Long runs are essential for building endurance, but they’re also where proper fueling is really important. If you’ve ever hit the wall, bonked, or finished a long run feeling completely exhausted, chances are your carb intake was inadequate.
So, how many carbs on long runs (and during long races) do you actually need? And what does smart long run fueling look like for real runners? Keep in mind that “just getting by” with a few gels over a 3 hour run is not the same as optimizing your intra-run nutrition by making the most of your fueling strategy!
In this guide, you’ll learn:
- Exactly how many carbs to take on long runs based on duration of the run
- When to start fueling and how often to take gels or other carbs
- Simple long run fueling guidelines to follow
Whether you’re training for your first half marathon or mastering your marathon fueling, this simple approach will help you run stronger, recover faster, and avoid bonking towards the end of your run
What Is Long Run Fueling and Why It Matters
In order to run well, our bodies need to have enough carbohydrates. In order to have optimal carbohydrate availability, we can consume carbohydrates in the hours or days prior to exercise, take in carbs during exercise, and refuel during recovery between exercise sessions.
Taking in carbs during exercise is also called intra-run fueling. Over the years the guidance on this has shifted to an emphasis on taking in an optimal amount of carbs based on the duration of a run.
10 years ago most runners would take a 20 g gel every 45-60 minutes, no matter how long the run would be. Now we know that in order to actually fuel effectively we need much more than that.
What Happens When You Don’t Fuel Long Runs Properly
After about 60 minutes of exercise, glycogen stores begin to deplete. (And this is assuming that you had adequate glycogen stores to begin with).
If you are running for 60-75 minutes, this means that you can finish your run and go have a post run meal. However, if you are running longer, such as 90 minutes, 2 hours, or longer, you need to take in carbs on the run in order to replenish those glycogen stores. And you need to do that before they deplete.
If you run out of glycogen, you will get tired on your run and may not even be able to finish. You may see your pace slow down and feel like your body can’t work as well. You may also have a harder time recovering from your long run, feeling tired the rest of the day or even increasing your chance of an injury.
How Many Carbs on Long Runs Do You Actually Need?
Carb needs are based on the duration of the long run and are typically recommended in ranges. If the duration of your long run is on the longer end of the range, then try to get your carb intake to the higher end of the corresponding range.
Carb Needs Based on Long Run Duration
While you don’t necessarily need to take carbs during runs less than 60-70 minutes, it’s important to make sure your body has access to carbs before you start running.
During sessions lasting one hour, small amounts of carbohydrate, including even mouth-rinsing, can enhance performance via central nervous system effects. So if you are doing a hard speed session or running a short race you can consider taking in some sports drink to improve performance.
For runs in the 1-2 hour range, aim for 30-60 g of carbs per hour.
For runs in the 2-3+ hour range, try to take 60-90 g of carbs per hour. 90 grabs per hour can feel like alot, and this can take time to work up to.
Long Run Fueling Guidelines for Different Runners
Your carb intake may vary depending on your experience with running and taking carbs during a run. Beginners may need to start small at first in order to avoid GI upset. More experienced runnings may have a better idea of how many carbs they can handle and what sources work best for them.
Long Run Fueling for Beginner Runners
Starting with even a very small amount of carbs can help you feel better on your runs. As your body adapts you can start taking more to reach the recommended amounts.
You can try different type of carbs, such as gels, chews, sports drinks, or even real food. See what works best for you and how your stomach responds. As your runs get longer your carb intake should increase as well.
Long Run Fueling for Marathon Training
As marathon training runs get longer it is a great time to practice and increase your carb intake. Once your long runs get to be 2 hours you will want to be sure you are getting close to 60 g of carbs per hour.
As you get used to this amount you can increase your carb intake by taking your fuel more often or taking fuel with higher amounts of carbs. Do this gradually to see how your body responds.
For marathoners who will be racing for well over 3 hours, try to get to the higher end of that 60-90 g recommendation if you can do so without GI distress. And if you do have GI distress, don’t give up! You can train your gut or work with a sports RD for more individual guidance.
Long Run Fueling for Ultra Runs
When running ultras you will be spending alot of time on your feet. Many ultra runners rely on real food rather than just gels for fuel.
Lower intensity runs may require a different fueling strategy than more intense efforts, with those harder efforts requiring more than 90 g of carbs per hour.
When to Take Carbs During Long Runs
Before a long run or race it is wise to plan out your fueling strategy to determine what fuel you will use and how often you will need to take your fuel throughout the run.
When to Start Fueling on Long Runs
Start taking fuel about 30-45 minutes into your long run. It is better to take fuel based on time rather than distance since the amount of time it takes to run a mile can vary greatly from one run to the next.
