How to Fuel your Run

sarah cuff Carb-Loading for Runners, Ergogenic Aids, Nutrient Timing, Running Performance 1 Comment

As a sports nutritionist who works primarily with runners, one of the most common questions I get asked is what to eat before running. You’d think by now I’d have a short, quick answer because I’ve now worked with so many runners, teach sports nutrition at the Canadian School of Natural Nutrition as well as workshops on the subject, continue to read a vast number sports nutrition and running nutrition books and texts, constantly read up on the latest science and what the elites are doing, and forever am experimenting extensively on myself.


But the reality of it is this… It depends. We’re all different with unique requirements and in varying situations. So what should you eat before you go for your run…? It depends.

Isn’t that the most annoying answer?!! Ha, I’ve always disliked answers like that. While I can appreciate the complexity of each of us as runners, just tell me how to fuel myself properly please and thank you! Besides, as different as we all are, there’s a lot of commonalities also.

With all this in mind, I’m going to tackle pre-run fueling here and now because it’s such an important topic (plus one I could happily talk and write on for hours). Let’s start with why we want to bother eating at all before we run.

The reasoning behind properly fueling your run

The goal of fueling properly in the hours before you run is to ensure your muscle and especially liver glycogen stores are completely topped up. This is to prevent you from fatiguing too early in your run. Indeed, according to Burke & Deakin in Clinical Sports Nutritionthe depletion of liver and/or muscle glycogen stores is a major cause of fatigue during exercise.

We can store between 100-120g of glycogen in our liver – and it’s our liver glycogen (and blood sugar) that fuels our brain and metabolic functions. Our muscle glycogen stores don’t share – so even if we have stored muscle glycogen, once the the liver runs low our brains will tell us to stop despite still having stored muscle glycogen. Think of topping up your liver glycogen as a way to keep your brain (and you!) happy and feeling good while you’re running.

An overnight fast reduces liver glycogen stores by about 50%. Avoiding carbohydrates during the day will also lead to a fall in liver glycogen stores. By choosing carb-rich meals and snacks prior to running, we are both ensuring we enter the run with full liver glycogen stores. So theoretically at least 50g carbohydrate needs to be consumed pre-run (and that’s just for liver stores).

While muscle glycogen stores are important also, it takes at least 24 hours to fill glycogen stores – meaning day to day nutrition plus optimal recovery nutrition is key to ensuring good muscle glycogen stores for each run.

What about running on empty? Should you ever run first thing in the morning before breakfast without eating first? Maybe. It depends (ha, thought you’d like that).

Running on empty (a fasted or carb-depleted run) can be useful. It can help train your body to burn more fatty acids as fuel (instead of glucose, aka carbohydrates), and therefore decrease your odds of hitting “The Wall” in endurance events. Click here to read more and determine if running on empty is something you should try. Personally, I do 3-4 carb-depleted runs per week and find this form of training to be extremely beneficial to my racing goals.

dsc_0026 (1)

When and how much to eat:

You might start fueling 4 or more hours in advance, or maybe 2 to 4 hours pre-run, or maybe 1 to 2 hours, or maybe only minutes before. Is there a right or wrong? Not really – it’s really based on the individual their situation. Here are the options:

Fueling 4+ hours pre-run: consume 2-4g of carbohydrate per kg of bodyweight

You might think, my gosh, I’ll never wake up to eat 4 or more hours prior to my run to eat that early!! But you’re probably thinking of a morning run. In reality, many runners run in the evening, at least some of the time if not the majority of the time – and all noon hour or evening runners fall into this category.

Say for example you run at 6:30pm… You’re going to want to begin consuming food that will fuel your run at lunch or earlier. Your lunch and afternoon snack are best chosen with your goal of having a strong run in mind. If you run at lunch, your breakfast and morning snack will be what fuels your run.

As a total aside but important to note, if you suffer from digestive issues, what you eat 12-24 hours in advance of your run will negatively or positively affect it; and if you suffer from food intolerances, knowingly or not, what you eat all the time will affect your run.

It’s likely that the only time you’d actually wake 4 hours before a morning run to eat might be a distance race such as the marathon, an ultra or an Ironman – and even then it’d likely be best to properly carb-load the day before and capitalize on sleep in the morning (or wake up, eat, and go back to bed for a few hours).

Fueling 2 to 4 hours pre-run: consume 1-2.5g of carbohydrate per kg of bodyweight

This is the most often used time-range for eating in the morning pre-race (but not necessarily morning training runs). It’s also part of the important timing window for later in the day runs.

Fueling 1 to 2 hours pre-run: consume 1-1.5g of carbohydrate per kg of bodyweight

This is most likely at least how long you’d want to eat in advance of fueling a long morning run (i.e. long Sunday runs). It may also be the timing window for eating prior to short races (such as 5k or a 10k, or even a half marathon). Again, an important top-up period for later in the day runs.

