What you should look for in sports fuel.

Glucose, isomaltulose, fructose, maltodextrin, sucrose — With so many gels, chews, powders, and bars on the market, which sugars and which ingredients should you look for in sports fuel? 

When we build our fueling game plans with our clients, we always recommend testing products through weeks of gut training, so that each person can find what works best for them. Although there are recommendations in terms of glycemic index and what ingredients to avoid in products, some people are just naturally more sensitive to certain sugars, while others respond better to certain sugars.

That’s why we highly recommend getting on our calendar at least 3 months before your event so that we have time to work with you and your unique nutritional needs through a calculated, periodized and progressive gut training program.

However, there are certain guidelines that we recommend everyone follow when it comes to finding and picking your go-to sports fueling products. 

We’ll break them down into the following categories:

  • Carbohydrate content
  • Caffeine content
  • Sodium content
  • GI risk
  • Flavor
  • Accessibility

Carbohydrate Content

The carbohydrate content is perhaps one of the first things you want to consider when purchasing sports fuel. When thinking about carb content, here are some questions to ask:

How many carbs is in one serving?

When you’re fueling with gels, chews, or anything during training or the real deal, it’s important to know how many carbs you should be consuming per hour!

We try to train our clients to hit and stay within the carb guidelines recommended by the latest scientific research [5]. So, if you’re performing endurance exercise first thing in the morning at a moderate to high intensity for more than 60 minutes, you most likely should be fueling with some carb during that exercise as you will begin your session already slightly glycogen depleted (from sleep). The longer and more intense the exercise, the higher your carb target should be. For instance, for exercise longer than 2.5 hours, we recommend our clients consume 90g of carbs per hour!

Some gels may only contain 30g of carbs in one serving (like these Endurance Tap Energy Gels with 25g of carbs), meaning that you would have to eat ~3 of them to hit your 90g carb target. Other gels may have 100g of carbs in one serving (like the PH 90 Gel with 90g of carbs), so consuming 3 of these gels might lead to GI issues such as diarrhea, bloating, stomach sloshing, stomach cramping, burping, nausea etc if your system is not used to consuming this much in one hour.

Of course, most people can’t just go from 0g carbs to 90g carbs so easily. This requires weeks and months of gut training to build up your GI system’s tolerance to eating and drinking so much while performing intense exercise, and your GI system’s ability to harness that energy.

This is why we recommend signing up to work with our practitioners at least 3 months before your race. This gives us adequate time to provide weekly, incrementally increasing carb targets and fueling strategies that you can practice before race day.

What kind of carbs are included?

By this question, we mean what sugars are used in the product? If you’ve never read the nutrition label on your sports fuel and considered what sugar forms you’re consuming, start now!

We’ll briefly break down the science by distinguishing between 3 types of carbs.

First, you have the slow digesting carbs, otherwise known as low glycemic carbs. These carbs are harder for your GI system to break down, so they stay in your GI tract longer and thereby release energy over a longer period of time. Sugars that fall into this category include fructose, corn starch, isomaltulose, and more.

Slow carbs do have some benefits including a reduced spike in glucose and a smaller spike in insulin — However, it’s important to note that fast carbs also do NOT cause significant spikes in glucose or insulin during exercise [4].

Then you have fast carbs that are higher on the glycemic index. This just means that your body can break them down more easily, so you’re able to harness the energy more quickly. Sugars that fall into this category include glucose, sucrose, maltose, and more.

Finally, you have products that contain a combination of sugars. This means that these carb blends can act on at least two different types of carbohydrate receptors in your small intestine. Thus, you’re able to increase the amount of sugars your body absorbs and more quickly break down those sugars. Your body can also tolerate a larger amount of energy when compared to energy coming from just one sugar type (ie just glucose vs a glucose-fructose combo), so you’re able to sustain your energy and performance output. This ideal combo of carbs are actually blends of different sugars in specific ratios, like:

  • Glucose and fructose
  • Maltodextrin and fructose
  • Glucose, sucrose, and fructose

For instance, a couple products that include these blends are Skratch Labs Super High Carb Drink Mix and PowerBar PowerGel.

