Do You Really Need 120g of Carbohydrates per Hour?

Is 120g of carbohydrate per hour necessary for ultra performance? A balanced, evidence-based approach to fuelling your next ultra marathon.

For many, 2025 was the year of carbohydrates. Reports of extraordinarily high carbohydrate intakes circulated widely, not only in trail and ultra running, but across endurance sport. Joe Klecker, for example, has stated that he consumed 175 grams of carbohydrate per hour (g/h) at the New York Marathon and has experimented with intakes as high as 250 g/h in training [1].

Trail and ultra running have produced similar headlines. Precision Fuel and Hydration reported that Chris Myers averaged 126 g/h during his 14 hour 17 minute second-place finish at Western States [2]. Numbers that would have seemed extreme only a few years ago are now presented as necessary.

At the same time, nutrition brands have taken an increasingly visible role in the sport. It is difficult to watch a race broadcast, listen to a podcast, or follow a professional athlete without encountering sponsorship from companies such as The Feed, Precision Fuel and Hydration, Never Second, Näak or Maurten. I do not question the legitimacy of their products or the performances achieved with them however, when a single gel approaches $4-5 per serving [3], and carbohydrate targets climb ever higher, it becomes reasonable to ask where performance evidence ends and commercial incentive begins.

Yet the narrative is not uniform. Kilian Jornet reportedly averaged 86 g/h during his third-place performance at Western States [4]. Tom Evans won UTMB while consuming approximately 85-88 g/h [5]. Notably, this same post states that Evans had previously attempted to push intake towards 120 g/h, only to experience gastrointestinal distress that contributed to withdrawal in earlier races.

Kilian Jornet’s and Tom Evans’ intake still fall within what would traditionally be classified as “high carbohydrate” fuelling, but they are roughly 30% below the 120 g/h benchmark that is increasingly framed as the standard. So which story should athletes pay attention to? The 175 g/h marathon? The 120 g/h ultra? Or the 85 g/h UTMB win?

What Case Studies and Race Data Suggest

Before debating what athletes should consume, it makes sense to examine what they actually consume.

Because recent headlines focus almost exclusively on grams per hour, I will set aside carbohydrate type (glucose, fructose, maltodextrin) and oxidation ratios for now and focus purely on intake amounts.

One of the most informative datasets remains a 2011 study by Pfeiffer et al. [6]. In this study, 211 athletes (full and half Ironman, marathon and cycling events) completed a post-race questionnaire quantifying nutrient intake and rating 12 gastrointestinal (GI) symptoms on a scale from 0 (no problem) to 9 (worst ever experienced).

Average carbohydrate intake during competition was 62-71 g/h in full and half Ironman, 53 g/h in cycling events and 35 g/h in marathon runners. Carbohydrate intake did not differ significantly between full and half Ironman events however, the prevalence of serious GI symptoms was highest in full Ironman athletes (~31%), compared with half Ironman (14%), cycling (4%), marathon (4%) and professional athletes overall (7%). As expected, upper and lower GI symptom scores correlated with a prior history of GI distress.

Interestingly, in Ironman events, higher carbohydrate intake correlated with faster finishing times. It also correlated with increased nausea and flatulence. In other words, higher intake appeared performance-supportive but came at a physiological cost for some athletes.

Subjects characteristics and ambient conditions for all endurance events and nutrient intakes (mean ± SD). Source: Pfeiffer et al. [6]

Unfortunately, comparable large-scale, multi-sport studies are scarce. A more recent survey by Reinhard and Galloway [7] included over 1,000 German-speaking runners, triathletes and cyclists. Most were 18-39 years old, had over 10 years of experience, trained 5-14 hours per week, and were amateur or recreational athletes (2.3% identified as professional).

67.6% of respondents guided carbohydrate intake in training by “gut feeling” (pun not intended 😅), and only 21.6% actively monitored intake in grams per hour. Of those tracking intake, 52% consumed ≤60 g/h, while 48% consumed >60 g/h.

It is worth noting that over half of recreational participants reported general health and fitness as their primary goal. Even so, these results suggest that structured carbohydrate planning is uncommon. Whether actual intake aligns with current evidence-based recommendations remains unclear, particularly among those not using gram-per-hour calculations.

To gain a more current, race-focused perspective, I examined publicly available case studies from Precision Fuel & Hydration [8]. These are not peer-reviewed datasets and are inherently subject to commercial bias. Nonetheless, they provide a snapshot of reported fuelling practices among runners.

