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Energy Gels:

 Does the new fad in sports nutrition really improve Click to enlargeendurance?

Click to enlarge                                  




By Christine Gerson




When athletes are involved in long endurance events, it is extremely important for them to maintain enough energy so they can get through the entire event.  In order to so this, they need to make sure that they are maintaining and replacing their depleted carbohydrate stores (muscle glycogen).  With all the sports nutrition products on the market that claim to help athletes with replacing these carbohydrate stores, it is often difficult to know which ones to use and to know if they even work at all.  Energy gels are the newest product that athletes are using and so the question becomes: does the new fad in sports nutrition really improve endurance?


I. What are energy gels?



Energy gels are most often described as a mix between energy bars and sports drinks, which results in a gel that is made up of an extremely concentrated amount of carbohydrates in a pudding-like consistency.  The gels are intended to give “fuel” to athletes so that they are able to sustain their energy levels (for 30-45 minutes) during an endurance activity.  They are often sold in 1.1 oz or 1.4 oz packets and come in a variety of flavors ranging from vanilla and banana peach to apple cinnamon (



Most energy gels have between 100-110 calories, 23-28 grams of carbohydrates, and between 20mg-50mg of caffeine per serving (  All brands contain complex carbohydrates and aim to keep simple sugars low.  There is no fat, fiber or protein in the energy gels, but rather some brands (like GU Energy Gel) are made up of glucose molecules (like maltodextrin), fructose, sucrose and water (  Some other brands (like Honey Stinger Natural Energy Gel) add natural honey, electrolytes, and vitamins to their ingredients (



Where are they found?

            Energy gels are sold in small individual packets that typically cost around $2.00 and can be found in any bicycle, fitness, or outdoor store and in some drugstores as well.


Who uses them and why?

Many athletes, especially cyclists and runners, are starting to use energy gels during longer endurance events in order to replenish their depleted carbohydrate source so they have an extra energy boost.  The gel is intended to give the athlete the complex carbohydrates, glucose, and electrolytes that he needs during his high intensity activity.  Although mostly amateur and professional athletes use energy gels now, companies are hoping that recreational sports participants will begin to use them as well since they too will find the gels helpful in multi-hour activities such as skiing or hiking.


            Athletes often prefer this gel form of a sports enhancement because they are quickly digested into the blood stream.  Unlike sports bars, they are light and “ ‘not heavy on the stomach’” and therefore do not cause gastrointestinal distress.  They are often more convenient to carry during an endurance event and more easily consumed during this type of event than a sports bar (


When do people use them? How should they use them?

            Athletes and recreational sports participants use energy gels during an athletic event when they feel like they need a supplement to help them sustain their energy.  Typically, it is recommended that 30-60 grams (or one to two servings) of the gel be consumed per hour of an activity.  For an activity that lasts less than two hours, 30-60 grams of gel should be consumed before starting the exercise and a second energy gel should be taken 45-60 minutes into the activity.  For an activity that lasts longer than two hours, one energy gel should be taken an hour into the activity and then gels should be consumed every 30-45 minutes throughout the remainder of the activity (

            However, since energy gels are concentrated carbohydrates, they provide no fluid, which is an important aspect to consider, along with carbohydrate supplementation, for helping endurance performance.  Therefore, for every 1.4 oz of gel, it is recommended that an athlete should drink 500 ml of water.  If an athlete is dehydrated and does not drink enough liquid along with the energy gel then he may inhibit a fast absorption of both the carbohydrate and water, which will result in a lower performance (


II. What are the most popular energy gel brands? What do they do for you?


1. GU Energy Gel: This gel claims that it will “keep your mind alert and active, and your muscles going strong.”  It is good for quick absorption, does not make your stomach fill full, and maintains an optimum blood sugar level.  It is the 80% maltodextrin to 20% fructose ratio that allows your glucose level to be maintained for 45 minutes of exercise. It also contains 20 mg of caffeine  (


