Fueling for Summer Long Runs: How to Prevent GI Distress on Your Long Runs in the Heat

Fueling for Summer Long Runs

In most of the United States and Canada, the weather is hot, humid, and at times unpleasant outside. It’s summer: there’s nothing novel about this weather. However, the changes in temperature and humidity do require you to adapt your running for the summer months.

If you are training for a long distance race (half marathon, marathon, or even ultra) during the summer months, you find that your tried and true fueling plan no longer works as well as it did during the colder months.

Physiologically speaking, your body is not burning more carbohydrates on long run when it’s 40 degrees or 80 degrees outside. However, your long runs may be taking longer than normal in the heat and humidity as you adjust your pace; your normal gel or chew of choice may suddenly not sit well on your stomach or its flavor may suddenly disgust you; and you find yourself more prone to bouts of GI distress.

The heat itself can slow gastric emptying during a run. In order to sweat and cool the body, blood circulation alters during a run in hot weather. Blood flow increases towards the surface of the skin so that sweating may occur, but this means less blood flow to other parts of the body including the stomach. As a result, GI distress occurs, especially as you try to take in fuel.

Meanwhile, dehydration and electrolyte imbalance can also lead to slowed gastric emptying and GI distress including nausea, vomiting, stomach cramps, and the dreaded runner’s trots. Dehydration is more likely to occur during long and/or hard runs in the heat, which creates a high risk of GI distress on summer long runs. 

You don’t have to accept GI distress or skip your long runs this summer. In addition to adapting your pace to heat, running during cooler periods of the day, drinking water during your run, and taking in electrolytes, you take avoid GI distress on summer long runs by employing these tips for fueling for your summer long runs.

Fueling for Summer Long Runs: How to Prevent GI Distress on Your Long Runs in the Heat

Fueling for Summer Long Runs

Try a new gel/chew or opt for alternative fueling methods.

Salted caramel GU may have worked for you in the winter months, but on your first summer 12 miler the thick texture and heavy flavor may seem vomit-inducing.

I’m a firm believer in adapting training, including fueling and hydration, based on your body’s needs and your goals. If something doesn’t work, adapt and find a new solution. You may need to adapt your fueling methods during the summer months, particularly what products or foods you use to fuel.

I personally prefer Hammer gels, which contain less sugar than many other gels or chews, have a lighter flavor, and don’t have a thick, difficult-to-eat texture. 

Other options include switching from gels to chews, dried fruit, or a sports drink such as Tailwind (specifically designed to prevent GI distress). When in doubt with a new fuel to try for summer long runs, opt for a palatable, mild flavor and light texture.

Take your fuel in smaller portions.

Taking a whole GU in one swig puts all of those sugars (not to mention all that volume) into your stomach at once, meaning that there’s more to digest at once. While this method may be awkward and less the ideal for race day, on your long runs take small sips of gel or a couple of chews or pieces of dried food few 20-30 minutes, rather than one gel every hour.

Why? This method puts less volume in your stomach at any given time and lets your body metabolize a smaller amount of carbohydrate before adding in more. Less volume and more time to digest should decrease the risk of GI distress.

Stephanie Howe, who’s a sports nutritionist working on her Ph.D and an nationally acclaimed ultra runner, explained in this Runner’s Connect podcast how eating more frequently during a race reduces the occurrence of GI distress. Taking fuel or food every 30 or so minutes keeps blood flow coming to the stomach and promoting a good rate of gastric emptying.

By extension, this logic would apply to summer long runs as well – taking smaller, more frequent sips of gel or bites of food will promote gastric emptying rather than letting blood flow divert from your stomach and then flooding it with a bunch of carbs after an hour or so.

Run without fuel. 

This method does not work for every runner, and I would not recommend it to novice runners who are new to long runs or for any level of runner completing a long run exceeding 2 hours in duration. 

Running without consuming carbohydrates during the run, or what I like to call low carb long runs, can get you through a medium distance long run on a day when no fuel sounds agreeable in the heat. 

When I say low carb, this is an issue of semantics: low carb runners are neither glycogen depletion runs (because they do not exceed two hours) nor are they fasted runs (in which you begin running in a fasted state with no food beforehand).

Training low carb means you eat a pre-run snack beforehand, such as a banana or toast, but do not consume any carbohydrates during the run itself. These runs do not exceed two hours for most runners, because your body has enough glycogen stored for two hours of easy to moderate running (presuming you eat enough to keep your glycogen stores full).

These should not be fast long runs, since running at or faster than marathon pace burns a higher percentage of carbohydrates and relies less on fat than do easy-paced long runs.

Additionally, low carb runs should not be done every week, as to not deplete your glycogen or risk overtraining. If you suffer from any medical issues such as low blood pressure or diabetes, consult a doctor or nutritionist before adding this types of runs into your routine.

But if a 90 minute long run falls on a particularly hot summer day and you cannot stomach the thought of any sports nutrition product or food during the run, don’t force it. Eat beforehand, take in water and electrolytes during the run, and be sure to refuel well after the run.

Low carb runs also offer possible performance benefits for marathoners and half marathoners, but that topic deserves its own post.

Master Your Fueling and Hydration eCourse for Runners 6 Week Course: Learn how to create an individualized nutrition and hydration plan for your best running! 6 Week e-Course Straight to your Inbox| Lessons, Worksheets, & Guidance from a Running Coach | $75

Want to learn more about how you can improve your fueling and hydration for running? I offer comprehensive email course for runners to help you prevent GI distress, avoid bonking, and master your fueling and hydration before, during, and after your training runs and races.

For $75, this email course includes 7 in-depth modules, worksheets and formulas so you can individualize  your fueling and hydration plan, and individual feedback on your fueling and hydration plan from me, a RRCA and Run-Fit certified running coach. Learn more about the Master Your Fueling and Hydration for Runner e-course here and register to start today!

