The Best Energy Gels for Running

Fast Fuel for Marathon Endurance

Running with Gels
Published: February 22, 2010


In 8 out my first 10 marathons, I’ve suffered from a lack of energy or muscle cramps in the later miles. Gels are supposed to alleviate this, but they’ve given me more problems, including a sugar crash and stomach cramps. Determined to AceMyRace, I’ve been researching the best application of gels. Here are my notes.

Hammer energy gel with 8oz. of water

My (Current) Solution

Half a Hammer gel and 4oz. (120 ml) of water every 1½ miles (2km, 10–15 minutes), starting at mile 3. (Note that I cut off the sharp corners of the packet so they don't get stuck in my RaceReady shorts.) In the future, I may add one endurolyte salt tablet to that.


Water & Gels

WaterGels (max.)Calories
Me: 10–15 mins.120 ml.4 fl.oz.½45
20–30 minutes250 ml.8 fl.oz.½15090
Hour500–710 ml16–24 fl.oz.1–22–3100–200180–270
Gel simple410 ml.14 fl.oz.1100
Gel complex180–220 ml.6–7 fl.oz.190

This is a guide only. Hover over (or click on) the links for notes. What The Manufacturers Recommend Brands

What Are Gels?

GU Orange

Gels are concentrated energy for endurance athletes. Also called “goo” (or the brand name “GU”), gels are a syrup-like mixture of carbohydrates (sugars), water and electrolytes (salts), often stored in a small, 100-calorie ‘easy-tear’ foil packet. Gels help replenish the energy and salts used in intense activity lasting over 90 minutes. During high intensity events, gels are easier to digest and more convenient to carry than other carb sources such as sports drinks (e.g. Gatorade), energy bars, energy powder and blocks.

How Many Gels For A Marathon?

Many runners use about four or five gels on a marathon — around one gel every 45 minutes, or 5–7 miles. There are, of course, the extremes. In his first marathon, Lance Armstrong famously ate “something like 13 gels” in 3 hours, which is one every 14 minutes / two miles. But that guy is not built like us. Besides, in later marathons, he came down to five gels — one every five miles or “roughly a gel every half hour.”

Hammer Apple Gel

How Quickly Do Gels Work?

According to GU: “The fructose converts quickly into an energy molecule that your muscles can tap within minutes. The maltodextrin, which makes up 70-80% of the carbohydrate blend (depending on flavor), takes several minutes longer. Because of this delay, your muscles enjoy a steady stream of energy instead of one gigantic sugar rush and a corresponding crash."

Comparing Gels

Gels Comparison

By percent complex carbs. One packet of vanilla flavor.
Hammer Carb-
Crank GU1 Clif Accel Pow-
Percent complex carbs 91 89 81 80 68 652 63 0
Carb (sugar) type:3 Complex sugar4 (>80%) Simple sugar5 (>30%)
Simple sugar type:6 F, G7 F8 F F F, G9 F, G10 F F, G11
Weight (g) 33 41 55 32 32 37 ? 37
Calories 90 110 150 100 100 90 110 120
Carbs: Total (g) 23 27 37 25 25 16 27 29
Carbs: Complex5 (g) 21 24 30 20 17 9 17 0
Carbs: Simple4 (g) 2 3 7 5 8 7 10 29
Sodium (mg) 25 50 230 55 40 90 200 50
Potassium (mg) 0 50 85 45 30 70 20 85
Protein (g) 0 0 0 0 0 4 0 0


