The Modern Carbohydrate Playbook: How to Fuel Endurance in 2026

Key Takeaways

• The pro peloton's "120 g/hour revolution" is real, but for most age-group athletes the performance edge over a well-executed 60–90 g/h plan is small, inconsistent, and only earned after months of gut training.
• The biggest fueling mistake recreational athletes make is mismatching intake to intensity: easy Zone 2 sessions rarely need fueling, while hard efforts over 75 minutes are dramatically undersold by "a banana and a gel."
• Recovery is mostly carbs, not the protein shake on the bottle. Hitting 1.0–1.2 g carbohydrate per kg per hour for the first 4 hours after a depleting session, plus a periodized daily total of 3–12 g/kg, moves the needle far more than any single in-race tweak.

If you want a primer on macronutrients, protein timing, and daily nutrition basics, start with our Nutrition for Endurance Athletes guide. This post goes deeper into the in-race carbohydrate science that has changed fast over the last five years.

Why Fueling Changed

Five years ago, the standard advice for long-course endurance athletes was 60–90 grams of carbohydrate per hour. The professional peloton now routinely fuels at 120 g/h and sometimes more. At the 2025 IRONMAN World Championship in Nice, Norway's Casper Stornes ran a 2:29:25 marathon, the first sub-2:30 in IM World Championship history. Media reports put his intake at roughly 175–180 g/h on the bike and 100–120 g/h on the run, though pro fueling plans are closely held and those numbers trace back to a single unsourced report.

Three things drove the shift, in order of importance:

1. Energy balance across stage races. Tim Podlogar, performance scientist at Tudor Pro Cycling, has noted that pros simply cannot eat enough off the bike to cover Grand Tour energy demands.¹ The scale of the gap is easy to sketch: a rider who moves from 70 to 110 g/h across the roughly 80 hours of racing in a three-week Grand Tour takes on about 3,200 g of extra carbohydrate, none of which they could realistically replace at the dinner table.
2. Glycogen sparing and running economy. A 2025 study of elite male marathoners showed 120 g/h lowered the oxygen cost of running by 3.6% versus 60 g/h.²
3. Brain effects. Carbohydrate in the mouth activates brain regions associated with reward and motor control, improving performance independent of metabolism. Notably, this happens without any measurable drop in perceived exertion.³

So is the right answer to copy the pros? Not quite.

What the Science Actually Shows

The honest version of the story is more cautious than the marketing.

The most recent comprehensive review of the literature, Wilson (2025) in Sports Medicine, concluded verbatim: "Existing research does not directly support performance-enhancing effects of ingesting carbohydrate at ≥ 100 g/h versus 60–90 g/h, but studies underpinning this conclusion do not closely reflect the conditions and demands that cyclists face when they participate in multi-day/multi-week stage races or intensified training periods."⁴ That second clause matters: the absence of evidence is partly an absence of the right experiments. Podlogar himself told Velo magazine: "I don't think we have any data to suggest that 120 grams of carbohydrate per hour will improve performance over 90 grams."¹

The 2025 Ravikanti marathon study, the strongest signal yet for higher intakes, tested 8 elite male marathoners through a 120-minute run just below lactate turn point. 120 g/h beat 60 g/h on running economy by a clear margin (3.6% lower oxygen cost). But there was no statistically significant economy difference between 120 g/h and 90 g/h, and peak GI symptoms (nausea, fullness, cramps) were greatest at 120 g/h.²

A January 2026 meta-analysis pooling 31 studies and 48 effect sizes found carbohydrate ingestion does spare muscle glycogen, but the effect is small (around 24 mmol/kg dry weight over ~100 minutes of exercise), and ingestion rate was not a significant moderator. Higher rates did not spare meaningfully more glycogen than moderate ones.⁵

The takeaway: 60–90 g/h captures most of the available benefit for most athletes. Going higher is for the genuinely long, hard, and well-trained gut.

