Former UTMB champion Karine Herry warns masters trail runners about the long-term health risks of copying elite 120 g/h carbohydrate fueling strategies.
The aid station tables at mountain ultras now look like science experiments. Elite runners grab precisely calculated flasks containing massive amounts of dissolved sugar. Amateurs watch these professionals closely and try to copy their exact nutrition plans on local trails. This dangerous disconnect between elite performance and everyday biology is exactly what former UTMB champion Karine Herry is now warning against.
Excessive carbohydrate intake in ultra-endurance fueling is the practice of consuming extremely high amounts of sugar during exercise without considering individual metabolic limits. Karine Herry won the UTMB in 2006. She was described as one of the pioneers of French ultra-trail racing. Herry now works as a physician in Haute-Loire.
In an interview reported by RMC Sport during the week of the 2026 Hoka UTMB Mont-Blanc, Herry voiced serious concerns. She said she was alarmed by recommendations that athletes consume 80 or 120 grams of sugar per hour. She questioned whether those figures actually fit normal human physiology. Herry specifically warned that the approach promoted by elite athletes could create problems for recreational athletes.
These everyday runners often imitate professional fueling practices without understanding the long-term risks. Carbohydrates remain a crucial energy source for endurance exercise. However, Herry objects to the idea that massive intakes are universally appropriate for all competitors. The modern focus on raw numerical targets can easily overshadow fundamental physiological reality.
The current trend toward aggressive fueling comes from the very top of professional sport. Marathon world-record holder Sabastian Sawe reportedly said he consumed 115 g/h during competition. Cyclist Tadej Pogačar was reported to consume approximately 120 to 140 g/h during a Tour de France stage. These examples describe elite athletes operating at absolute physiological extremes.
They should never be treated as baseline targets for ordinary trail runners. The science of carbohydrate absorption has evolved rapidly in recent years. Newer research shows that well-trained athletes can absorb more than the traditional limit of 90 grams per hour. This is achieved by consuming a specific blend of different carbohydrate types.
These different sugars utilize separate intestinal transport pathways. By using multiple metabolic pathways, the human body can process a higher total volume of energy. A review summarized by Tour Magazin highlights the performance benefits of these massive nutritional intakes. The review reports that an intake of 120 g/h may prevent the point at which the body shifts toward greater fat metabolism.
Consuming 45 or 90 g/h, by comparison, may only delay that inevitable metabolic shift. This makes massive carbohydrate consumption highly appealing to elite athletes racing near their absolute limits. However, human digestion has strict boundaries. The same Tour Magazin article notes that 90 to 120 g/h should be understood as a potential physiological maximum rather than a universal recommendation.
Reaching these astronomical numbers requires significant and progressive digestive training. It is not something an athlete can simply decide to do on race morning. Furthermore, the physical format of the fuel matters deeply when pushing these physiological limits. The reviewed research indicates that solid carbohydrate formats like bars produced more gastrointestinal discomfort than liquid, gel, or chewable alternatives.
Athletes consuming 120 g/h in one cited context experienced severe nausea and a lingering sense of fullness. These immediate physical rejections are warning signs from the body. They indicate that the digestive system is overwhelmed by the sheer volume of incoming calories. Your personal metabolic ceiling is unique to your own body.
Pushing past your digestive capacity causes immediate performance problems during an event. It can also create long-term risks for veteran athletes who blindly copy professional routines. Herry said she expected rapid negative consequences from aggressive sugar intakes. She warned that runners would quickly experience severe digestive problems on the trail.
Beyond the immediate discomfort, she also voiced clinical concerns regarding overall metabolic stability. She worried that chronic overconsumption might contribute to prediabetes or diabetes. She also expressed concern about inflammatory diseases and potential cancerous conditions. While Herry's warnings do not constitute clinical proof that race fueling directly causes these diseases, they highlight a critical tension for older runners.
Ambitious adults want to perform well while maintaining their health for decades to come. The underlying research driving these massive intake targets is rarely tailored to older demographics. Tour Magazin reports that more than 80% of examined studies involved recreational or young athletes. Fewer than 5% involved elite or world-class athletes.
Furthermore, fewer than 3% of the studies examined exclusively female participants. This creates massive uncertainty when applying elite-focused research directly to athletes aged 35 to 65. Masters runners must remember that a 50-year-old amateur has entirely different physiological needs than a professional cyclist in his twenties. Pace, terrain, and competitive goals vary wildly between amateur and professional ranks.
An aging body requires nuance, patience, and a deep respect for individual metabolic boundaries. Age alone does not determine an athlete's carbohydrate requirement. However, the available sources do not justify assuming that an older recreational ultrarunner should copy a world-class marathoner. Reendure encourages masters athletes to prioritize metabolic health over chasing a standardized hourly nutritional target.
You do not need to consume 120 grams of sugar per hour to successfully finish a long trail race. Current sports science guidance is moving toward a highly individualized nutritional model. The review summarized by Tour Magazin reports a graduated approach based strictly on event duration. Runners should target 30 to 60 g/h for efforts lasting 1 to 2.5 hours.
Athletes can safely increase to 60 to 90 g/h for efforts spanning 2.5 to 6 hours. Intakes up to 120 g/h are reserved exclusively for ultra-endurance efforts lasting more than 6 hours. Even then, these higher numbers are only appropriate for athletes who have thoroughly trained their digestive systems. Your fueling plan must also adapt to external variables and changing environmental conditions.
The same source reports that heat can reduce carbohydrate oxidation by 20 to 30%. Altitude above 4,000 metres can reduce it by a staggering 20 to 50%. A nutrition plan perfected on a cool, flat training run will likely fail during a hot, high-altitude mountain ultra. If you plan to increase your carbohydrate intake, you must test the strategy gradually in conditions that mimic your target race.
Small, incremental changes allow your gut to adapt over several weeks of rigorous training. You should closely monitor your body for persistent bloating, nausea, or cramping. These symptoms are clear evidence that your current nutrition strategy exceeds your digestive capacity. The correct plan is simply the highest intake you can consistently tolerate while maintaining your pace and enjoying the event.
It is never about hitting a prestigious number dictated by a professional athlete. Runners with existing metabolic concerns should discuss race fueling with a qualified clinician. Herry's medical warning makes this specialized consultation especially relevant for aging athletes.
Sustainable endurance fueling requires matching your nutritional intake to your actual biological capacity rather than chasing the extreme metrics of professional champions. Keep adapting.
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