  1. GU’s Roctane gel contains the same carbs as GU’s regular gel but more electrolytes — 125mg sodium and 55mg potassium.
  2. Accel contains protein (whey, from milk) which digests slower than complex carbs (both are about 4 calories per gram). In the Accel gel, complex carbs and protein provide 65% of energy; complex carbs without the protein is 56%.
  3. OK, I made this up. Simple sugars such as fructose are absorbed slower than complex sugars such as long-chain maltodextrin, so I arbitrarily drew a line between 20 and 30% simple sugar.
  4. Simple sugar = “Sugars” on the nutritional label. The simplest sugars are glucose (the best for running, it’s usually from plants), fructose (from corn or fruit, hard to digest), and lactose (from milk, hard to digest). Sucrose ("table sugar") is a simple combination of glucose and fructose. Dextrose is a chain of glucose and can be simple or complex, depending upon the length of the chain and the definition of simple.
  5. Complex sugar = “Total Carb” - “Sugars” on the nutritional label. These are medium- to long-chains of glucose polymers.
  6. Simple sugar types: F=Fructose; G=glucose.
  7. Hammer uses “Fruit juice” which is natural fructose and glucose, and “Natural grain dextrins” which is glucose in mediumly-complex polymers.
  8. Carb Boom uses “Crystalline Fructose” which is 98% fructose, plus “Grapefruit concentrate” and “Cranberry Concentrate” which, as fruits, are natural fructose and glucose.
  9. Clif uses “Organic brown rice syrup” which is sucrose (naturally-bonded fructose and glucose).
  10. Accel uses dextrin which is glucose polymer, and sucrose which is fructose and glucose.
  11. Stinger uses honey which is natural fructose and glucose. Stinger is the only gel not to contain maltodextrin.

Data current as of Feb 2010.


BrandAdvantageCompanyBased inWebsite
AccelProteinPacificHealth Laboratories, Inc.Matawan,
Carb Boom!Carbboom Nutrition Inc.Derby Line,
Clif BarOrganicClif Bar & CompanyBerkeley,
CrankMost electrolytesCrank Sports, Inc.San Juan Capistrano,
GUMost popularGU Energy LabsBerkeley,
HammerMost complex carbsHammer Nutrition, LTDWhitefish,
Honey StingerHoney!EN-R-G Foods Inc.Steamboat Springs,
PowerBarNestlé SABoise,

What the Manufacturers Recommend


Accel Key Lime Accel Gel Logo

Drink “150 ml.” or “4 oz. of water with each gel.”

Accel is the only gel to include protein (at a 4:1 ratio of carbs to protein). On a cycling test to exhaustion: “Subjects performed 13% longer in the carb-protein gel trial than in the carb-only gel trial. CPK levels [a biomarker of muscle damage] were significantly elevated after the carb-only gel trial, but not after the carb-protein gel trial.” — Saunders, Herrick & Luden

Carb Boom!

Carb-BOOM! Apple Carb Boom logo

“8-10 ounces of water should be consumed along with each serving of gel.” “Each gel pack [110 calories] provides enough carbohydrate to supply about 30 minutes of energy during physical activity.” “During activity lasting longer than 60 minutes, glycogen levels begin to diminish.” “Unfortunately, fat is not able to support exercise above a very moderate level (>60% VO2max) due to the slowness of fat mobilization and other limiting factors.” “In order to gain the performance advantage of carbohydrates, it is recommended that 30-60 grams be consumed per hour during physical activity. This translates into one to two servings of energy gels during each hour of exercise.” —Holly Ortlund, M.S., Director of R&D, Carb-BOOM, Inc.

Clif Bar

Clif Shot Chocolate Clif Bar logo

“Dehydration and sodium loss is also the number one cause of cramping!” “Replacing fluid and sodium is one of the trickiest tasks for an ultra-endurance athlete especially if it’s hot and humid.” “I’ve seen ultra-endurance athlete sodium needs range from 250mg-700mg per hour.” — Tara the RD at Clif Bar


Drink “14 ounces of water” per gel. “For each hour of athletic activity, Crank Sports recommends consuming 1 to 2 e-Gel packets [150 to 300 calories] and 16 to 32 ounces of water.” Crank’s gels offer “4 to 5 times the electrolyte levels of traditional energy gels.”

