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Consuming 90 to 120 g of carbohydrates per hour is the new trend in endurance sports, and cycling in particular, to achieve performance. But between gains of a few watts for pros and unknown effects on health, this overconsumption raises questions. Can you really ride faster by consuming more sugar without compromising your metabolism in the long term?
By Guillaume Judas – Photos: depositphotos.com
Lately, a new nutritional injunction has emerged in the world of endurance sports: consume 90 to 120 g of carbohydrates per hour during exercise to optimize performance. This approach comes in parallel with the increase in performance of high-level athletes, whether in cycling or running. Every year, records fall, surpassing those established during the great years of doping.
These results are inevitably questioned, especially since this trend is observed even in major sportives, or in ultra-endurance events. It gives pride of place to energy product brands that promise excellent results in the form of hyper-concentrated gels and other topettes with their optimized formulation and undeniable practicality, but sold at €120 per kg.
But this recommendation to consume so much sugar during exercise, often presented as revolutionary, raises questions. Is it suitable for everyone? What are its long-term health impacts? Shouldn’t amateur cyclists adopt a consistent and health-conscious dietary strategy?
A succession of nutritional dogmas over the years
Nutritional recommendations in endurance sports have often swung between extremes. In the 1980s, a diet with 70% slow carbohydrates (pasta, rice, semolina…) was popular. In major mass events (sportives, marathon and triathlon), the famous pasta party the night before was very widespread. This method consisted of consuming large quantities of starchy foods the night before a long-distance race in the hope of starting the next day with the maximum amount of glycogen (super fuel for effort) stored in the liver and muscles.
The Scandinavian dissociated diet was also in vogue for major objectives, alternating deprivation on the first days of the week and carbohydrate overload as the race approached.
In the 2010s, another trend emerged, on the contrary, with carbohydrate deprivation, close to the ketogenic diet. The objective of this type of diet is to stimulate fat burning (lipolysis) to preserve glycogen and push back the level of endurance. During certain training phases, athletes imposed long rides consuming only proteins and lipids (a bit like the deprivation period of the Scandinavian dissociated diet), reserving carbohydrate intake only for the race.
Fortunately, these dietary dogmas often end up being questioned in the face of physiological realities and long-term effects on physical… and mental health.
A questionable strategy
Since the beginning of the 2020s, another trend has emerged: the consumption of large quantities of carbohydrates just before, during, and just after exercise. Seeing professional riders freely helping themselves to large bags of sweets while getting on the bus just after the finish of a Tour de France stage is surprising, not long after the reign of Chris Froome and his salmon-avocado diet.
We can see it in this Remco Evenepoel YouTube video, where he talks about his meal before a time trial, in which he consumes… half a liter of Fanta (around 16 minutes)!
Recent studies (mostly observational), often relayed by the energy product industry, validate the consumption of 90 to 120 g of carbohydrates per hour. For example, Podlogar et al. (2021, Sports Medicine) show that these high intakes can improve performance during prolonged efforts by maintaining glycogen stores, but only in trained athletes who have accustomed their digestive system.
But these benefits are measured over short durations, without evaluating the long-term consequences on metabolic or cardiovascular health. To date, there are no studies on the long-term effects of this type of carbohydrate overload. Although the risks are mitigated by the context of sugar consumption during exercise, the health status of athletes who run on super fuel in a few years is unknown.
The risks of carbohydrate overconsumption
Consuming 90 to 120 g of carbohydrates per hour is almost like ingesting the equivalent of a liter of soda every 60 minutes (Stéphane Cascua, docdusport.com). During the last Tour de France, Kevin Vauquelin, 7th in the general classification, even revealed on the show Vélo Club that he had trained to absorb up to 150 g per hour. An extreme case not necessarily representative. But in elite athletes, such intakes can cause high blood glucose levels (1.8 to 2 g/L), close to diabetic thresholds (Stéphane Cascua, docdusport.com).
Repeated consumption of simple sugars (gels, energy drinks) can overload the digestive system, increasing the long-term risk of chronic disorders, such as irritable bowel syndrome or fructose sensitivity. According to Podlogar et al. (2021, Sports Medicine), absorbing so many carbohydrates requires prior digestive training, often inaccessible to amateurs, which increases these risks. Furthermore, an unbalanced diet, poor in antioxidants (vitamins, minerals), can induce oxidative stress and mild inflammation.
A 2020 study (Journal of Applied Physiology) also suggests that chronic high carbohydrate intake can reduce fat oxidation, creating a dependence on sugars, although varied training, such as fasted sessions, can limit this effect.
Products rich in simple sugars also expose teeth to an acidic environment, promoting enamel erosion and cavities. A 2019 study (Scandinavian Journal of Medicine & Science in Sports) shows an increased risk in endurance athletes, especially in cases of poor post-exercise oral hygiene.
Finally, excessive consumption of simple carbohydrates could, in theory, disrupt insulin sensitivity in the long term, particularly if the diet outside of exercise is also rich in sugars or if energy expenditure is insufficient. However, endurance athletes, who metabolize these carbohydrates during exercise, are less vulnerable than the general population.
Adapting carbohydrates to distance and intensity
For amateur riders, whose metabolism consumes fewer calories, a carbohydrate overload can cause immediate digestive problems (hence the need for a gradual increase in carbohydrate consumption and specific training as Kevin Vauquelin pointed out), and especially saturate the blood with glucose, thus increasing the risk of storage as fat. Gaining weight is not really the goal of amateurs who invest in health sports.
Physical activity, on the contrary, should be a powerful tool for preventing diabetes and cardiovascular diseases. By depleting muscle glycogen stores, training improves insulin sensitivity, facilitating glucose absorption at rest. This reduces the risk of type 2 diabetes, but on the condition of limiting carbohydrate consumption during and outside of exercise to a reasonable level.
At low intensity, the body learns to burn fat, releasing fatty acids and increasing “good” cholesterol (HDL). This adaptation protects arteries and optimizes the use of lipid reserves. A dietary strategy that promotes lipolysis, via fasted training or low carbohydrate intake, is therefore more sustainable and beneficial for health than massive sugar intakes.
For a demanding sportive, an intake of 40 to 60 g of carbohydrates per hour is sufficient to stabilize blood glucose and prevent a major bonk due to glycogen depletion. For a road cycling race, you can go up to 80 g, or even 90 g, especially on short and intense events, such as criteriums.
At a lower intensity but over longer efforts, such as ultra-endurance or long-distance gravel events, the body consumes more fat. Carbohydrates must be supplemented with digestible lipids and proteins (dried fruits, salted nuts, cheese, ham, biscuits, soup). This varied diet limits digestive problems, which are responsible, for example, for 50% of abandonments in ultra-endurance according to a study by the International Journal of Sports Medicine (2019).
A balanced approach to perform and stay healthy
The recommendation of 90 to 120 g of carbohydrates per hour, although supported by some studies, is unsuitable for the majority of athletes and potentially harmful in the long term, even if there is a lack of certainty on this subject. A reasoned strategy, based on a regular but not excessive intake of carbohydrates and a varied diet, optimizes performance while preserving health. Before doing like the pros, remember to gradually increase your training volume and intensity and adapt your nutritional strategy to the level of the events you participate in.
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