Thinking Out Loud: Fueling For Long Runs

I thought about writing this post after recently being asked, “You need this many GUs for a 16 mile run?!” by the local sneaker store employee. It made me feel kind of embarrassed for some reason. But yes, I need that many! I am not about to bonk in my next marathon again (hopefully).


For that 16 miler, I took a GU every 3 miles. An intake of about 200 calories per hour. This is more than I see most people taking, as most take 1 every 45-60 minutes. And that’s what the instructions say too.

But I’m confused. Why do the instructions say take one every 45ish minutes, but other sources say if you’re doing a long run, or running a marathon, you should be taking in about 200 calories per hour (and 3-60g of carbs per hour)? Obviously this depends on your stomach and stuff, but why is there that discrepancy?

GU nutrition facts

This excerpt is from an article in Runner’s World, “How To Eat During Long Runs,”

In general, runners need to add in 30 to 60 grams of carbohydrate each hour that they are running longer than 75 minutes. But you’ll need to start fueling earlier than 75 minutes into a run; by that time, your tank will be empty, and once you hit empty it is very hard to recover. Start taking in fuel within 30 minutes of hitting the pavement.

This is from Active, “How To Fuel On A Run,”

To perform your best, you need between 30 and 60 grams of carbohydrate for each hour of exercise. Sports drinks like Hammer HEED, Powerade and Gatorade supply a blend of carbs, such as maltodextrin and glucose, plus water and sodium to prevent dehydration, says Nancy Clark, R.D., author of Nancy Clark’s Sports Nutrition Guidebook.

And from Mizuno,

Finally, during the marathon, you should fuel with about 200-350 calories per hour (after the first hour), as tolerated.

According to this fueling calculator, I should have a gel within the first hour, then every 4 miles after that. I somewhat adhere to this, as I  have a gel every 3ish miles.

And then there’s hydration…which I have only recently mastered…somewhat.

According to the BAA, “During training and racing, drink at regular 15 to 20 minute intervals to minimize loss of body weight to approximately 2% of your starting body weight by the end of the race.”

Now, I drink every 2-3 miles, but also when I get thirsty. On long runs, I have practices sipping on water as I run. I made a huge mistake in the last marathon, because I was only fueling and hydrating every 6 miles. Talk about a newb!

I’m hoping that my new way of fueling and hydrating will lead to a way better marathon…and not finishing dehydrated and puking…

For some people, fueling too much affects their stomach so they have to take less, but I think I have definitely benefited from learning how to fuel more often…especially because I sweat a TON.

What do you think about all of this fuel information? Do you try to get 30-60g of carbs, or 200 calories per hour in your races?

What’s your favorite way to fuel?


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  1. In my recent marathon I took 3 Gus (2 Accel and 1 PowerAde) and 1 pack of Gatorade gummies (little more than one/hour). That was plenty for me though it sounds like you plan on taking double that amount! Too much affects my stomach and causes me to feel heavy and weighed-down.

  2. I took 3 Gus during my recent half marathons, around miles 3-4, 6-7, 9-10. I feel like it keeps me going! Something else to concentrate on and I love the burst I get. I’ll be an over Gu-er during my marathon in May I’m sure!

  3. As you say, there is no magic bullet. The amount of fuel and water depends upon many factors and unique per person. I’ve hit the wall hard several times but other marathons breezed through the wall while taking the same amount of fuel as the last bonk.

    My next race is December and I’m concerned about the wall since I’m going for a BQ. Likely, i’ll need to up the fuel intake. See how my 20 miler go and use that as a gauge for the race.

    Thanks for your post

  4. My approach (two half marathons and one marathon) is to drink a lot of extra water the days leading up to the race. I hate having to stop for bathroom breaks during a race so I try not to drink too much more than the essentials during it. Being thirsty means you’re dehydrated, so maybe having a lot of extra water ahead of time will help. I drink very little the night before/morning of to try to avoid the bathroom. My friend also told me the trick of adding a few sprinkles of salt to my water bottle to help me retain more of the fluid, too.

    During the race I wear a fuel belt – it has four 8-oz mini bottles that I mix with water and coconut water (for the electrolytes instead of Gatorade). In the marathon I finished all those and probably stopped at 3 or 4 water stops. For the half marathon I used almost 3 plus two water stops.

    For the gu part – I use Honey Stinger (not a fan of all the artificial chemicals in other brands). Their packets usually have about 10 chews in each of them. Starting around mile 8, I will take about 3-4 chews every few miles if I feel like I need them. I think for the marathon I went through one and a half packets, and for my last half marathon I only had them once – 4 of them at mile 6. And, you probably know this, but always take them with some fluid to help absorption/digestions. Honey Stinger also has some waffle cookies that I used for some of my training runs for something a little different that felt more substantial, but those are harder to manage during a race because they break and get crumbly jostling around in my pack.

    Hope that helps! It’s so hard to figure stuff like this out because everyone likes different things and everyone handles things differently. Good luck!

    • Thanks for sharing! I love honey stingers as well, they’re just abit pricier than GUs. I actually tried the strawberry waffle earlier in training and really liked it but it made me have dry mouth so I figured it wouldn’t be a good idea to use. I also plan on wearing a fuel belt and carrying 2 water bottles and refilling them…somehow. Still haven’t figured that part out lol. I want to be able to sip on water when I want/need to as opposed to waiting for a water stop.

  5. I made that terrible mistake of not hydrating or refueling enough during my first marathon. I couldn’t understand why I felt like collapsing at mile 19. During the second marathon, I sipped every 10 minutes and refueled every 45. This helped tremendously, but I still don’t think I’ve completely mastered it. Don’t worry about what others are doing or how they view your plan. Bottom line – do what works for you. Good luck.


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