Crank Sports logo Crank eGel Cherry

Complex carbs: “With only 18% sugars, e-Gel provides more complex carbohydrates than other leading gels. This results in sustained energy delivery with less potential for the dreaded “BONK” that is more likely with brown rice syrup and simple sugars.”

Hydration: “each pack of e-Gel will take approximately 14 ounces of water along with it when it enters your cellular system. If you are properly pre-hydrated before your workout you will have 20 to 30 ounces of available water in your stomach and intestinal tract that can be used to assimilate the gel. If you fail to replace this water over time then you will become dehydrated and your performance will suffer as a result.” “if you down your gel with 4 ounces of water, you should consume an additional 10 ounces over the course of the next 30 to 60 minutes before moving on to your next gel pack.” “Nutritionists typically recommend drinking 16 to 32 ounces of water per hour during endurance events.”

Electrolytes in other gels are “…for taste mostly. There’s not enough in PowerGel, Clif Shot or even GU to make any impact. Only the guys at e-Gel put in enough for sustainability…” — Will Garrett, VP of Marketing for GU, in Inside Triathlon (May year?), as quoted by Crank.


Gu logo GU Roctane

Consume: “one [gel] every 30-45 minutes along the way, washed down with a few sips of fluid. For optimum results, always drink at least 24-30 ounces of fluid per hour during training and racing.” :…you can eat… up to approximately 340 calories every 60 minutes.”

Energize: “A shot of fast-acting natural fructose (fruit sugar) goes straight to work building your energy levels back up while the maltodextrin is quickly absorbed and sent to your muscles. Vital electrolytes keep your blood chemistry in line and hydration levels stable. Calcium keeps your muscles humming and caffeine adds an extra kick to your power.”

Calories: “…the body can digest roughly 350 calories per hour during exercise.” “If your metabolism is slow, then one GU every 45 minutes works fine. If you have an athlete’s metabolism, try ingesting one GU every 30 minutes and see if it agrees with you.” “Rip open the top and squeeze the entire packet into your mouth — don’t save half of it for later. GU’s recipe of carbohydrates and amino acids was created to be taken in one shot to provide you with maximum benefits.”


Hammer Nutrition logo Hammer Tropical

Consume “1-3 servings per hour … along with 16-28 ounces of plain water per hour.”

Hourly intake for “optimum exercise performance:

Complex carbohydrates “absorb at about three times the rate as simple sugars.”

Limit on calories your body “can only return (from the liver to muscle tissue) about 4.0 - 4.6 calories per minute, or about 240-280 cal/hr.”

Include protein after 2 hours “For exercise and competition that extends about two hours or more, your primary fuel should incorporate protein in a ratio of about 8:1 (by weight) carbs to protein.”

Pre-race: “…the pre-race meal should be eaten 3-4 hours prior to the event.” “After breakfast, drink 10-12 ounces of fluid each hour up to 30 minutes prior to the start (24-30 ounces total fluid intake).” “complex carbohydrates taken 3-4 hours prior to exercise raise blood glucose and improve performance.” “Eating within three hours of a race promotes faster release/depletion of both liver and muscle glycogen and inhibits fat utilization… [which] can devastate your performance.” "…muscle glycogen, the main fuel recruited for the first 60-90 minutes of exercise, remains unaffected by a nightlong fast. When you awaken in the morning, you haven’t lost your primary fuel supply, and can’t add to it by eating within an hour or two of exercise. …being hungry before an event won’t inhibit performance.” “If you feel that you absolutely must eat, consume 100-200 calories about five minutes before start time. By the time these calories are digested and blood sugar levels are elevated, you’ll be well into your race, and glycogen depletion will not be negatively affected.”


Honey Stinger Gold

Honey Stinger

Honey Stinger logo

Honey: “Honey Stinger uses honey as the main source of carbohydrates, as opposed to man-made carbohydrates commonly found in other energy gels. Studies show that honey is low on the glycemic index and therefore provides a long, steady source of energy instead of a spike and crash. Honey is also a natural source of antioxidants.”