The Transporter Story (and Why Ratios Matter)

Glucose and the maltodextrin polymers that break down to glucose are taken up in the small intestine via the SGLT1 transporter. Feed glucose alone and the rate at which your body can actually burn it plateaus around 1.0–1.1 g/min (60–66 g/h), which is taken as evidence that SGLT1 has saturated. Fructose crosses via a different transporter, GLUT5, so combining the two pushes that ceiling to roughly 1.7 g/min (100+ g/h). This is why every modern endurance product blends glucose (or maltodextrin) with fructose.

One caveat on the numbers: they come from tracer studies measuring how much ingested carbohydrate you oxidize, not from direct measurement of intestinal absorption. Transporter saturation is the accepted explanation for the plateau, but it is inferred rather than observed.

The ratio is dose-dependent. There is no single "magic" ratio. Asker Jeukendrup, whose lab pioneered this work, has stated plainly: "There is no optimal ratio. The ratio that is optimal will change depending on amounts ingested. If 90 g/h is ingested it should be around 2:1, but if more is ingested, for example 120 g/h, 1:1 is likely better."⁶

Total intake	Glucose : Fructose	Why
≤ 60 g/h	1:0 (glucose only) is fine	SGLT1 not yet saturated
60–90 g/h	2:1	Saturates SGLT1 with modest fructose load
90–120 g/h	1:0.8 to 1:1	Higher fructose share; SGLT1 already maxed
> 120 g/h (elite)	1:1	Maximum GLUT5 contribution

Format does not matter at a given dose. A 2022 trial showed that at 120 g/h, exogenous carbohydrate oxidation was the same whether the carbs came as a drink, a gel, a chew, or a combination.⁷ Pick what your gut and your sport can handle.

Match Intake to Intensity AND Duration

The most common amateur error is treating duration as the only variable. Intensity matters just as much.

At rest and in Zone 1–2, fat dominates as a fuel. As intensity rises there is a "crossover" point where carbohydrate takes over, and above it carbohydrate supplies the large majority of energy.⁸ Where that crossover sits depends heavily on how trained you are: in professional cyclists it arrives around 75% of maximal power output, but in moderately active people it comes as early as 55%.⁹ The fitter you get, the longer fat carries you, and the higher the intensity at which fueling becomes non-negotiable.

This dictates a simple decision tree:

• Zone 2 under 90 min: Often no fueling needed. Train fat oxidation.
• Zone 2, 90 min to 3 h: 30–60 g/h spares glycogen for tomorrow's quality session.
• Tempo or threshold over 60–75 min: 60–90 g/h. Carbohydrate need scales with intensity, not just clock time.
• Sustained high intensity over 3 h: 90–120 g/h ceiling, with gut training.

Daily Carbohydrate Targets

In-race fueling sits on top of a daily intake foundation. The IAAF consensus statement and the joint ACSM/AND/Dietitians of Canada position stand both endorse periodizing total carbohydrate to training load.¹⁰¹¹

Day type	Carbohydrate target
Light or low-intensity training	3–5 g/kg/day
Moderate (~1 h/day)	5–7 g/kg/day
Endurance program, moderate-to-high intensity, 1–3 h/day	6–10 g/kg/day
Extreme commitment, 4–5+ h/day moderate-to-high intensity	8–12 g/kg/day

Periodized fueling (sometimes called "fuel for the work required") has replaced both "always high-carb" and ketogenic approaches. Burke's "Supernova" replication trials in elite race walkers showed the high-carb group improved their 10,000 m time by 4.8% (134 s), while the low-carb/high-fat group got 2.3% slower (−86 s). A periodized-carb group improved by 2.2% (61 s), though that middle result was a non-significant trend rather than a clear effect.¹² The verdict on ketogenic diets for competitive endurance performance is settled: they impair it.

"Train low, race high" still has a place. One or two easy aerobic sessions per week in a fasted or low-carb state (morning Zone 2 before breakfast, or a "sleep-low" pattern of hard PM session followed by low-carb dinner and fasted AM Z2) can support some adaptations. Never do this on quality, long, or high-intensity sessions.