Fueling 0 to 60 minutes pre-run: consume 15-25g to 1g/kg bodyweight

If it’s within 5 to 20 minutes of walking out the door, choose an amount closer to 15-25g of carb. If you’re more towards a full hour pre-run, choose up to 1g of carbohydrate per kg of bodyweight. Carbs eaten in this period of time must be very easy to digest and provide the last possible top-up for liver stores before you hit the road. If you haven’t been eating in the earlier windows, chances are high you’ll need to rely on gels/chews to keep you going if you’re running longer than an hour.

*note – to determine your bodyweight in kg, take your bodyweight in lbs and divide by 2.2


What types of food to consume

Generally, you want to choose foods that are low in fibre, lowish in fat and lowish in protein (to ensure full digestion prior to beginning to run and to prevent GI issues). This depends on the intensity of your run though – the harder the run, the simpler the food chosen beforehand should be.

Timing matters too – the closer you get to the time you start running, the simpler the food choice should be. Bananas, medjool dates and sports gels/chews are typically very easy and fast to digest making them ideal options for consuming immediately prior to running.

Beyond that, various juices and smoothies, whole grain dishes, muffins/cookies make with oats and/or oat flour, fruits and starchy vegetables all work well. The further out you are from your run, the more fibre, protein and fat you’ll be able to be fully digest before you run. A full meal with moderate amounts of protein and fat can typically be consumed 4 hours or more prior without issue (unless it’s race day, then keep everything thing simple for 12-24 hours prior).

There are many, many various combinations and foods that would work within the many scenarios – below you’ll find just a few timing and food examples.


Eating 4 hours+ in advance (for a 6pm run): example provides 137-194g carbohydrate *provides minimum carb/kg without optional choices and up to 3g/kg by utilizing optional choices for a 150b runner (who would require 136-272g carb in this timeframe)

  • 10:00am (morning snack) – Eat2Run Power Cookie (oat-based,16g) and a Green Smoothie (24g)
  • 1:00pm (lunch) – Eat2Run Hearty Rice Salad (or a rice dish containing ¾ cup cooked rice <¼ cup dry> plus veggies such as carrots, 48g) with an optional apple (24g)
  • 4:00pm (snack) – 3 Eat2Run Mini Banana Muffins (banana and oat based, 31g) with 1/2 cup tart cherry juice (18g)
  • 5:30pm – (optional) Beet Elite shot [ergogenic aid] (8g)
  • 5:45-5:50pm – (optional) a banana (24g) with sips of water 
  • 6:00pm – run


Eating 2-4 hours in advance (for a 8am race): example provides 98-168g carbohydrate *provides about 1.5g carb/kg without optional choices and up to maximum recommended amount by utilizing optional choices for a 150b runner (who would require 68-170g carb in this timeframe)

  • 5:00am – 2 slice toast (34g) with nut butter and 1 sliced banana or 4 tsp honey (24g), sprinkle of hemp hearts (2g) with optional 1/2 cup tart cherry juice (18g)
  • 5:30/6:00am – (optional) 2 cups beet juice (52g) [ergogenic aid]
  • 7:00am – 1 medjool date (18g) with (optional) triple shot Americano (or espresso) [ergogenic aid – 225mg caffeine]
  • 7:45-7:50am – 5 Skratch chews (20g) with sips of water
  • 8:00am – race


Eating 1 to 2 hours in advance (for a 6am tempo run): example provides 83g carbohydrate  *provides about 1.2g carb / kg for a 150b runner (who would require 68-102g carb in this timeframe)

  • 4:45am – Qi’a instant oatmeal (23g) with 1 tsp each honey and maple syrup (10g) and 1 banana (24g) plus 2 Tbsp hemp hearts & walnuts (2g) with a strong matcha (1 Tbsp) [ergogenic aid – 210mg caffeine]
  • 5:45am – 1 Honeystinger gel (24g) with sip of water
  • 6:00am – tempo

As you can see there are potentially unlimited combinations of pre-run timeframes and pre-run foods that might be utilized. My suggestion is to calculate your numbers and draw up a few examples you think might work for you that meet at least the minimum carbohydrate amount of your range.

One of the biggest indicators on which foods and timeframes work best for you is to keep trying different combinations until you land on something that consistently makes you feel energized and strong throughout your workouts. It took me years to get there, but having finally landed on exactly what works for me pre-run and pre-race is such a relief – it means I can put more energy and focus on my actual training knowing I’m well fueled for a strong run.

To deliciously healthy food and stronger faster running… Cheers,


Sarah J Cuff, RHN

Comments 1

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.