PowerBar logo PowerBar Gel Tangerine

Hydration: “consume about 13–26 fl oz. (400–800 ml) every hour of exercise, preferably in smaller amounts taken frequently, such as 3–7 fl.oz. (100–200 ml) every 15 minutes during exercise.” “For workouts lasting more than 60 minutes, consume 30–60 grams [120–240 calories] of carbs every hour during exercise, preferably in smaller amounts consumed frequently.”


Write: why water? isotonic.

Simple Sugar

Simple sugar = “Sugars” on the nutritional label. Simple sugars are glucose (best, from plants), fructose (from corn or fruit, hard to digest), lactose (from milk, hard to digest) and sucrose (“table sugar,” a combination of glucose and fructose). Dextrose?

Accel uses dextrin which is glucose polymer often short enough to be a simple sugar, and sucrose which is fructose and glucose.
Carb Boom uses “Crystalline Fructose” which is 98% fructose, plus “Grapefruit concentrate” and “Cranberry Concentrate” natural fructose and glucose.
Clif uses “Organic brown rice syrup” which is sucrose (naturally-bonded fructose and glucose).
GU uses fructose.
Hammer uses “Fruit juice” which is natural fructose and glucose, and “Natural grain dextrins” which is glucose in mediumly-complex polymers.
Stinger uses honey which is natural fructose and glucose.

Gatorade? Fructose.

Complex Carbs

Complex sugar = maltodextrin which are chains (polymers) of glucose. The longer the chain, the longer it takes to digest.

Rewrite: What is Maltodextrin? Maltodextrin is an easily digestible complex carbohydrate made from natural corn starch. Maltodextrin is the preferred carbohydrate used in energy foods due to its solubility, low taste profile, and quick absorption. Maltodextrin is the primary source of complex carbohydrates in Carb BOOM! energy gel. 89% complex carbohydrates (maltodextrin) and 11% simple sugars.

Note: Maltodextrin can be a simple sugar (as classified on the nutrition label) if the chain of molecules are short in length. The best indicator is the phrase “long-chain maltodextrin.”

See Know Your Carbs.

Comparing Carbs

Carbs Comparison





Gu Roctane Clif Shot Bloks Nabisco Fat-Free Fig Newtons Airborne Tawari
Size 1 packet, 1.129 fl. oz., 32g 3 bloks, 30g, 1.06 fl. oz. 2 cookies, 29g, 1.023 fl.oz. 32g, 1.129 fl. oz.
Calories 100 100 90 90
Carbs: Total 25g 24g 22g 17g
Carbs: Complex (total-sugar) 20g 12g 10g 0g
Carbs: Simple, as sugar 5g 12g 12g 17g
Sodium 125mg 70mg 125mg 0mg
Potassium 55mg 20mg 65mg 0mg
Caffeine 35mg 25mg 0mg 0mg

Eat A Marathon

Spend one morning eating gels and water over four hours.

2/6/10: Every 15 minutes, half a gel packet and 7 oz water. Eight 90-calorie packets of Hammer vanilla gel. 12 oz of water with each. 24 oz water and 180 calories per hour.

Gels & Training

Should you use gels while training? Yes, if you’re experimenting (learning how to use) gels. Maybe no otherwise, as you can then train your body to survive without them, better burn fat.


Before the race: optimum is 10oz of water 10 min before race. Breakfast = 300 calories at least 3 hours before the race. Only water (no gels) for 3 hours before race. One gel immediately before the race?


Taste test? Jeff recommends: #1 : Powergel - Strawberry Banana; #2 : Carboom - Orange Vanilla

Sugar Crash (Insulin Spike)

Beware of insulin spikes, often associated with other energy gels made with lots of simple sugars. Rewrite: Each packet of Carb BOOM! gel provides enough energy for 20 to 30 minutes of exercise. In order to maintain a constant flow of enerrgy to the body, it is recommended to consume one packet per 20-30 minutes of exercise.