We recommend fast carbs or combo sugar products because they are the most tolerable form of sugar for GI systems, especially during intense exercise. In other words, fast carbs have the lowest risk of GI distress.

Sodium Content

Your sodium target can vary depending on not only your unique sweat and sodium loss measures, but also the environmental conditions of your race. If it’s more humid and hot outside, you’re more likely to not only lose more sweat (aka fluids), but this also means that you will be losing more sodium while exercising outside.

Consuming too much sodium can also have negative effects on your body and performance, so you don’t just want to take salt pills without considering a fueling and hydration game plan first.

Sodium is also frequently found in carbohydrate drink mixes, so you may not need to take additional sodium in those situations. For instance, CarboRocket 333 Half Evil All in One Endurance Drink has 27g of carbs and 143mg of sodium per scoop. GU Roctane Energy Gels also offer 20g of carbs and 125mg of sodium per gel.

To learn more about fluid and sodium loss, be sure to tune into our podcast Episode 45 with Dr. Alan McCubbin, one of the world’s top researchers in this area of sports nutrition!

Caffeine Content

Each person responds to caffeine differently, so whether you’re an avid coffee drinker or not, caffeine may be an essential part of your race plan, or it might not be. Now, if you’ve never consumed coffee or tea in your life, race day is not the time to try to add a little kick of energy.

When it comes to caffeinated products, the key is timing. You don’t want to take it too early and have the spurt of energy when your body doesn’t need it. You also don’t want to take it too late and get a buzz after the race is already over.

You may also want to consider the amount of caffeine in one serving of the product, depending on how sensitive you are to the effects of caffeine. For instance, the Glukos Energy Liquid Gel in Lemon Lime has 25mg of caffeine, whereas the GU Roctane Energy Gel in Cold Brew Coffee has 70mg of caffeine.

If you want to learn more about how your genetics may influence how caffeine affects your athletic performance, be sure to check out Kyla’s article with The Ready State, Genetics, Caffeine Metabolism and Athletic Performance.

GI Risk

Generally, we want to avoid consuming foods with high fiber content and high fat content immediately before and during the race. Fiber and fat slow down our digestion, and they tend to draw blood away from our muscles and more towards our GI system to help break down those foods. This can impair your performance in several manners, the most obvious being causing GI distress like diarrhea, bloating, and more. So, be sure to check that the foods you’re consuming immediately before and during exercise are low in fiber and fat content.

This blog post only covers fueling during exercise, so if you want to learn more about how to fuel BEFORE exercise, be sure to check out our Pre-Workout Nutrition Mini-Course!

Another ingredient to watch out for is one we already mentioned — isomaltulose. Isomaltulose can cause increased risk for GI distress because it is a slower digesting carb that stays in your GI system for longer. For this reason, we actually recommend only fueling with products that contain isomaltulose, like Momentous Fuel, before or after exercise [2].


Flavor fatigue is real! Imagine being on course for 4+ hours and eating the same thing the entire time! This is not so fun and it can impede your ability to stick with your fueling game plan, meaning you’re less likely to hit your hourly carb targets, and more likely to bonk.

Be sure to find different flavors, even different textures of products to fuel with during your race. For instance, try switching between the Clif Blok Energy Chew in Strawberry and the Clif Shot Energy Gel in Chocolate. We also recommend switching between sweet and salty products. Try a GU Energy Roctane Gel then a boiled baby potato. (Did you know that pro triathlete, cyclist, and ultra trail runner Heather Jackson includes boiled baby potatoes in her fuel plan? I bet you’re going to try them now!) This will help reduce flavor fatigue and keep you on track with your carb intake!