Race-Day Protocols by Event

Event	Duration	Carbohydrate target
5K, criterium, sprint tri	< 45 min	Water only. A carb mouth-rinse may help.
10K, short TT, Olympic tri bike	45–75 min	~30 g/h or one gel mid-event.
Half-marathon, sportive, Olympic tri	75 min – 2 h	30–60 g/h. One carb-drink bottle plus 1–2 gels.
Marathon, gran fondo, half-Ironman	2–4 h	60–90 g/h. Sweet spot for most age-groupers.
Ironman, century, mountain marathon	4+ h	80–120 g/h depending on gut training.
Ultra (UTMB-style)	6+ h	60–90 g/h plus real food and savory items.

A pair of 2020 trials following elite runners through a mountain marathon found that 120 g/h lowered muscle damage markers (CK, LDH, GOT) at 24 hours and produced better 24-hour recovery of jump height, strength, and high-intensity run capacity than 60 or 90 g/h. Of the 26 athletes randomized, 6 did not finish the protocol: 3 withdrew with GI symptoms (reflux, flatulence) and 3 with injury.¹³ The high-intake ceiling is real, but so is the GI risk that comes with it.

Pre-Race Carb Loading

The modern protocol is 8–12 g/kg/day for 1–2 days before the race, with no depletion phase needed. For a 70 kg runner that is 560–840 g/day. The night-before-only pasta dinner is the most common amateur mistake: it is both too late and too concentrated. Expect a 2–4 lb gain, from the stored glycogen plus the water that accompanies it, conventionally estimated at around 3 g of water per gram of glycogen. (That ratio is textbook but not airtight; it comes from whole-body water measurements rather than any direct observation of water bound to glycogen.) The weight gain is the point, not a side effect.

Pre-race meal: 1–4 g/kg of low-fiber, familiar carbohydrate 1–4 hours before start. White bread or bagel with honey, white rice, oatmeal, banana, sports drink. Nothing new, nothing high-fiber.

Mid-Race Mechanics

• Cadence: Take something every 15–25 minutes. The gut empties best with consistent small doses, not big intermittent ones.
• Concentration: 6–8% carbohydrate solution (60–80 g/L). Above ~10% slows gastric emptying, unless you're using a hydrogel or a specifically formulated high-concentration product.
• Fluid: 500–1000 mL/h depending on sweat rate and conditions. Dehydration over 2% body mass impairs gastric emptying and amplifies GI symptoms.
• Sodium: 300–800 mg/h in most conditions, up to 1500 mg/h for heavy or salty sweaters and hot races.
• Caffeine: 3–6 mg/kg about 45–60 min pre-race, with small (~50–100 mg) maintenance doses every 1–2 hours in long events. Caffeine and carbohydrate are synergistic: caffeine modestly boosts intestinal carb absorption.

Gut Training: The 6–10 Week Protocol

The gut is an adaptable organ. Over 28 days, training with high carbohydrate availability raised the rate at which cyclists could oxidize ingested carbohydrate.¹⁴ Shorter blocks help too: two weeks of repeated gut challenges during running reduced malabsorption and GI symptoms.¹⁵

A practical ramp: start at 30 g/h during one or two long sessions per week, then add roughly 10 g/h each week. By weeks 6–7 you should be tolerating 80–90 g/h, and from week 8 onward you can push toward your race target (up to 120 g/h for the well-trained). The numbers are not sacred; the discipline of progressive, repeatable exposure is.

Rules:

• One or two key long sessions per week at race intake, not every ride or run.
• Pair every dose with adequate fluid (150–200 mL per 30 g carbohydrate).
• If GI symptoms appear, hold the previous step for another week before progressing.
• Use the exact products, ratios, and flavors you will race with.

Products: Gels, Drinks, Chews, Real Food, Hydrogels

Because the form of delivery does not change the physiology at a given dose,⁷ choose by practicality.