Upon visualising the data, it becomes clear that reported carbohydrate intake appears to have increased over the past four years, from ~70 g/h to ~80-90 g/h in both amateur and professional athletes however, data prior to 2023 are sparse, so the apparent upward trend may reflect sampling bias rather than a true shift in practice. Furthermore, although some athletes report >120 g/h, a substantial proportion still consume <60 g/h.

Data from case studies looking at carbohydrates consumed per hour during running events over time including trend line. Source: Precision Fuel & Hydration [8]

I initially assumed that lower intakes would cluster in shorter events but this assumption does not hold. While athletes in events under two hours consumed less carbohydrate (only four case studies), events lasting 2-24 hours averaged ~80 g/h. For events exceeding 24 hours, intake dipped to ~70 g/h, though this subgroup included only 12 case studies.

Data from case studies looking at carbohydrate intake per running race duration. Source: Precision Fuel & Hydration [8]

I also explored whether environmental conditions influenced intake. Minor differences were visible, but given small sample sizes, no strong relationship between weather and carbohydrate consumption could be identified.

Data from case studies looking at carbohydrate intake by race conditions. Source: Precision Fuel & Hydration [8]

A more controlled insight comes from a recent study by Lanpir et al. [9], which quantified planned, perceived and actual carbohydrate intake during a 101 km cycling race and a marathon. Sixty athletes participated (38 runners) in this study and researchers assessed intake via food diaries and pre- and post-race weighing of carbohydrate-containing products.

Actual in-race carbohydrate consumption was 16-17% lower than planned, with cyclists consuming an average of 49.1 g/h rather than their planned 58.9 g/h and runners consuming 21.7g/h compared to their planned 25.9 g/h. The discrepancy was largely attributed to leftover gel residue in sachets, with powders, sports drinks and gummies contributing minimally to the gap. Marathon runners overestimated intake more than cyclists, though it is unclear whether this reflects product choice (greater reliance on gels) or sample size limitations.

Comparison of planned, perceived, and actual carbohydrate (CHO) intake during races among marathoners and cyclists. Source: Lanpir et al. [9]

Several additional points are also worth highlighting. Firstly, absolute intake, particularly in runners, was low relative to recommendations. Second, athletes failed to reach even their modest targets by a meaningful margin. Third, perceived intake exceeded actual intake.

This last point is very important, since if athletes believe they consumed sufficient carbohydrate, they are unlikely to attribute suboptimal performance to under-fuelling. Taken together, this is a practical warning. A nutrition plan is not sufficient, and execution and training matters. Therefore athletes should look to practise fuelling under race-like conditions, verify that products are fully consumed, consider formats that are easier to ingest completely and account for potential under-consumption (approximately 15% in gel-based strategies).

Foods and drinks consumed during the race. Source: Lanpir et al. [9]

Why More is Better

If many amateur athletes consume 25-60 g/h, why are professionals experimenting with 90, 120 or even higher intakes? What are the benefits or ingesting more carbohydrates?

A study published in 2025 compared 60 g/h (maltodextrin:fructose 1:0), 90 g/h (2:1) and 120 g/h (1:1) during a two-hour treadmill protocol in eight well-trained runners (mean marathon personal best ~2:23) [10]. Carbohydrate was administered every 15 minutes via bottles while researchers assessed exogenous carbohydrate oxidation and gastrointestinal (GI) symptoms.

After two hours, carbohydrate oxidation was highest in the 120 g/h condition. Because carbohydrate yields more energy per litre of oxygen consumed than fat, greater carbohydrate utilisation theoretically improves running economy. In this study, oxygen cost of running was lower in the 120 g/h condition when compared with 90 and 60 g/h. The authors therefore concluded that ingesting 120 g/h in a 1:1 maltodextrin:fructose ratio reduced oxygen cost relative to lower intakes. It remains unclear whether this effect was driven by total dose, the glucose-fructose ratio, or both.

The test protocol of Ravikanti et al. Source: Ravikanti et al. [10]

Two subsequent studies from the same research group tested a similar hypothesis during a 42 km mountain marathon with ~2,000 m of ascent (for a total of ~4,000 m total elevation change) [11, 12]. Twenty-six elite trail runners were randomised to consume 60, 90 or 120 g/h during the race. Six athletes withdrew (three due to GI issues, three due to injury), leaving 20 finishers for analysis.