Last, but definitely not least, is accessibility. Are you able to purchase enough gels to practice with during training and use during race day? Does your race require you to use certain products? Are you able to carry all of your water bottles on your bike? Can you open the packet of chews while running at race pace?

These are all factors that many people don’t consider until race day unfortunately, and they can all increase your nerves on the big day if things don’t go as smoothly as you had planned, which is not what we want.

Instead, you should research your race day conditions. Figure out if you’ll be able to bring your own fuel, where you can re-fuel, and how you will carry all of it. If you’re unable to bring your own fuel, find out what fuel is provided and practice with those yourself.

For instance, in the 2016 Boston marathon, Clif SHOT Energy Gels in specific flavors and Lemon Lime Gatorade Endurance Formula were offered on the course.

Use race simulations to really fine tune exactly which products you’re going to fuel and when. This is also a great way to practice opening different products. After speaking with pro cyclist Peter Stetina, we learned how opening a packet of stroopwafels (like Honey Stinger waffles or UnTapped waffles) on the bike isn’t always the easiest thing to do. PS Be sure to tune into our podcast to learn Peter’s amazing trick to ensure that your stroopwafels don’t just fall out of their package in crumbs!

If you’re traveling for your race, be sure to purchase enough to pack before your travel because you might not able to access those products in a different state or country.

What to do next.

We just threw a lot of information at you. What should you do with it?

Well, one big caveat is that we only addressed during fueling training in this blog post, so that leaves out during training hydration, before training fueling/hydration, and after training fueling/hydration. In other words, there is so much more sports nutrition to learn!

We have, however, created a Pre-Workout Nutrition Mini-Course, so be sure to check that out to learn more.

If you’re a first time runner, biker, endurance athlete who is training or racing for more than one hour, make sure that you are fueling during exercise in some capacity. Under fueling can not only harm your performance, but it can lead to an increased risk for injury — which no one wants. Start with something simple and increase your gut tolerance for more carbs (and hydration) over time. Don’t be afraid to try new products, but don’t be so adventurous on race day.

If you’re a seasoned athlete, weekend warrior, or an amateur looking to improve their performance, we highly recommend getting individualized nutrition support from our team. This is the best way to fine tune your nutrition and hydration game plan. Click here to get started.


  1. Achten, J., Jentjens, R. L., Brouns, F., & Jeukendrup, A. E. (2007). Exogenous oxidation of isomaltulose is lower than that of sucrose during exercise in men. The Journal of nutrition137(5), 1143–1148. https://doi.org/10.1093/jn/137.5.1143
  2. Oosthuyse, T., Carstens, M., & Millen, A. M. (2015). Ingesting Isomaltulose Versus Fructose-Maltodextrin During Prolonged Moderate-Heavy Exercise Increases Fat Oxidation but Impairs Gastrointestinal Comfort and Cycling Performance. International journal of sport nutrition and exercise metabolism25(5), 427–438. https://doi.org/10.1123/ijsnem.2014-0178
  3. Saris, W. H., Goodpaster, B. H., Jeukendrup, A. E., Brouns, F., Halliday, D., & Wagenmakers, A. J. (1993). Exogenous carbohydrate oxidation from different carbohydrate sources during exercise. Journal of applied physiology (Bethesda, Md. : 1985)75(5), 2168–2172. https://doi.org/10.1152/jappl.1993.75.5.2168
  4. Jeukendrup, A. E., Wagenmakers, A. J., Stegen, J. H., Gijsen, A. P., Brouns, F., & Saris, W. H. (1999). Carbohydrate ingestion can completely suppress endogenous glucose production during exercise. The American journal of physiology276(4), E672–E683. https://doi.org/10.1152/ajpendo.1999.276.4.E672
  5. Jeukendrup A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports medicine (Auckland, N.Z.)44 Suppl 1(Suppl 1), S25–S33. https://doi.org/10.1007/s40279-014-0148-z
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