Introduction to Energy Gels

Diego Tobias
Apr 24
12 min read

Updated: May 13

Energy gels are portable packets of concentrated carbohydrates designed to quickly fuel endurance athletes during long runs. They “provide portable and easy-to-digest calories from carbohydrates that deliver immediate and sustained energy without the stomach distress”. In a marathon (or other endurance event), the body’s stored glycogen depletes after roughly 90 minutes, so taking in 30–60 g of carbohydrates per hour is widely recommended to prevent “bonking” (premature fatigue) Gels typically combine simple and complex carbs (often maltodextrin plus fructose) to give both a rapid and steady energy release. Runners carry them in pockets or belts and consume them with water at regular intervals (e.g. every 30–45 min) during training and races. Because they are already in fluid form, they can be swallowed quickly without chewing, but they often require drinking water (to dilute their osmolarity) – with a few notable isotonic exceptions.

Popular Energy Gels

GU Energy Gel

GU Energy Gel is one of the most widely recognized brands for runners. Their original gels (100 kcal) typically contain about 21–23 g of carbs (blend of maltodextrin and fructose), ~50 mg sodium and 0–40 mg caffeine depending on flavor. GU offers a huge variety of flavors (chocolate, fruit, dessert, etc.) and some caffeinated versions (e.g. Caramel Macchiato, Espresso) with ~40 mg caffeine. The consistency is smooth and easy-to-swallow, and GU has a loyal user base. Because their dual-carb formula (maltodextrin + fructose) fuels muscles in an “express lane,” it provides a steady energy stream.

Pros: Widely available; dozens of flavor options (both caffeinated and non-); smooth, palatable texture; relatively low cost. Easy on the stomach if taken as directed (GU gels advertise minimal GI distress). Caffeine-containing gels (typically ~20–40 mg) can give a small boost when needed.

Cons: At only ~21–23 g carbs per gel, a single GU gel contains fewer calories than many others. Runners needing higher carb intake may have to take GU gels more frequently. The basic GU gel has only ~20 mg caffeine (subtle effect). Some users find certain flavors too sweet or chemically aftertaste. (GU recommends carrying water because their gels are hyperosmotic.)

Maurten Gel (160)

Maurten’s Hydrogel gels (Gel 160 in particular) are premium, flavorless carbohydrate gels that use patented “hydrogel” technology. Each 65 g pouch delivers 160 kcal with 40 g carbs (fructose:glucose ratio ~0.8:1). They contain only six ingredients (water, glucose, fructose, calcium carbonate, gluconic acid, sodium alginate) – no colors or preservatives. Maurten’s hydrogel encapsulates sugars so they “carry through the stomach” more efficiently; this allows faster gastric emptying and higher carb uptake with less GI upset. In fact, research shows Maurten’s MD+FRU hydrogel produced higher exogenous carbohydrate oxidation than a standard sugar drink of equal calories, meaning your muscles can burn the carbs faster. Because Maurten gels are unflavored (often described as very mild or slightly sweet), some runners rotate between Gel 100 (100 kcal) and Gel 160 (160 kcal) depending on distance. Top athletes endorse Maurten’s tolerance and performance benefits.

Pros: Extremely high carb/calorie (40 g) in one sachet – ideal for long runs or high-intensity efforts. Hydrogel formulation promotes rapid absorption and is very gentle on the stomach, even when taking large amounts. Vegan/clean ingredients (no artificial flavors or fillers). Used by many elite endurance athletes.

Cons: Premium price (roughly double the cost of ordinary gels). Unflavored (or only lightly sweet) – some users may miss strong fruit or candy flavors. Low in sodium (about 20 mg per gel), so you’ll want additional electrolyte sources on hot days. Not typically sold in general stores (mostly online or specialty shops).

Science in Sport (SiS) GO Isotonic Gel

SiS GO Isotonic Gel was the first isotonic gel on the market. It contains about 22 g carbs (maltodextrin) and 87–90 kcal per 60 ml pouch, plus only 4–10 mg sodium. The defining feature is that its osmolality equals that of body fluids, meaning you can swallow it without any water. In practice, users report its texture is like a “warm, high-quality maple syrup” or dilute Jell-O: not solid but more liquid than most gels. In our testing and reviews, this watery consistency helped it slide down easily with minimal need to wash it down. SiS comes in several fruit flavors (Apple, Orange, Lemon & Lime, Tropical, Cola, etc.), plus caffeinated (+75 mg) and electrolyte (+118 mg sodium) variants. Because it has no sugar (all maltodextrin), the label shows 0 g “sugars” per serving.

Pros: Truly drinkable (no water needed), making it very convenient during a race. Easy on the stomach and less likely to bloat (“isotonic means equal osmotic pressure to body fluids”. Moderate calorie (≈90 kcal) and 22 g carbs per pack – fine for hourly fueling. Certified Informed-Sport (screened for banned substances). Available also in caffeinated and high-electrolyte versions for added flexibility.