Format	Best for	Carbs per unit	Pros	Cons
Liquid drink mix (Skratch Super High-Carb, SiS Beta Fuel, Tailwind, Maurten 320, Precision PF 90)	Cycling, hot weather, athletes who can drink while running	60–100 g/bottle	Combines hydration, fuel, sodium; easy to titrate; gentle on stomach	Hard to consume at marathon pace; spillage; flavor fatigue
Gels (Maurten 100/160, SiS, GU, Precision PF 30, Neversecond)	Running, structured sessions, races needing precise timing	22–40 g/gel	Compact, precise dose, work at all intensities	Need water co-ingestion; concentrated osmolality can cause GI issues
Chews / blocks (Clif Bloks, Honey Stinger, SiS Beta Fuel chews)	Long bike rides, ultras, athletes who hate gels	4–10 g/chew	Chewing satisfaction; portion control; less concentrated	Slower to consume; require dental tolerance during exercise
Real food (banana, dates, rice cakes, sandwiches, gummy candy, sushi rice balls)	Ultras, long bike rides, multi-day events	Variable	Cheap; psychological variety; combats sweet fatigue	Variable absorption; fiber risk; harder to dose precisely
Hydrogel (Maurten)	Athletes pushing > 90 g/h with severe GI history; high-concentration delivery	Same dose, pectin/alginate matrix	Tolerated at higher concentrations; premium taste	Cost (3–4× cheaper alternatives); independent evidence weak

A practical mixing strategy for long events: use a drink mix as your hydration backbone (covers fluid, sodium, and ~30–60 g/h of carbohydrate), top up with gels every 30–45 minutes, and pre-position real food at aid stations or in special-needs bags for ultras. Keep at least 2 flavors and textures to fight palate fatigue after hour 3.

Hydrogels: Hype vs Evidence

Maurten markets its pectin/sodium-alginate hydrogel as encapsulating carbs to bypass GI distress and improve absorption. The independent peer-reviewed evidence is mostly null. McCubbin's Monash group ran 9 trained runners for 3 hours at 90 g/h and found the hydrogel changed nothing: not blood glucose, not malabsorption, not substrate oxidation, not GI symptoms, not time to exhaustion. Burke's group reached the same verdict with 19 elite race walkers over 26 km.¹⁶ One trial in sub-2:40 marathoners did find a hydrogel advantage in performance, oxidation, and GI tolerance at 90 g/h, so the effect may surface under some conditions and not others.¹⁷

The honest verdict: Maurten products deliver their carbohydrates well, but so do cheaper options from SiS, Precision Fuel & Hydration, Skratch, Neversecond, and Amacx. Buy on taste, texture, and convenience, not hydrogel claims alone.

Recovery: Carbs Lead, Protein Supports

Rapid recovery (under 8 hours to next session, twice-a-day or stage races):

• 1.0–1.2 g carbohydrate per kg body mass per hour for the first 4 hours.
• Start within 30 minutes of finishing.
• Use high-GI sources (white rice, white potato, sports drink, fruit juice, white bread).
• Add 20–40 g protein for muscle protein synthesis, not for glycogen.

Normal recovery (24+ hours to next session):

• Hit your daily carbohydrate target (3–12 g/kg depending on the day). Timing matters less than the total.
• Spread protein across 4–5 meals of 20–35 g each.

On protein co-ingestion the evidence points one way. When carbohydrate is already being fed at roughly 1 g/kg/h or more, adding protein does not further increase glycogen synthesis.¹⁸ Protein addition meaningfully boosts glycogen synthesis only when carb intake falls below about 0.8 g/kg/h, which can be useful when appetite or budget limits carb intake. Protein remains essential for muscle protein synthesis, just not as a glycogen lever.