Disclaimer: While I am a certified running coach, I am not a registered dietician. Always do what works best for you, your running, and your overall health.

What’s the worst flavor of GU/gel that you’ve tried?
Maple bacon GU and salted caramel tie for me. At first I thought they were decent, but now that I switched to Hammer Apple Cinnamon the sticky sweetness makes me gag.
How do you adjust your fueling for summer long runs?

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25 Responses

  1. I don’t really like Gu anymore, but I can do Hammergels or Honey Stinger Energy gels. Over the past few years I have only done marathon training in the summer/fall when its warm out, so I feel like my fueling has been geared towards warm weather. i’m excited to learn more from your course though and make some tweaks to my fueling plan before my next race!

    1. Same here – Hammer just is so much easier to take down than GU. I can’t even stand the smell of GU anymore, it almost makes me gag! I’m excited for you to take the course and to hear what you think of it.

  2. Fuel is such a tricky thing for runners to get down pat. It seems like it switches yearly – for me at least! It’s funny that you mentioned Salted Carmel as your least favorite. It was my favorite during the winter months. The GU was kind of hard from the cold. I tried it during the summer and gagged. Too runny and warm. Yuck!!

    1. I agree – it’s a constantly adapting thing and what worked previously won’t necessarily now. Just another thing to keep running interesting I suppose. And eewwwww to the runny GU – I think that’s why I didn’t like salted caramel – I tried it training for my first marathon over the summer months!

  3. I really like the raspberry hammer gels! once I found it on the first try so I never even tried another flavor! I used jelly beans before switching to this gel and only take a little bit at a time. I don’t know what would happen if I ate it all at once and I don’t want to find out!

    1. You really can’t go wrong with hammer’s flavors! The apple cinnamon and peanut butter are my favorite. I would be so worried about choking on a bunch of jelly beans at once or worse!

  4. My problem is that I’m doomed before i event start. Let’s just say that I may not be riding horses any more, but I do my fair share of trotting! But alas, there isn’t much I can do about that.

  5. I really don’t like Gu at all. I don’t do a lot of intra-run fueling, although I had some sport beans recently and liked those. I have been drinking nuun occasionally, so I guess that is fueling. I normally don’t like it but when it’s super hot out, the flavor doesn’t taste as bad.

    When I did take Gu, I always ate half of one at one time. I guess whole ones might work better for some runners but I’m pretty small so it was better for me to consume 50 calories now then 50 a little later in the run.

    I do agree with dehydration = gastric distress… has happened to me several times and I’ve been glad we didn’t buy a home any further back in the neighborhood.

    1. Nuun is so good for mid-run fueling – although I agree, it tastes much better on a run than after or before. I can imagine dehydration is a common problem to face in Charleston with how hot and humid your weather is!

    1. Good! I’m glad that you found it useful. Lighter and less sweet are definitely factors in handling fuel key – and I find that for some runners (myself included) less chewing helps as well for long distance running. Hopefully Tailwind works well for you!

    1. Thank you – I am glad you found it helpful! A good strategy does make summer runs so much better – anything to make them easier and more tolerable because the heat itself can be so oppressive!

  6. Well, you know I’ve been a runner forever, and so the only gels available back in 1998 were Power Gels and they were GROSS. Traumatized, I stuck to Gus for a long time (Vanilla Bean) but now I am back to Power Gels! I love the texture now!

    1. I can only imagine how gels were grosser before the sports nutrition industry grew like it did in the past decade – ick! I’m glad you found one with a good texture that you like – texture is everything with a gel (and let’s be honest – food in general).

  7. I like GU, sometimes. It helps if I kind of um… chew it, before I swallow it, but my favorite is always Gatorade, because it just goes down a lot smoother.

    That’s a really good idea to try going without fuel if you can. I have been able to do that on shorter ‘long’ runs.

    1. Gu does need to be chewed – which is so counter-intuitive for a gel, but it does help. And thank you – I find in summer it really does help, and on those “shorter” long runs it doesn’t affect performance for some people so there’s no concerns there – and well worth it for a happy stomach.

  8. I have not tried any of the gels or chews because I am so sensitive to smell and taste that I’m too scared to try….I know that’s the worst thing you’ve probably heard any runner say about fueling. I bring sour gummies and for the last long run, I had the dried sour plum with me. I eat the sour gummies but I always wonder how many little gummy bear should I be eating every 45 min? I only eat one but maybe that’s not enough? But I just cannot think about eating more than that because even with this just one gummy bear it takes a bit for me to chew and swallow and be okay with it….. Ahhh fueling. Maybe this is the cause of my unloving relationship with long runs???

    1. Some gels do have a cloying smell to them, especially GUs – the smell of those makes me feel sick as well! I can’t tolerate them anymore That’s why I like Hammer, the smells and flavors are more natural and mild. Most runners find success with 20-30 grams of carbs every 45-60 minutes over 90 minutes, so how many gummies depends on the brand. I do offer a Fueling & Hydration e-course for runners to help with fueling on long runs in particular, since it is such a tricky and individual thing.

  9. Great tips, I am currently experimenting with new fuel options! Too funny about the salted caramel, I like them! Haha. I tried the Vega gels for the first time this past weekend during a long run and HATED them. Going to try a new more “natural” options before I revert back to GUs.

    1. Thank you! Everyone has different flavor preferences and I think that experimentation is key! I hope you find some natural options that work well for you!

  10. Every gu I have tried ( not hammer) has irrated my stomach 🙁 I’m going to try generation ucann for gu and see how that goes!

    Next weekend I’ll try the hammer gel ?

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