Cons: Contains only moderate carbs per pack; ultra-endurance runners may need multiple gels per hour (or combine with drink mix). Some find the texture too thin or the taste too subtle. Non-caffeinated version has no stimulants and very little sodium (only 4 mg; those needing salt should use the “+ Electrolytes” version. Slightly more expensive per serving than mass-market gels.

Clif SHOT Energy Gel (discontinued)

Note: Clif Bar has officially discontinued its SHOT gel line as of 2023. (They now recommend Clif BLOKS chewables instead.) Historically, Clif SHOT gels were 34 g pouches with about 100 kcal (≈25 g carbs) and ~95 mg sodium=. Flavors included Razz, Vanilla, Cherry, Chocolate, etc., with some caffeinated (Citrus w/25 mg, Strawberry w/25 mg). The texture was on the thicker side (similar to syrup).

Pros: When available, Clif gels offered 100 kcal and a good chunk of sodium in a standard pouch. They had a fairly sweet, traditional gel flavor profile and multiple flavors (though fewer than GU).

Cons: No longer sold – runners must use alternatives like GU, Huma, or Honey Stinger. (Clif now markets BLOKS chews instead.) Relatively high sugar content (they used brown rice syrup) meant some runners reported stomach upset on long efforts.

Spring Energy Gel

Spring Energy makes “real-food” energy gels from whole foods (fruit purees, oats, nuts, etc.) and MCT oil. Flavors have names like “Awesome Sauce” (Apple Cinnamon), “Long Haul” (Peanut Butter & Fruit), “Speednut” (Nuts & Berries, with 50 mg caffeine), “Mango Mint” (30 mg caffeine), etc. A single gel is typically sold as ~15–45 g of powder mixed with liquid (the carb count can be high). Spring advertises many calories (e.g. 180 kcal, 45 g carbs for Awesome Sauce). The consistency is more like thick applesauce or a paste, thanks to real-food ingredients and MCT. Some athletes like the natural taste and sustained-release feel of these gels.

Pros: Uses real-food ingredients (berries, bananas, hazelnut, oats, etc.) and MCTs, which some say provides a steady burn and spares glycogen. Very high calorie formulas (some contain fat and protein too) – e.g. “Speednut” has ~250 kcal from nuts and honey. Unique flavors not found elsewhere. Naturally sweetened and vegan.

Cons: Recent lab tests show Spring gels significantly under-deliver on their labels. Independent analysis found the awesome sauce gel had less than half of the calories and carbs claimed. (This suggests the labels are unreliablei.) The gels are also expensive and available only online or specialty shops. The texture is very thick – some users may find it harder to swallow than a standard liquid gel. Because Spring gels rely on fruit sugars and honey, they are essentially high-carb (not keto). If choosing these, use caution and test them thoroughly in training.

Huma Chia Energy Gel

Huma Gel is a fruit-based gel built on powdered chia seeds, brown rice syrup and natural fruit. A typical Huma pouch has 100 kcal and ~24 g carbs. Ingredients are entirely natural: pureed fruit (berry or fruit blends), evaporated cane juice or honey, water, brown rice syrup, plus milled chia and sea salt. The chia adds a tiny amount of protein/fiber and helps stabilize blood sugar. Huma is known for excellent taste: reviewers call it “absolutely delicious” with real fruit flavor (e.g. Strawberry Lemonade tastes like lime marmalade). The texture is smooth (chia is milled fine and not gritty) and slightly thinner than many gels.

Huma offers both regular (caffeine-free) and Plus (double electrolytes) lines, as well as some caffeinated flavors (Mocha, Lemonade, etc. with ~25–30 mg caffeine). The company claims the gels are stomach-friendly – many users report no GI problems even in sensitive situations. Nutritionist reviews note that Huma’s macro profile (24 g carb, 100 cal plus electrolytes) is similar to GU.

Pros: Real-food, clean ingredients (“you don’t need a PhD to pronounce them”) Many runners rave about the taste (“tastes good and goes down easily”) and gentle stomach effectr Offers caffeinated and high-electrolyte options for flexibility. Good choice for anyone avoiding maltodextrin or artificial ingredients.

Cons: Low calorie per pouch – at only 100 kcal, a marathoner may need 2–3 Huma gels per hour to meet 60–80 g carb targets. Relatively expensive (fruits and chia cost more than typical gel carbs). Products can melt or become syrupy in heat (some users note clumping at high temperatures). Limited availability of flavor variety compared to GU (currently ~8 fruit and dessert flavors).