Common Pitfalls

1. Race-day surprise. Trying a new gel, ratio, or product in a key race. Practice every fueling element in training first.
2. Carb-loading the night before only. Glycogen super-compensation needs 24–48 hours, not 12.
3. Underfueling Zone 2 long sessions. Doing every long session depleted compromises the next day's quality.
4. Over-fueling easy sessions. Three gels on a 60-minute Zone 2 jog is unnecessary and trains your gut to expect calories that don't match output.
5. Ignoring fluid co-ingestion. Concentrated carbohydrate without water = osmotic diarrhea. Each 30 g gel needs 150–200 mL water.
6. High-fiber pre-race meals. Save the salad for after the race.
7. Treating 120 g/h as a status symbol. No study has put age-group athletes head-to-head at 120 versus 80 g/h, so treat this as coaching judgment rather than settled science: given that even elite runners report their worst GI symptoms at 120 g/h, an untrained gut is likely to lose more to nausea than it gains from the extra carbohydrate. A well-tolerated 80 g/h beats an aspirational 120 g/h you spend the last hour regretting.
8. Ignoring caffeine + carbohydrate synergy. Use both together; they boost intestinal absorption.
9. Bonking from chronic underfueling. Glycogen-depleted athletes feel fine for 60–90 min, then collapse. Start fueling before you feel low.

Also worth knowing: in ultramarathons, GI distress is among the most common reasons athletes drop out, with nausea and vomiting leading the list. Jeukendrup's landmark long-distance triathlon study reported that 93% of the athletes experienced at least one GI symptom, 43% reported serious GI problems, and 7% abandoned the race because of them.¹⁹ A "perfect" fueling plan that wrecks your gut is worse than a conservative one you can execute under pressure.

Staged Recommendations

Tier 1 (all athletes, starting this week):

• Periodize daily intake: 3–5 g/kg on light days, 5–7 g/kg on moderate days, 6–10 g/kg on long or hard days.
• Match in-session fueling to intensity and duration.
• Any session over 75 minutes with intensity: take in at least 30 g/h of carbohydrate.
• After hard or long sessions, hit 1.0–1.2 g/kg of carbohydrate within the first hour, with 20–30 g of protein.

Tier 2 (athletes targeting a peak event in 3–6 months):

• Start a structured gut-training block 8–10 weeks out. Add 10 g/h every 1–2 weeks during one weekly long session until you hit your race target.
• Switch to glucose+fructose products in a 2:1 ratio (or 1:0.8 if targeting > 90 g/h).
• Practice carbohydrate loading (8–12 g/kg/day) during a tune-up race 4–6 weeks out, not race week for the first time.
• Test the full fueling and hydration plan in 2–3 race-simulation sessions.

Tier 3 (highly trained athletes targeting long events > 4 h):

• Consider working up to 100–120 g/h, but only after Tier 2 is solid.
• Adopt 1:0.8 or 1:1 glucose:fructose at these doses.
• Reassess if the event is under 4 hours or run-dominant; the marginal benefit shrinks fast.

Stop pushing intake higher if any of these are true:

• GI symptoms are consistently 4/10 or worse.
• Race duration is under 90 minutes.
• The event is mostly Zone 2 relative to your fitness.
• Training has more low-intensity than high-intensity work.

The pros are not wrong about 120 g/h — they are just answering a different question than most readers of this post are asking. Hit your daily carbohydrate target, match in-race intake to intensity and duration, train your gut, recover with carbs first, and you will outperform athletes who chase the headline number without the foundation underneath it.

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Footnotes

1. Podlogar T, quoted in Cotton J. "High-carb fueling has propelled the Tour de France to record speeds. Will it work for us, too?" Velo (2025). ↩︎ ↩︎

2. Ravikanti S, et al. "13C-labelled glucose-fructose show greater exogenous and whole-body carbohydrate oxidation and lower O2 cost of running at 120 versus 60 and 90 g/h in elite male marathoners." Journal of Applied Physiology (2025). ↩︎ ↩︎

3. Chambers ES, Bridge MW, Jones DA. "Carbohydrate sensing in the human mouth: effects on exercise performance and brain activity." The Journal of Physiology (2009). The earlier performance trial — Carter JM, Jeukendrup AE, Jones DA, "The effect of carbohydrate mouth rinse on 1-h cycle time trial performance," Medicine & Science in Sports & Exercise (2004) — found a significant performance improvement but explicitly no difference in heart rate or rating of perceived exertion. ↩︎