Salts. See electrolytes.


Discuss various vitamins etc. that manufacturers include.

Alternatives to Gels

Why Not Just Eat Chips?

Solid food is slower to break down and digest. Plus, during intense activity, your digestive system somewhat shuts down as blood is diverted to the muscles (called “gastric shunt”). So it's better to absorb an isotonic liquid than attempt to digest solid food.

From Carb Boom!: “What works best? Like all foods, it usually ends up coming down to personal opinions and experience. Any form of carbohydrate if taken in the appropriate amount will help delay fatigue during prolonged exercise. It’s important that you find out which type of carbohydrate works best with your body. Sport drinks, with their high simple sugar content, have been known to cause stomach problems in some people, yet are easily digested by others. A number of athletes choose energy bars as their carbohydrate source, while many others cite the difficulty in getting them down and the burdened requirement that lots of water needs be taken along with them. Because of these issues, scores of athletes are now turning to the cutting-edge nutrition of carbohydrate gels as their main energy source during training and competition.” — Carb Boom!.

Energy (Sports) Drinks

Something here about fructose. Most energy drinks offered on race courses use high-fructose corn syrup, typically HFCS 55 which contains 55% fructose and 45% glucose. If you’re using gels, don’t use an energy drink such as Gatorade, as that is already mixed with carbs (sugar). Consume EITHER a gel and water OR an energy drink; they’re equivalent.

Energy Bars

Rewrite: Many athletes prefer gels over energy bars because gels provide a super concentrated dose of carbohydrate that is absorbed very easily into the bloodstream. Additionally, gels are attractive because they are less “heavy on the stomach” and less likely to cause gastrointestinal distress than energy bars.

Energy Powder

Good selection of complex carbs and protein powders. But hard to carry while running. Better suited to being mixed in a bottle for biking.

Blocks (Bloks, Chomps), Beans

Solid, slower to digest. More sugar, less complex carbs.

Other Gels

Also: First Endurance EFS Liquid Shot, Lava Gel, Maxim Energy Gel, High5 EnergyGel (UK), Science in Sport GO Gel.

How To Carry Gels

RaceReady shorts with gel

Left: A gel (upside down) in my RaceReady shorts. There are seven pockets which can hold my sunglasses, many gels (including a half-opened one upright), my (tiny) cell phone, a house key, and an iPod nano.

Other ways to carry gels: Flasks (4 or 5 oz.) and a belt. I've even seen a hat that holds gels.


What is that exactly?

Leftover Stuff

Check out this book: Smart Exercise by Covert Bailey

Running Times article


“The average fit endurance athlete can perform up to 75% VO2 Maximum for 85–90 minutes before rate of pace deteriorates in the absence of refueling.” —Hammer Nutrition

Notes for the Summary Table

  1. One swallow is about 25 ml. (one fluid ounce) of water. If you’re using gels, don’t use an energy drink such as Gatorade, as that is already mixed with carbs (sugar). Consume EITHER a gel and water OR an energy drink; they’re equivalent.
  2. Gel = A 100-calorie gel packet, around 33 grams in mass, containing about 25 grams of carbohydrates (sugars).
  3. Note about calories. kJ/kcal?
  4. ml.= mililitres (spelled mililiters in the U.S.). There are 1,000 ml. in a litre (liter, l.)
  5. fl.oz.= U.S. fluid ounces. There are 8 fluid ounces in a “cup” and 16 fluid ounces in a U.S. pint (more).
  6. Simple sugar gel: one with significant amounts of fructose (>30%). Fructose is sweet and cheap but hard and slow to digest. Numbers are for a 6% solution.
  7. Complex sugar gel: one which is mostly maltodextrin (>80%). Long-chain maltodextrin is tastless but easier on the stomach, so you can consume more. Numbers are for a 10–12% solution.
  8. Water station ≈ 1–2 miles ≈ 10–15 minutes of running ≈ 1–3 km.
  9. The hourly amount of water (16–24 fl.oz.) comes from Hammer; GU says 24–30 fl.oz. per hour.
  10. This is a calculated value, and is stated in their website articles; however the packaging recommends “1–2 servings per hour.”