Honey Stinger Gel

Honey Stinger’s Organic Energy Gel blends organic honey and tapioca syrup for carbs. A 35 g gel provides 100 kcal, ~24 g carbs and 50 mg sodium. Because it’s honey-based, the gel tastes like sweet honey-fruit. Honey Stinger offers both caffeinated and non-caffeinated flavors: for example, Strawberry Kiwi (caffeinated, ~32 mg) and Salted Caramel Latte (caffeinated, 70 mg) along with purely fruit-based options like Mango, Fruit Smoothie, Blueberry, etc. All are gluten-free and made with organic ingredients. The consistency is relatively thin (more fluid than GU), so most runners find it easy to swallow and digest.

Pros: Natural sugars (honey + fruit flavors) that many find easy on the stomach. High electrolytes for a gel (about 50 mg sodium) in every pack. Smooth, drinkable texture means less risk of choking or needing extra water. A variety of tasty flavors, including seasonal ones (e.g. Salted Caramel Latte). Certified organic and NSF screened.

Cons: Moderate sodium only (50 mg) – on very hot runs you may want more salt. Some users find honey too sweet, and the taste can become cloying if over-consumed. Only two flavors have caffeine (one 32 mg, one 70 mg) – others are zero-caffeine. Slightly lower carb content (24 g) than premium gels like Maurten.

PowerBar PowerGel

PowerBar PowerGel Original is a long-standing gel (on the market since 1996) that provides ~27–30 g carbs per pouch. For example, the Coffee Espresso flavor (41 g pouch) has 121 kcal, 28 g carbs (maltodextrin/fructose blend), 101 mg sodium and 53 mg caffeine. Other flavors like Banana, Tropical, and Vanilla are non-caffeinated, while Apple and Black Currant contain ~50 mg caffeine. The PowerGel formula also includes electrolytes and some branched-chain amino acids (BCAAs) in certain versions (for example, the Roctane line). All PowerBar PowerGels are gluten-free and approved on the “Cologne List” for doping safety. Many endurance athletes rely on PowerGels in training and competition.

Pros: High in sodium (~100–200 mg depending on line), which aids hydration in long runs. Good carb content (25–30 g) and caloric density. Wide range of classic flavors. Trusted brand with consistent quality. The Roctane versions (espresso, salted caramel) add extra caffeine (53–100 mg) and BCAAs for very long efforts.

Cons: Some find the taste or texture overly sweet or artificial. Requires water to swallow easily (not isotonic). More ingredients/preservatives than simpler gels (some may experience minor GI sting from additives). Availability can be lower in U.S. mainstream stores (often sold in specialty shops).

link to buy https://www.amazon.com/Tailwind-Nutrition-Stickpack-Set/dp/B017M6C4I0

Tailwind Nutrition Endurance Fuel (Single-Serve Packets)

Tailwind’s Endurance Fuel is actually an electrolyte/fuel drink mix sold in cans or single-serve packets. In single-serve “Grab-and-Go” packets, it functions like a gel: one packet (2 scoops) provides 50 g carbohydrate (dextrose + sucrose) and about 630 mg sodium. Flavors include classic Tailwind (Mandarin Orange, Berry, Lemon, Watermelon, etc.), as well as caffeinated variants (“Raspberry Buzz” and “Tropical Buzz” contain organic caffeine)t. Runners mix each packet with water (typically 16–24 oz) and drink it down, so it hydrates as well as fuels.

Pros: All-in-one fuel + hydration. High sodium (310 mg per scoop) helps replace sweat losses. Clean ingredient list (just sugars, salt, small amounts of electrolytes/caffeine) means few GI issues. Flexible dosing: use one scoop or two based on race length (one packet = two scoops = 100 kcal, 50 g carbs, 630 mg Na). Top ultrarunners endorse it (e.g. Courtney Dauwalter uses Tailwind as her “backbone”). It is fully vegan, gluten-free, soy-free, etc.

Cons: It’s not a gel – you must carry a bottle or use aid stations, so it’s less convenient for pocket storage. Requires mixing or a bottle, which can be cumbersome on the run. Each serving tastes fairly sweet, so some may experience flavor fatigue. No fiber or protein (some athletes crave a bit of thickness in real gels). The need to drink water along with it means more weight (though that water is needed anyway).