In the first study [11], researchers assessed internal exercise load and neuromuscular function via jump tests, squat tests and an aerobic power-capacity test at baseline and 24 hours post-race. Significant declines in neuromuscular performance were observed in the 60 g/h and 90 g/h groups, but not in the 120 g/h group. Internal exercise load (calculated using individualised training impulse (TRIMP)) was also significantly lower in the 120 g/h condition (314.8 ±16.2 compared to 371.2 ±16.2 for 90 g/h and 399.8 ±17.5 for 60g/h). The authors concluded that consuming 120 g/h may attenuate neuromuscular fatigue and improve recovery of high-intensity running capacity 24 hours after a demanding mountain marathon.

The test protocol of Otegui et al. Source: Otegui et al. [11]

The second study [12] examined internal load (calculated using session RPE (sRPE) of mountain marathon duration × RPE) and biochemical markers of exercise-induced muscle damage, including creatine kinase (CK), lactate dehydrogenase (LDH), glutamic oxaloacetic transaminase (GOT), urea and creatinine. Internal exercise load was significantly lower in the 120 g/h group (3805 ± 281) compared with 60 g/h (4688 ± 705) and 90 g/h (4692 ± 716). Markers of muscle damage were also lower in the 120 g/h condition. The authors concluded that high carbohydrate intake during a mountain marathon may reduce perceived exertion and reduce muscle damage.

To place these findings in a broader context, I reviewed a 2021 systematic review examining carbohydrate intake during one-day ultra trail races [13]. Notably, the only two 120 g/h studies available at the time were [11] and [12], which I have already discussed separately.

Several consistent themes emerged from the review:

• Ultra runners typically consumed less carbohydrate than recommended, regardless of whether a sports dietitian was involved or not.

• International consensus guidelines recommend up to 90 g/h for exercise exceeding three hours, particularly when using multiple transportable carbohydrates (e.g. glucose plus fructose).

• Combining glucose and fructose increases carbohydrate oxidation compared with glucose alone and is associated with improved performance.

• Oxidation rates were similar whether carbohydrates were delivered in liquid or solid form.

• Gut training was repeatedly highlighted as necessary to tolerate higher intake rates.

• Muscle glycogen depletion remains a key performance limiter in ultra endurance events, and maintaining carbohydrate availability may support both performance and subsequent recovery.

Taken together, this body of evidence supports the idea that higher carbohydrate intake, particularly using glucose-fructose combinations, can increase oxidation rates, reduce physiological strain and potentially improve recovery in demanding endurance events.

However, these findings do not imply that intake should be pushed indefinitely upward. Ultra endurance athletes often assume that if some is good, more must be better. The literature suggests benefits to higher intake, but it also indicates clear physiological constraints.

Why More is Worse

If higher carbohydrate intake can improve oxidation rates and reduce internal load, why not simply push intake as high as possible? One immediate constraint is gastrointestinal (GI) tolerance.

In a 2022 survey by the American Trail Running Association [14], 20% of athletes who recorded a DNF reported that illness, typically gastrointestinal, was the primary cause. This was the third most common reason for non-completion, behind injury (27%) and missing cut-offs (24%). GI distress is therefore not just an inconvenience, it can also be race-ending.

Even in the controlled laboratory setting of study [10], where 120 g/h reduced oxygen cost compared with lower doses, the incidence of moderate or severe (≥4) GI symptoms was high across all conditions however, scores for nausea, stomach fullness and abdominal cramps were highest in the 120 g/h group. In other words, the condition that improved running economy also produced the greatest incidence of GI distress.

Gastrointestinal symptom progression during exercise in the 60 (A), 90 (B), and 120 g/h (C) trials during prolonged treadmill running. Source: Ravikanti et al. [10]

The mountain marathon studies [11, 12] reported less detail regarding GI outcomes. Of the 26 athletes initially enrolled, six withdrew: three due to GI issues and three due to injury. The distribution of GI-related withdrawals across the 60, 90 and 120 g/h groups was not specified. While 120 g/h was associated with lower internal load and muscle damage among finishers, we do not know whether higher intake increased the likelihood of non-completion.

The 2021 systematic review [13] dedicates substantial attention to GI complications. It concludes that gastrointestinal symptoms are common in endurance athletes and frequently impair performance and recovery. GI distress is also one of the main reasons athletes fail to meet carbohydrate intake recommendations during competition.

However, the review highlights several complexities.

First, GI distress is multifactorial. Carbohydrate dose matters, but so does timing. Large boluses consumed over a short period may increase symptom risk. Hydration status plays a role, and dehydration independently increases GI strain. It is therefore overly simplistic to claim that “more carbohydrate equals more GI issues”.