How Often to Take Carbs on Long Runs
Set a timer on your watch to help you remember to fuel at certain intervals. The timing of your fuel will depend on how many carbs are in the fuel you are taking. If you are taking a high carb gel with 50 g of carbs you will be able to go longer between fueling intervals than if you are taking a standard gel with 23 g of carbs.
Also, if you are using any liquid fuel you will need to calculate this into your fueling plan.
Best Carb Sources for Long Run Fueling
There is some research that shows that fueling products that contain a blend of different types of carbs may maximize absorption at higher rates.
There are also studies that have recently found that a 1:0.8 ratio of glucose to fructose is better than a 2:l ratio. The 1:0.8 ratio is more effective for absorption, can minimize GI distress, and maximize energy delivery.
Gels, Chews, and Sports Drinks
When it comes to types of fuel, there are many options available. Popular products include gels, chews, and sports drinks. Check each brand/type to learn how many carbs are in a serving and what kind of carbs are in it.
Real Food Options for Long Runs
Using real food on long runs is also an option. This can be a little tricker because you need to find a convenient way to carry food on a run. Also, some real food options may have less carbs than gels and chews, so you could need to consume more in order to hit your carb intake goal.
Common Long Run Fueling Mistakes to Avoid
It is common to under fuel, to start fueling too late, or to forget to take fuel at scheduled intervals. Try to avoid these mistakes by going into your long run with a plan and setting a timer to help you remember when to take your fuel.
Taking Too Few Carbs on Long Runs
If you aren’t actually calculating how many carbs you need and adding up how many carbs are in the fuel you are bringing, you may end up under fueling. Do some math ahead of time to come up with a fueling plan.
Waiting Too Long to Fuel
You may feel good early on during a run and decide to wait to start fueling. This can backfire as you end up running out of energy before any fuel you take has a chance to kick in. Decide on when you will take your first source of fuel and stick to the plan.
How to Practice Long Run Fueling in Training
If you have never fueled on a run before, start slow. Look at where you are and where you want to be, then slowly increase your fueling to get there.
Once you figure out fuel sources that work well for you, stick with those.
Example Fueling Plan
Let’s say you have a 3 hour long run to do and you have been practicing fueling on all your other long runs, so you know you can handle 70-80g/hr of carbs during long runs. Since this is a 3 hour run you want to focus on the higher end of that range, at 80 g of carbs/hour.
Since you will be running for 3 hours, that means this run will require 240 g of carbs total. You are bringing 2 scoops of Skratch Labs Sports Drink, which will get you 40 g of carbs (if you drink it all). This leaves you will 200 g of carbs to get from gels, chews, etc.
Let’s say your gels of choice are Maurten Gels, with 25 g of carbs per gel, and Carbs Fuel, with 50 g of carbs per gel. You could plan to take 2 Carbs Fuel gels (100g) and 4 Maurten Gels (100g).
Your fueling plan might look like this:
- 30-35 minutes: Carbs Fuel
- 70-75 minutes: Maurten Gel
- 100-105 minutes: Maurten Gel
- 130-135 minutes: Carbs Fuel
- 170-175 minutes: Maurten Gel
- 200-205 minutes: Maurten Gel
- Sips of Skratch Labs Hydration Mix throughout, making sure to sip at least at the start of each mile and focus on finishing it by the end of the run
Keep in mind that while Maurten Gels have a 1:0.8 carb ratio, the Carbs Fuel has a 2:1 ratio. If you notice any GI distress you could consider trying other gels with a 1:0.8 ratio.
Final Thoughts on Long Run Fueling
Getting long run fueling right doesn’t have to be complicated. Once you understand how many carbs on long runs your body needs, and when to take them, you can take your long runs (and races) to the next level.
The key is consistency. Start fueling early, aim for a steady carb intake per hour, and use long runs to practice what you’ll do on race day. Over time, you’ll learn what types and amounts of carbs work best for your body.
Remember, long runs aren’t just about time on feet. They are a chance to practice long run fueling so you are prepared for race day.
How do you fuel your long runs?
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3 Ways to Progress Your Running After Building a Base
Is Training By Time Or Distance More Effective For Running?
Your Step-by-Step Guide to Improving in the Half-Marathon
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Such a useful breakdown, Lisa! This really highlights how far fueling advice has come and why “one gel an hour” just does not cut it anymore. I especially like the info about the glucose : fructose ratio, I didn’t know that.
Long runs are training the gut as much as the legs!
Fueling for long runs definitively takes trial and error and every body has different needs. The type and quality of the carbs can make a huge difference as well. this guide is a helpful starting point
This is a great breakdown and I’m saving this for later use.
It’s been a while since I’ve needed to fuel for a long run, but I love how you’ve organized and explained everything.
This is such good information. I’m not sure when I’ll be running longer distances but I know that fueling properly is so important.