2. CarbBoom Energy Gel: This gel has 22-25 grams of complex carbohydrates and 2-4 grams of simple sugars that gives the gel a “ ‘not too sweet’ taste and is gentle on the stomach.”  This gel contains 50 mg of caffeine (


3. PowerGel: Powergel is said to be a concentrated form of carbohydrates that is packed with 28 grams of simple and complex carbohydrates to give an immediate energy boost.  It also contains 180 mg of electrolytes (sodium, potassium, and chloride).  PowerGel contains 25-50 mg of caffeine (


4. Clif Shot Energy Gel: This gels markets its products specifically towards performance-orientated athletes and they claim that their product not only tastes great but is beneficial since it uses organic grown ingredients, mainly brown rice syrup.  It also contains  40 mg of caffeine (


5. Honey Stinger Natural Energy Gel: Honey Stinger is all natural, made with pure honey and vitamin B complex which helps in the absorption of proteins and fats and the breakdown of carbohydrates into glucose.  Since it is made of honey, it has a low glycemic index, which prevents an energy high followed by a crash and is a great source of antioxidants (


III. Claims made by advertisements:


How do energy gels work?

Energy gels are said to give athletes energy by replenishing carbohydrate energy stores that are depleted during physical activity.  Although fat is the largest source of energy that the body uses, it is slowly mobilized and thus is not able to give the body a very good source of fuel for an activity above 60% VO2max.  Since most athletes train and compete at a level greater than this, they depend on the preferred energy source of carbohydrate to supply them with the energy that they need ( It was found that when energy gels (25 grams of carbohydrates) were consumed with 200 ml of liquid, the body was able to maintain its blood glucose levels at 70% of VO2 max on a two hour run as compared to a placebo (

The body stores carbohydrates in two forms: glycogen and glucose.  Glycogen is stored in the muscle and liver and is a branched molecule made up of glucose units.  Glucose, on the other hand, is stored in the blood and is therefore is an even better energy source than glycogen.  It is thus extremely important that the limited carbohydrate stores are restored during moderate to heavy exercise since as activity goes on, the body uses these stores for the energy that it needs in order to sustain the intense level of exercise (


How does carbohydrate ingestion improve endurance performance?

            When your body is at rest, carbohydrates travel through your blood stream and are stored in the liver and skeletal muscles as glycogen.  During exercise, your liver breaks down the glycogen into glucose and delivers it as a main source of energy to your brain.  At rest, the glycogen stored in your muscles (the main source of energy) isn’t used very much at all.  However, during endurance exercise, your body uses carbohydrates to provide energy ( Therefore, after about 60 minutes of endurance exercise, the body’s glycogen levels begin to fall and the body begins to use blood glucose as its main source of fuel.  Therefore, if carbohydrates are ingested when muscle glycogen levels are low, they help to maintain the right levels of blood glucose to prevent early exhaustion.  At higher levels of exercise, carbohydrates perform another function of preventing and delaying glycogen sparing (which is the depletion of muscle glycogen) (


Why add caffeine to energy gels?

            Recently many sports related products are adding caffeine into their list of ingredients.  Why is this? Caffeine is said to be beneficial for maintaining an athlete’s energy during endurance events (over two hours) as well as for short-term intense exercise (five minute maximum output exercise).  Many athletes report that by consuming caffeine before an event, they feel a mental burst of energy, increased focus and motivation.  In order to gain these benefits from caffeine, it is suggested that an athlete should consume 2 mg per pound of body weight one hour before exercise.  However, there have been few studies on the actual benefits and effects of caffeine ingestion during the athletic event.  Thus, to insure maximal effects of caffeine it is important to make sure that an athlete actually uses the energy gel in the proper proportions one hour before competing.  In addition, even though caffeine is a diuretic, athletes should not be concerned about the effects of caffeine on hydration.  Studies have shown that “no changes occurred in core temperature, sweat loss, plasma volume, urine volume or body hydration status during exercise following caffeine ingestion” (

            It is still unclear exactly how caffeine promotes its effect on the body, however there are three main theories that exist to help explain its actions on the body:

1)     Central Nervous System:  The idea is that caffeine would help the athlete to feel better and to be more alert by acting on the central nervous system.  In response to caffeine, the CNS would stimulate nerves to make muscle contraction move faster and increase focus and clear-headedness.