Second, findings across studies are inconsistent. Some report that faster athletes experience more GI symptoms while other studies suggest the opposite. Study designs vary considerably, making direct comparison difficult.

Third, carbohydrate source and format differ widely across studies. Some use gels, others sports drinks, powders, energy bars or even solid foods such as sandwiches. One study reported cola consumption without specifying quantity or type of cola drink and whether it was carbonated or not. Without standardisation of carbohydrate type, concentration and co-ingested nutrients, it is difficult to isolate the effect of dose alone.

Finally, pre-race dietary intake may influence race-day tolerance. Macronutrient composition in the 24-48 hours preceding competition can alter gut function and substrate availability, yet this variable is not always controlled.

Despite these inconsistencies, one recommendation is consistent across the literature: gut training matters. Repeated exposure to higher carbohydrate intakes during training appears to improve tolerance and absorption capacity. Testing race nutrition under realistic conditions remains the most practical strategy for reducing the risk of GI-related performance impairment.

This brings us to an interesting crossroads. Higher carbohydrate intake may reduce physiological strain and support performance, but only if it can be tolerated and consistently executed. What should you do?

A Realistic Nutritional Plan

Nutrition is not optional in ultra marathon racing. Even the fastest athletes require at least three hours to complete an ultra distance event, and beyond that duration, carbohydrate availability becomes performance-relevant. In longer races, fuelling becomes a central component to success.

Because of this, your approach must be deliberate. A nutrition strategy should go beyond “eat X grams per hour”. It should account for terrain, climbing and descending, weather conditions, altitude, aid station access and time of day. Tom Evans’ UTMB strategy is a useful example [5], since intake was structured around race demands rather than treated as a static hourly number.

How Much Carbohydrate per Hour?

The 2019 International Society of Sports Nutrition position stand [15] recommends 30–50 g/h of carbohydrate and 5–10 g/h of protein from calorie-dense sources during prolonged exercise. In light of more recent evidence, this lower range likely underestimates what most ultra runners can benefit from.

Based on the literature discussed:

• <45 g/h likely limits performance in most athletes by failing to adequately support carbohydrate availability.

• 60–90 g/h represents a practical and evidence-supported range for the majority of well-trained ultra runners.

• 90 g/h may confer incremental benefits in specific contexts, but tolerance becomes increasingly individual and risk of GI disturbance rises.

Importantly, the Lanpir et al. study [9] showed that athletes under-consumed relative to plan by 16-17%. This has practical implications, since if your physiological “floor” is ~45 g/h, planning for 50 g/h may result in unintentionally dropping below that threshold. For this reason, 60 g/h represents a sensible minimum target for most performance-focused athletes, providing a margin against potential execution error.

The 60–90 g/h range aligns with current consensus recommendations for events exceeding three hours when using glucose-fructose combinations. It is high enough to meaningfully support oxidation and glycogen sparing, yet moderate enough to remain achievable with appropriate gut training.

Should You Aim for 120 g/h?

The controlled studies suggest potential advantages at 120 g/h: reduced oxygen cost, lower internal load and attenuated markers of muscle damage. However, these benefits were observed in small samples of highly trained athletes under specific conditions. Real-world tolerance varies substantially.

The potential performance gain beyond 90 g/h appears incremental, while the potential downside, race-compromising GI distress, is substantial. In my opinion, the risk-reward ratio above 90 g/h is not clearly favourable for most sub-elite and everyday athletes.

That does not mean 120 g/h is inappropriate. It means it should be justified, tested extensively, and tailored to the individual rather than adopted because it is fashionable.

Your Task for 2026

If there is a practical takeaway from this discussion, it is this:

1. Audit your actual nutritional intake during training.

2. Establish a structured hourly target within the 60-90 g/h range.

3. Work towards your target during training, increasing from your current intake by as little as 5 g/h at a time.

4. Monitor GI symptoms and adapt as necessary.

5. Refine composition, timing and format based on data.

For my next article I will publish an article about gut training and how to build an individualised race nutrition plan, so make sure you subscribe to get the next instalment of this series right in your inbox.

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While everybody has spent 2025 increasing their carbohydrate intake, Marco Altini spent his year improving his metabolic flexibility and fat oxidation through periodised nutrition. Although he agrees that carbohydrate availability is essential for performance and recovery, his approach challenges the assumption that simply increasing carbohydrate intake is always the primary lever for improvement.

Listen to this podcast episode on Substack, as well as on YouTube, Spotify, Apple Podcasts and YouTube Music.

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