days out (typically Thursday/Friday, as races usually fall on Sundays)

If you need to focus on carb-loading (or in other words, aim to eat 7-9 grams of carbs per kg bodyweight), start two to three days out.

Do not eat anything new or unusual. Stick to foods you know your body can digest well. Travelling for races usually gets us in trouble – use caution when eating out and go for simple, recognizable fare. Try to find a grocery store to pick up breakfast food and snacks you are accustomed to.

Hydrate well – but again, nothing that’s ridiculously out the norm. A general rule of thumb is to drink half your weight in ounces (on a regular basis) per day. For example, someone who is 150 lbs would aim to drink ~75 ounces (9 cups) of water, juice, tea, or a natural sports drink such as Vega Pre-workout Energizer.

2. One day out (typically Saturday)

As above and avoid the following:

  • Heavy sauces
  • Fatty foods including fried foods
  • Red meat
  • Nuts
  • Dairy
  • Additionally, ease up on fibrous foods (especially if you have a sensitive digestive system) – now’s not the time to see how many veggies you can eat in one day!

3. Dinner the night before (typically Saturday night)

You want to ensure you eat dinner between 5:00pm and 6:00pm (absolutely no later than 6:30pm). It is very important to give your body time to digest your meal before the race begins. Follow the above guidelines for this dinner – it should be one you’ve already ‘practiced’. Pasta (white if required, to lower fibre) is most popular but rice or yams/potatoes work well also. Keep the sauces to low-fat tomato sauces and veggies well-cooked.

My meal the night before I ran my best ever half marathon was quinoa-kale-hummus tri-plate. It worked beautifully for me – but that was because it was a food I was very much used to – it had been well practiced.

You might wish to have a snack before bed. This is perfectly fine, just ensure it’s something like an oat bar – high complex carb, low fat. I remember a few hours after my tri-plate I had grapes and a couple squares of dark mint chocolate before going to bed. Practice what you enjoy!

4. Breakfast the morning of (typically Sunday morning)

Depending on your digestive system, you’ll want to eat anywhere from 1-4 hours before the gun goes off. But you’ll know what time to eat because you’ll have practiced it and you’ll already know what is ideal for you! Personally, I eat about 3 hours before I hit the road for a long run or race. Oatmeal is a favourite, but granola or toast work well too. Don’t shy away from using honey or maple syrup as sweeteners in your breakfast – they are great non-fibre ways to up the carb intake.

You may wish to have coffee, black or green tea or matcha tea along with your breakfast the morning of long runs and race day as caffeine is a known performance enhancer (although you want to avoid it entirely if you have a sensitive digestive system). Aim to have it at least an hour before you start running (it takes about that long for it to reach peak concentration in your system). I save my matcha tea for long run and race mornings and drink swiss water decaf the rest of the week. Again, nothing new on race day – this is something you would have practiced.

As a runner looking to perform your best on race day, it is important to look at pre-race strategies such as ‘carb-loading’. Begin practicing and figuring out what is ideal for you 6-8 weeks before race day rolls around. Your race will be a more successful one for it.

Have you ever gone into a race without practicing your race week / race day strategy? Or been in a situation that you just couldn’t eat what you were used to? Or on the other hand, have you run a race where you felt strong and know you ‘carb-loaded’ correctly? Let me know in the comments below!

Happy running 🙂


Sarah J Cuff, RHN

PS. Check out this weeks “Runner of the Week”, Jeremy Cuff. Yes, he has the same last name as me. Yes, he’s my husband. Together, we are Team Cuff (just take a look at the picture!).

Comments 4

  1. Any advice for new runners/ triathlons for type 1 diabetics? I’m on a pump. It’s been a long time since I’ve trained for anything ( was a rower pre-diabetic years). Nervous of sugars dropping during race or letting them get too high!!
    Any help is appreciated

    1. Post

      Hi Heather… I have some practical general advice but ongoing consultation with a team of qualified clinicians – including a dietitian or nutritionist with experience in diabetes management, a diabetes educator and a physician – is critical for athletes with diabetes on insulin. I’d be happy to discuss any questions you might have… Please email me ( if you would like more information, thanks! -Sarah

  2. I love the article. Isn’t caffeine a peak of two hours? I am one of the few people that has had genetic testing for stimulants and I metabolize things super fast! Within an hour of having a caffeinated beverage (or a caffeine pill which is not my preference) I begin to have a big energy surge, but unfortunately crash afterwards.

    Post-workout I feel EXHAUSTED even on short 1-2 mile runs at a slow/conversational pace. I have low Testosterone by genetics and I also am on some different medicines, but I am not wanting to let that stop me from enjoying running. I’m constantly suffering from ailments like plantar fasciitis. I recover pretty slowly though as I might have 16 oz of white skim milk and that’s it until maybe 3-4 hours my run that I might eat. I don’t get many carbs in my diet but a decent amount of protein/fats for me being 165 pounds. I drink a lot of fluid in the day but most of the beverages are acidic/low-calorie. I am looking to improve my running as I have hit a plateau hard with injuries like PF and also the unbearable fatigue I experience afterwards. To top it all off, I have asthma that I have to use inhalers for so it’s a constant battle to keep control of it as the weather changes.

    1. Post

      Good question Jacob – peak plasma concentrations occur between 15 and 120 minutes after oral ingestion of caffeine (in general most notice it within 45-60 minutes), shorter if taken on an empty stomach and longer if ingested with fibrous food, and depending on genetics. Matcha green tea may serve you better as a good energy boost that lasts (without the crash that often comes after a caffeine pill or coffee or energy drink is ingested) due to energy coming from not only caffeine but also huge amount of catechins it contains as well as L-theanine. As I’m sure you’ve noticed on this blog there’s many options you might try to help boost energy levels post-workout as well as build a stronger body less susceptible to ailments such as platter fasciitis and help manage your asthma, such as this post on post-run nutrition If you’d like personalized direction please don’t hesitate to send me an email! Best, Sarah

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