2)     Skeletal Muscle: When caffeine is ingested, it works to stimulate changes in calcium activity, which in turn causes ion transport of potassium into non-contracting muscles.  Through this transport, the typical rise in plasma potassium that happens during activity is reduced.  This reduction helps to maintain muscle fiber excitability and allow for a longer muscle contraction.

3)     Metabolism: Caffeine is said to increase the early release and mobility of free fatty acids into the blood, which helps to increase muscle fat oxidation and lower carbohydrate oxidation.  Therefore, muscle glycogen is spared and can be used for later use during exercise (

There are however some concerns with the intake of caffeine during exercise.  It is possible that caffeine causes “increases in heart rate, impairments or alterations of fine motor control and technique, and over-arousal” ( In addition, there could be potential interactions between caffeine and other supplements that athletes are taking which at the current time have yet to be explored in terms of performance side effects (



IV. What does the research say?


Does carbohydrate ingestion really work to improve endurance performance?

            There are many studies that do support the findings that carbohydrates are effective in giving athletes the energy that they need to compete for longer during endurance events.

 One study by Jentjens and Jeukendrup (2005) looked at whether high rate of carbohydrate (in a mixture of glucose and fructose) ingestion would lead to peaked energy performance during a prolonged cycling exercise.  They hypothesized that “a mixture of glucose and fructose when ingested at a high rate (2:4 g/min) would further increase the rate of exogenous CHO (carbohydrate) oxidation (>1:3 g/min)” (Jentjens & Jeukendrup 2005).  They tested eight trained male cyclists or triathletes around age 26 who performed three exercise trials on a stationary bike.  Each trial consisted of 150 minutes of exercising at 50% of their individual power output (Wmax) while drinking either a glucose drink, a glucose and fructose drink, or plain water.  The results of this study conclude that when glucose and fructose were ingested together at a rate of 1:2 and 1:2 g/min (respectively), this combination resulted in peak performance where exogenous CHO oxidation rates were 1:75 g/min.  When the athlete consumed this combination of carbohydrates, he was able to perform at about 50% higher exogenous CHO oxidation rates than when we just consumed glucose alone.  Jentjens & Jeukendrup (2005) explain that intestinal CHO absorption is increased when this mixture of multiple CHO is ingested and thus helps to increase the exogenous CHO oxidation (Jentjens & Jeukendrup 2005).  Therefore, this study supports the fact that energy gels would help to increase endurance performance for athletes.

            Another study by Coggan & Coyle (1988) further supports the fact that carbohydrate ingestion during prolonged exercise helps to maintain higher exercise intensities.  This study investigated “the highest steady-state exercise intensity and associated rate of carbohydrate oxidation that could be maintained by well-trained cyclists after 2-3 h of intense exercise, when plasma glucose availability was maintained by carbohydrate ingestion” (Coggan & Coyle 1988). They tested seven male trained cyclists (ages 23+/- 1 yr) and each subject completed two trials (each one week apart) where they cycled for long periods of time alternating every 15 min between 60% and 85% of their VO2 max until fatigued.  A double-blind design was used for this experiment. In one trial subjects ingested 1g of carbohydrates/kg body weight in a 50% lemon-flavored solution after 10 minutes of exercising and then .6g/kg in a 20% solution for every 30 minutes of the trial.  In the other trial the subject was given equal volumes of the liquid that was artificially flavored (the placebo).  The results of this study show that when subjects were given the carbohydrates, their plasma glucose level increased after 30 min (to 6 mM) and remained elevated (at 5.5-6 mM) for the remainder of the exercise.  Thus, glucose levels in the placebo trials were much lower. Additionally, when the subjects ingested the carbohydrates they were able to maintain higher exercise intensities (75% VO2 max) during the third hour of their exercise as compared to the placebo group (60% VO2 max).  Coggan & Coyle (1988) conclude that adequate muscle glycogen stores are needed in addition to the elevation of plasma glucose (caused by the ingestion of carbohydrates) in order to maintain high states of intensity (Coggan & Coyle 1988).  Thus, this study supports the fact that carbohydrates, and thus energy gels, work to maintain elevated levels of blood glucose needed for endurance exercising. 


