What the experts say on carbohydrate-containing energy gels

In the world of endurance sports, carbohydrate-containing energy gels have become a staple for athletes seeking to maintain peak performance during long events. These convenient, quick-to-consume gels promise a rapid source of fuel, but how effective are they, really? To delve into the science behind these popular products and their impact on athletic performance, we sat down with Dr Stephen Mears, Senior Lecturer in Sports and Exercise Nutrition at Loughborough University to answer some of the key questions. In collaboration with Dr Stephen Mears we provide some insights on what the experts say about the role and efficacy of energy gels in endurance sports.

A: The body has two main sources of fuel for endurance exercise: carbohydrates and fats. When exercising intensively, your body uses mainly carbohydrates as an energy source. However, the stores of carbohydrate are relatively low and typically after 60-90 minutes of intense exercise, can be depleted ^[1-3]. Fat is a more abundant resource but is much less efficient than carbohydrate. Fats are slower to break down into usable energy and it would mean you need to reduce the intensity of your performance, and/or train less hard. Therefore, if you want to continue using carbohydrate as the main fuel source to maintain a high intensity there needs to be ingestion of an external source such as an energy gel that provides easily absorbable carbohydrates can help you maintain performance during a prolonged exercise session ^[4-6]. 

A: Although other foods and drinks can provide carbohydrates too, energy gels have their own advantages:
 

• They are available as a ready-to-consume and convenient format. Easily stored in a pocket or gel belt. 

• They often provide optimal carbohydrate sources that are easy to absorb. Energy gels are generally well-tolerated especially if you’ve practiced taking them ^[7-9].  

• For the equivalent amount of carbohydrates, often food sources need to be consumed in larger volumes which can place stress on the digestive system.  

• Carbohydrate intake is recommended in 30 g increments. Based on your exercise intensity and duration, you can easily determine the required number of gels to ensure you get 30 or 60 g per hour ^[4-6]. 

A: Energy gels are suitable for intense sports such as running, cycling, and team sports like football, especially when these activities last over an hour ^[1-3]. These gels are beneficial when your body’s carbohydrate stores are depleting, typically after 60-90 minutes of intense exercise ^[4-6]. Consuming an energy gel before your carbohydrate stores are empty can help maintain high performance levels.

Energy gels are generally not needed for sports sessions shorter than one hour, except in situations where you haven’t consumed carbohydrates for many hours, such as after a long overnight fast. In such cases, an energy gel can provide a quick energy boost before a short, intense morning workout, though a balanced breakfast is still preferred. 

A: Energy gels are suitable for most people performing prolonged intense exercise, like running, cycling and team sports. If you are not used to taking gels, then practice with them in training. Ensure that you are comfortable taking them and that you can tolerate carbohydrate ingestion during exercise. Practising will help you understand how your body reacts to a gel and how best to take it.

A: Maltodextrin and fructose are absorbed at different rates. The glucose from maltodextrin provides quick energy, while fructose provides slower, sustained energy ^[10-13]. In addition fructose, and glucose have different absorption pathways from the intestine into the blood. Making use of only one is like queuing for a cash register while another one is free. The combination of maltodextrin/glucose and fructose, especially at a 1:0.8 ratio, results in the best carbohydrate absorption, and helps avoid digestive issues and improves carbohydrate absorption ^[14-19].

A: Glucose and fructose have different ways of working in our bodies. They need to move from the intestines into the blood and then into the muscles and liver, which is where they are needed.

Generally glucose is the preferred carbohydrate, but there is a limit to how much can be handled in our bodies across a period of time.

Typically, the ratio of glucose to fructose in energy drinks and gels has been 1:0.5 (= 2:1, 2 g of glucose to 1 g of fructose), however more recently it has been discovered that the more optimal ratio is 1:0.8.

At the 1:0.8 ratio, more fructose can be tolerated therefore a greater total amount of carbohydrate can be provided without causing gastrointestinal upset. Thus, the 1:0.8 ratio, especially at higher intakes rates, is tolerated better and optimal for sports performance ^[14-19].

A: Some people may not be used to consuming energy gels during exercise. It’s important to practice using them in training to avoid issues during a race.

When you first start using gels they may work really well and you have no issues, whilst some people may find it takes a while to get used to consuming carbohydrates during exercise. 

A: Energy gels are commonly used during exercise to maintain a source of fuel as carbohydrate stores become depleted during long workouts. However, energy gel usage varies by individual.

The human body has a limited amount of stored carbohydrates. Energy gels can provide an extra source of carbohydrates during long workouts, when carbohydrates naturally stored in the body gets depleted. This typically happens after 60-90 minutes of intense exercise. ^[1-3]

The strategy for using energy gels varies for each individual. Some athletes take a gel just before starting a run and then at regular intervals during the race. It is important to take an energy gel before your energy runs out since it needs time to be digested and absorbed into the bloodstream to reach your muscles. During exercise, you should consume between 30 and 90 grams of carbohydrates per hour, depending on the length and intensity of the activity, which might mean taking a gel every 20-30 minutes. For shorter workouts of about 60 minutes or less, your body usually has enough stored carbohydrates, so there's less need for additional carbohydrate intake during the exercise. However, taking one before exercising can help maximize your fuel stores. 