4. Wilson PB. "A narrative review of the high-carbohydrate fueling revolution (≥100 g/h) in the professional peloton." Sports Medicine (2025). ↩︎

5. Rothschild JA, et al. "Carbohydrate ingestion during prolonged exercise and net skeletal muscle glycogen utilization: a meta-analysis." Journal of Applied Physiology (2026). ↩︎

6. Jeukendrup A. "The optimal ratio of carbohydrates." MySportScience (2024). ↩︎

7. Hearris MA, 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). ↩︎ ↩︎

8. Brooks GA, Mercier J. "Balance of carbohydrate and lipid utilization during exercise: the 'crossover' concept." Journal of Applied Physiology (1994). ↩︎

9. San Millán I, Brooks GA. "Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals." Sports Medicine (2018). Crossover points are reported as a percentage of maximal power output on an incremental cycling test, not as a percentage of VO₂max. ↩︎

10. Burke LM, et al. "International Association of Athletics Federations Consensus Statement 2019: Nutrition for Athletics." International Journal of Sport Nutrition and Exercise Metabolism (2019). ↩︎

11. Thomas DT, Erdman KA, Burke LM. "Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance." Journal of the Academy of Nutrition and Dietetics (2016). ↩︎

12. Burke LM, et al. "Crisis of confidence averted: impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible." PLoS ONE (2020). ↩︎

13. Viribay A, et al. "Effects of 120 g/h of carbohydrates intake during a mountain marathon on exercise-induced muscle damage in elite runners." Nutrients (2020); and Urdampilleta A, Arribalzaga S, Viribay A, et al. "Effects of 120 vs. 60 and 90 g/h Carbohydrate Intake during a Trail Marathon on Neuromuscular Function and High Intensity Run Capacity Recovery." Nutrients (2020). Same cohort, two papers: the first reports the muscle damage markers, the second the neuromuscular recovery data. ↩︎

14. Cox GR, et al. "Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling." Journal of Applied Physiology (2010). ↩︎

15. Miall A, et al. "Two weeks of repetitive gut-challenge reduce exercise-associated gastrointestinal symptoms and malabsorption." Scandinavian Journal of Medicine & Science in Sports (2018). ↩︎

16. McCubbin AJ, Zhu A, Gaskell SK, Costa RJS. "Hydrogel carbohydrate-electrolyte beverage does not improve glucose availability, substrate oxidation, gastrointestinal symptoms or exercise performance, compared with a concentration and nutrient-matched placebo." International Journal of Sport Nutrition and Exercise Metabolism (2020); and King AJ, Rowe JT, Burke LM. "Carbohydrate Hydrogel Products Do Not Improve Performance or Gastrointestinal Distress During Moderate-Intensity Endurance Exercise." International Journal of Sport Nutrition and Exercise Metabolism (2020). ↩︎

17. Rowe JT, et al. "Glucose and fructose hydrogel enhances running performance, exogenous carbohydrate oxidation, and gastrointestinal tolerance." Medicine & Science in Sports & Exercise (2022; published online 2021). ↩︎

18. van Hall G, Shirreffs SM, Calbet JAL. "Muscle glycogen resynthesis during recovery from cycle exercise: no effect of additional protein ingestion." Journal of Applied Physiology (2000). Note the small sample (n = 5) and that carbohydrate was fed at approximately 1 g/kg/h. ↩︎

19. Jeukendrup AE, Vet-Joop K, Sturk A, et al. "Relationship between gastro-intestinal complaints and endotoxaemia, cytokine release and the acute-phase reaction during and after a long-distance triathlon in highly trained men." Clinical Science (2000). See also de Oliveira EP, Burini RC, Jeukendrup A, "Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations," Sports Medicine (2014), and Stuempfle KJ, Hoffman MD, "Gastrointestinal distress is common during a 161-km ultramarathon," Journal of Sports Sciences (2015), for the ultramarathon DNF data. ↩︎