Does adding caffeine to energy gels really help to sustain energy levels in endurance activities?

            Among the scientific research, there has been much controversy over whether or not caffeine actually has the positive effect on endurance performance that energy gels claim it does and through what mechanism the caffeine exerts its effects. 

One study conducted by Yeo, Jentjens, Wallis, and Jeukendrup (2005) found support for the idea that caffeine does help to increase exogenous carbohydrates oxidation.  Since they reference a previously thought fact that “intestinal absorption is one of the main limiting factor for exogenous CHO oxidation,”(Yeo et al. 2005) they hypothesized that “the ingestion of caffeine could increase the availability of ingested CHO and increase exogenous CHO oxidation during prolonged exercise” (Yeo et al. 2005) more than just glucose alone.  In this study they are interested in the effects of combing glucose and caffeine during a two-hour bike exercise on exogenous CHO oxidation rates.  They had eight trained male cyclists complete three exercise trials (120 minutes of biking at 55% Wmax) and they either received a glucose drink, a glucose and caffeine drink, or water.  After every 15 minute intervals the subjects were given 150 ml of the liquids.  The results of this study show that when both CHO and caffeine are ingested before and during the exercise trials, it delays fatigue onset and causes an increase in exercise capacity at a 26% higher exogenous CHO oxidation rate versus just glucose alone (Yeo et al. 2005). 

The study by Jacobson, Febbraio, Arkinstall and Hawley (2000) however, finds evidence that contradicts that of the above study.  They looked at the effects of caffeine co-ingested with either a carbohydrate or fat meal on metabolism and performance during prolonged activity.  They hypothesized that caffeine would result in the highest carbohydrate oxidation and the lowest rates of fatty acid oxidation (Jacobson et al. 2000).  Eight trained male cyclists performed four trials and consumed meals of either carbohydrate, carbohydrate plus caffeine, fat, or fat plus caffeine and then an hour later they then completed a 120-minute cycling exercise.  The results of this study show that when caffeine is co-ingested with carbohydrate an hour before an endurance exercise, it had a very minimal effect on both exercise metabolism and performance as compared to carbohydrate alone. In addition, caffeine had no effect on increasing fatty acid oxidation even when fat availability was at its maximum (Jacobson et al. 2000).  Thus, caffeine was not shown to provide any additional performance benefit and caffeine also was shown not to have an effect on metabolism of fatty acids, demonstrating that this is not a way that caffeine exerts its effects on the body.




Energy gels are becoming the newest development in sports nutrition as an enhancement for athletes during prolonged exercise.  Many people find that they prefer energy gels over sports bar or sports drinks because they are convenient to carry, easily digested, are quickly absorbed into the blood, and do not cause upset stomachs during performance.  There is evidence to suggest that energy gels, if ingested in the proper manner, do help to increase endurance performance.  However, there is still debate if and how the caffeine that is added in these energy gels has any beneficial effect on endurance performance.








Coggan, A..R., & Coyle, E.F. (1988). Effect of carbohydrate feedings during high-intensity exercise. Journal of Applied Physiology, 65(4), 1703-1709.


Jacobson, T.L., Febbraio, M.A.., Arkinstall, M.J., & Hawley, J.A. (2000). Effect of caffeine co-ingested with carbohydrate or fat on metabolism and performance in endurance-trained men. The Physiological Society, 86(1), 137-144.


Jentjens, R.L.P.G., & Jeukendrup, A..E. (2005). High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise. British Journal of Nutrition, 93, 485-492.


Yeo, S.E., Jentjens, R.L.P.G., Wallis, G.A.., & Jeukendrup, A..E. (2005). Caffeine increases exogenous carbohydrate oxidation during exercise. Journal of Applied Physiology, 99, 844-850.



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