A: There are varying factors that determine how long it takes an energy gel to work such as: 
 

• The intensity of your workout 

• Current hydration levels 

• Food and drink already consumed  

Energy gels won’t work instantly as it can take time to transport the carbohydrates to the muscles, therefore they should be consumed at regular intervals during exercise for a constant energy supply. Practice in training to find the best timing for you. 

A: Yes. When you exercise for a long time and/or at high intensity you lose fluids through sweat losses, therefore it’s advisable to take energy gels with fluids and stay hydrated during exercise to mitigate some of these losses ^{[5, 6]}.

The fluid intake may also help improve digestion and comfort, but it is important to practice both fluid and energy gel consumption during your training, to find what works best for you. 

A: If preferred, taking energy gels can be combined with taking other products. Whatever product combination you prefer, remember to practice this in a training session first to learn what works for you. For activities between 1 - 1.5 hours it is recommended to consume 30 g carbohydrates per hour and for activities between 1.5 - 2.5 hours it is recommended to take 60 g carbohydrates per hour. 

A: Yes, you can take energy gels on an empty stomach. They are often combined with fluids during exercise, which helps with absorption.

1. Stellingwerff, T. and G.R. Cox, Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations. Applied Physiology, Nutrition, and Metabolism, 2014. 39(9): p. 998-1011.

2. Burke, L.M., et al., Carbohydrates for training and competition. Journal of Sports Sciences, 2011. 29(sup1): p. S17-S27.

3. Kerksick, C., ,, et al., ISSN Position Stand: nutrient timing. Journal of the International Society of Sports Nutrition, 2017. 5(1): p. 17.

4. Jeukendrup, A., A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports medicine (Auckland, N.Z.), 2014. 44 Suppl 1(Suppl 1): p. S25-S33. 

5. ACSM, Joint Position Stand Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 2016. 48(3): p. 543-568.

6. Kerksick, et al., ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr, 2018. 15(1): p. 38.

7. Pfeiffer, B., et al., CHO oxidation from a CHO gel compared with a drink during exercise. Med Sci Sports Exerc, 2010. 42(11): p. 2038-45.

8. Guillochon, M. and D.S. Rowlands, Solid, gel, and liquid carbohydrate format effects on gut comfort and performance. International journal of sport nutrition and exercise metabolism, 2017. 27(3): p. 247-254. 

9. Hearris, M.A., et al., 13C-glucose-fructose labeling reveals comparable exogenous CHO oxidation during exercise when consuming 120 g/h in fluid, gel, jelly chew, or coingestion. Journal of applied physiology, 2022. 132(6): p. 1394-1406.

10. Foster-Powell, K., S.H. Holt, and J.C. Brand-Miller, International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr, 2002. 76(1): p. 5-56.

11. Atkinson, F.S., K. Foster-Powell, and J.C. Brand-Miller, International tables of glycemic index and glycemic load values: 2008. Diabetes care, 2008. 31(12): p. 2281-2283.

12. Rytz, A., et al., Predicting glycemic index and glycemic load from macronutrients to accelerate development of foods and beverages with lower glucose responses. Nutrients, 2019. 11(5): p. 1172. 

13. Stevenson, E.J., et al., A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise. European journal of applied physiology, 2017. 117: p. 2321-2333.

14. O'Brien, W.J. and D.S. Rowlands, Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance. American Journal of Physiology-Gastrointestinal and Liver Physiology, 2011. 300(1): p. G181-G189.

15. O'Brien, W.J., et al., Fructose-maltodextrin ratio governs exogenous and other CHO oxidation and performance. Med Sci Sports Exerc, 2013. 45(9): p. 1814-24.

16. Rowlands, D.S., et al., Fructose–glucose composite carbohydrates and endurance performance: critical review and future perspectives. Sports Medicine, 2015. 45: p. 1561-1576. 

17. Podlogar, T., et al., Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h− 1 versus 90 g h− 1 at different ratios. European Journal of Applied Physiology, 2022. 122(11): p. 2393-2401.

18. Rowlands, D.S., et al., Effect of graded fructose coingestion with maltodextrin on exogenous 14C-fructose and 13C-glucose oxidation efficiency and high-intensity cycling performance. Journal of Applied Physiology, 2008. 104(6): p. 1709-1719.

19. Shi, X., et al., Effects of carbohydrate type and concentration and solution osmolality on water absorption. Medicine and science in sports and exercise, 1995. 27(12): p. 1607-1615.