Comparison Table

Energy Gel (Brand)	Carbs (per serving)	Caffeine	Notable Features
GU Original	~21–23 g (100 kcal)	0–40 mg (flavor-dependent)	Massive flavor range; dual-carb blend; 20–40 mg in some (e.g. vanilla ~20 mg)
Maurten Gel 160	40 g (160 kcal)	0 mg	Hydrogel tech for easy stomach and fast absorptionunflavored
SIS GO Isotonic	22 g (87–90 kcal)	0 mg (75 mg in caff. version)	True isotonic (drinkable without water); very low sugar; gentle on GI
Clif SHOT (discontinued)	~25 g (100 kcal)	~25 mg (some flavors)	Previously popular; now replaced by Clif Bloks
Spring Energy	Claimed 45 g (180 kcal); actual ≪20 g	30–50 mg (some)	Fruit/MCT-based real-food gels; lab analysis shows much lower carbs than labeled
Huma Chia Gel	24 g (100 kcal)	0–30 mg (flavors)	All-natural fruit + chia seed gel; very palatable.; gently on stomach
Honey Stinger Gel	24 g (100 kcal)	32 mg (Strawberry Kiwi), 70 mg (Salted Caramel)	Organic honey-based (glucose+fructose); thin texture; two caffeinated flavors
PowerBar PowerGel	27–28 g (120 kcal)	0–53 mg (Espresso)	2:1 glucose:fructose blend; higher sodium (~100 mg); also contains BCAAs in some
Tailwind (single serve)	50 g (2-scoop packet)	0–35 mg (buzz flavors)	Powder mix, 25 g carbs and 310 mg Na per scoop; fuels + hydrates; vegan/gluten-free

Sources: Brand websites and reviews as cited above. (For Tailwind, 1 scoop = 25 g carb/310 mg sodium; a full packet is 2 scoops.)

Use-Case Recommendations

Sensitive Stomachs: Try Maurten Gel or SIS GO Isotonic Gel – both are engineered for easy digestion. Maurten’s hydrogel and SIS’s isotonic formula “go smoothly from the stomach to the intestine,” reducing gut stress. Huma Gel (with real fruit and chia) is also often tolerated better than artificial gels.
Hot/Salty Sweaters: Gels with higher sodium help replace electrolytes. Tailwind’s packets (50g carbs + 630 mg Na per packet) or SIS “+Electrolytes” gels (118 mg Na) are excellent. Honey Stinger (50 mg Na) and PowerGel (100+ mg) supply more salt than typical low-salt gels. Maurten and GU have very low salt by themselves, so pair them with sports drink if running in extreme heat.
Long Marathon / Multiple Hours: You’ll need high-carb gels. Maurten Gel 160 (40 g) and PowerGel (28 g) deliver more carbs per pouch. You can also combine gels and drink mix (e.g. a Maurten gel plus Tailwind) to hit ~60–90 g/hr. For sustained fuel, gels with mixed sugars (glucose+fructose) like GU and SiS allow maximum oxidation of ~60–90g/hr.
Flavour Variety / Palate Fatigue: Huma, GU, and Honey Stinger offer the most flavors. Huma’s fruit-chia flavors (strawberry, blueberry, lemonade, etc.) are notably pleasant and can be a nice change late in races. GU has dozens of flavors from vanilla to salted caramel. Tailwind also comes in many refreshing drink flavors.
Caffeine Boost: Caffeinated gels (or coffees) can help energy and focus. GU, Huma, Honey Stinger, PowerBar and Spring all have versions with 25–70 mg caffeine. The strongest in our list is Honey Stinger Salted Caramel (70 mg) and PowerBar Espresso (53 mg). Use caffeine gels sparingly (usually in the later stages of a race or at the start if you woke late).
Keto/Low-Carb: None of the above gels are truly keto-friendly, as they’re designed for carb loading. (Even Spring Energy has high sugars despite some MCTs.) A few specialty low-carb gels exist (like certain MCT-oil gels), but they’re outside this scope. Most marathoners will need high-carb fuel to perform.
Budget Options: If cost is a concern, GU Original and PowerGel are usually least expensive per serving. These generic gels often go on sale and are sold everywhere. (By contrast, Maurten and specialized “real food” gels are quite pricey.) Another ultra-budget option (not listed above) is the unflavored $1 gels like Carbs Fuel, but those must be mixed with water and have no taste.

Conclusion

There is no one “best” gel for everyone, but by comparing ingredients and feedback you can pick what suits your needs. For example, Maurten Gel 160 is ideal for marathoners who tolerate no-nonsense gels and need maximum calories with minimal gut upset. GU and PowerGel are solid, affordable all-rounders (with many flavors and caffeinated variants). SiS Isotonic and Huma shine if you want gentle digestion and real flavors Honey Stinger offers a natural sweet taste with a moderate electrolyte kick. Tailwind’s drink-mix sachets are unmatched when you want to combine fuel and hydration in one package.

Ultimately, it pays to test your gel choices in training (as Runner’s World advises). Many marathoners carry two types (e.g. a fruity gel and a chocolate one) to avoid taste fatigue, or alternate gel and drink. Check the labels for carbs and caffeine, try different textures, and stick with what keeps you fueled and comfortable.

Sources: Information above is compiled from official product pages and reviews by sports nutrition experts and athletes. ensuring up-to-date nutritional data and real-user experiences are represented.