DISCLAIMER: This is a guide only. The actual amount of water required for optimum digestion depends on many factors including: your individual metabolism, weight, and fitness; the intensity and length of the activity; the type of gel used; and environmental conditions such as temperature, humidity, elevation, and wind. Test gel usage in your training runs beforehand to determine what works for you. Numbers are rounded for readability. Click here for the calculations.


Calculating how much water is required is tricky. Hammer Nutrition says: For their gels of mainly long-chain complex carbohydrates, “most athletes respond positively by diluting to a 10%–12% solution mix.” Gels with simple sugars such as fructose can be “absorbed at the rate of 6–8%” but race conditions “may permit only 3%–5% sugar solutions to absorb in most athletes, before stomach upset, cramping, or muscle failure occurs.” For the numbers above, I used these calculations:

Hammer’s vanilla gel contains 23g of carbs. A “12% solution mix” means that .12 of the resulting mixture is the 23g of carbs (the remaining .88 would be water). The amount of water needed is 23 ÷ .12 = 192g. The gel packet includes 10g of water (the packet’s weight of 33g - 23g in carbs, no other heavy ingredients being included). So 192 - 10 = 182g of water. Conveniently, 1g of water = 1 ml. (at 4°C, by definition) so, discounting temperature changes, 182g = 182 ml. Thus, 182 ml. (6.2 fl.oz.) of additional water is required. The resulting mixture would total 23g + 10g + 182 ml. = 215 ml. (7.3 fl.oz.). Drinking 470–700 ml. (16–24 fl.oz.) of fluid per hour, that’s (470 ÷ 192) to (700 ÷ 192) = 2.5 to 3.6 gel packets per hour. (However, the packaging says “1–2” servings per hour.) At 90 calories per packet, that’s 220 to 330 calories per hour. At “1–2” servings per hour, that’s 90 to 180 calories per hour.

Similarly, at 10% solution, the Hammer gel would require 23g ÷ .10 = 230g of water. 230g - 10g (the water in the packet) = 220g = 220 ml. (7.5 fl.oz.) additional water required. Total mixture: 23g + 10g + 220 ml. = 253 ml. (8.6 fl.oz.). Drinking 470–700 ml. (16–24 fl.oz.) of fluid per hour, that’s (470 ÷ 230) to (700 ÷ 230) = 2 to 3 gel packets per hour. However, the packaging says “1–2” servings per hour.

How about GU? GU contains 25g of carbs and 7g of water. At (using Hammer’s number) 6% solution that’s 25g ÷ .06 = 417g water required. 417g - 7g (the water in the packet) = 410ml. (13.9 fl.oz.) of additional water. Total mixture: 25g + 7g + 410 ml. = 442 ml. (15 fl.oz.). Drinking 470–700 ml. (16–24 fl.oz.) of fluid per hour, that’s (470 ÷ 417) to (700 ÷ 417) = 1 to 2 gel packets per hour. However, GU says “For optimum results, always drink at least 24–30 ounces of fluid per hour during training and racing.” So that’s (710 ÷ 417) to (887 ÷ 417) = 1.7 to 2.1 packets per hour.


Clif SHOT® is a registered trademark of Clif Bar & Company
PowerGel® is a registered trademark of PowerBar Inc./Nestlé SA
Hammer Gel® is a registered trademark of Frank, Brian David (individual) for Hammer Nutrition LTD
e-Gel® is a registered trademark of Crank Sports, Inc.

Coming soon: