{"id":1290,"date":"2026-02-03T08:21:00","date_gmt":"2026-02-03T07:21:00","guid":{"rendered":"https:\/\/www.nutrimedia.info\/?post_type=news&#038;p=1290"},"modified":"2026-01-28T21:40:19","modified_gmt":"2026-01-28T20:40:19","slug":"carbo-loading-fatigue-endurance","status":"publish","type":"news","link":"https:\/\/www.nutrimedia.info\/en\/news\/carbo-loading-fatigue-endurance\/","title":{"rendered":"Carbo-loading: what if we've been aiming at the wrong target for 60 years?"},"content":{"rendered":"<p><strong>A major review published in January 2026 in Endocrine Reviews challenges the dogma of muscle glycogen and carbo-loading. It is not the depletion of reserves that causes endurance fatigue, but the inability to maintain stable blood sugar levels. A paradigm shift that could transform the way endurance athletes eat.<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>The dogma: fill the tank before the race<\/strong><\/h2>\n\n\n\n<p>Since the Scandinavian studies of the 1960s, sports nutrition has been based on a simple equation: <strong>the more muscle glycogen you store before the event, the longer you'll last.<\/strong> Hence the pre-marathon pasta parties and the recommendations of 60-90 grams of carbohydrate per hour during the race.<\/p>\n\n\n\n<p>The muscle would be a reservoir to be filled. The \u00abmarathon wall\u00bb? An empty tank. This vision has shaped decades of products - gels, drinks, bars - all calibrated to maximise carbohydrate intake through carbo-loading.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Proofreading: it's not the muscle, it's the brain<\/strong><\/h2>\n\n\n\n<p>The review published in Endocrine Reviews - more than 100 years of data under the microscope - is the first of its kind in the world. <strong>tells a different story.<\/strong><\/p>\n\n\n\n<p>By re-analysing the original studies, the authors found that the subjects who collapsed at the end of the test not only had low muscle reserves. They also showed marked falls in <a href=\"https:\/\/www.nutrimedia.info\/en\/news\/sugar-and-brains-the-hidden-bill\/\" data-type=\"news\" data-id=\"1231\">blood sugar<\/a> - blood sugar levels. And that's where it gets interesting.<\/p>\n\n\n\n<p><strong>Unlike muscles, the brain cannot function without glucose. <\/strong>When blood glucose levels fall beyond a certain threshold - known as exercise-induced hypoglycaemia (EIH) - the central nervous system triggers a protective response: reduced motor signal, increased sensation of fatigue, subjective inability to maintain intensity.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>In other words: it's not the muscle that fails, it's the brain that pulls the handbrake to protect itself. And this even though muscle glycogen reserves are not necessarily depleted.<\/p>\n<\/blockquote>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<iframe loading=\"lazy\" title=\"Carbo-loading in question\" width=\"1080\" height=\"608\" src=\"https:\/\/www.youtube.com\/embed\/4Qf6g-lAiBE?feature=oembed\"  allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe>\n<\/div><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>The liver, an underestimated key player<\/strong><\/h2>\n\n\n\n<p>If the brain depends on blood glucose, where does this glucose come from during exercise? P<strong>The main source of glucose is the liver, which releases its own glycogen reserves and manufactures glucose from other substrates (gluconeogenesis).<\/strong><\/p>\n\n\n\n<p>The problem is that the liver stores only 50 to 100 grams of glycogen - far less than the muscles. And if its production no longer keeps pace with demand, blood sugar levels fall.<\/p>\n\n\n\n<p>The authors of the review argue that it is this liver failure - and not the depletion of muscle stores - that constitutes the real bottleneck in endurance performance. <strong>Protecting blood sugar levels then becomes the priority objective, rather than filling up the muscles.<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Is 10 grams per hour enough?<\/strong><\/h2>\n\n\n\n<p>This is the data that is the subject of most debate. A randomised crossover trial carried out on competitive triathletes tested the effect of a minimum intake of 10 grams of carbohydrate per hour during an endurance test.<\/p>\n\n\n\n<p><strong>Result: time to exhaustion increased by 22 %. Above all, exercise-induced hypoglycaemia disappeared - in both groups, whether they were on a high-carbohydrate or low-carbohydrate diet on a daily basis.<\/strong><\/p>\n\n\n\n<p>Ten grams per hour is a far cry from the 60 to 90 grams recommended by current guidelines and carbo-loading. That's barely half an energy gel. And yet.., <strong>this is enough to maintain blood sugar levels and stave off fatigue.<\/strong><\/p>\n\n\n\n<p>The authors of the review are not saying that high intakes are unnecessary. But they question their systematic necessity and their cost-benefit ratio - particularly in terms of digestive tolerance, a recurring problem among ultra-endurance athletes who try to absorb 90 to 120 grams of carbohydrate per hour.<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"572\" src=\"https:\/\/www.nutrimedia.info\/wp-content\/uploads\/2026\/01\/carbo-loading-et-mythe-de-leffort-1024x572.jpg\" alt=\"\" class=\"wp-image-1292\" srcset=\"https:\/\/www.nutrimedia.info\/wp-content\/uploads\/2026\/01\/carbo-loading-et-mythe-de-leffort-980x547.jpg 980w, https:\/\/www.nutrimedia.info\/wp-content\/uploads\/2026\/01\/carbo-loading-et-mythe-de-leffort-480x268.jpg 480w\" sizes=\"(min-width: 0px) and (max-width: 480px) 480px, (min-width: 481px) and (max-width: 980px) 980px, (min-width: 981px) 1024px, 100vw\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Low-carb and performance: reconciling the two?<\/strong><\/h2>\n\n\n\n<p>The study on triathletes provides another piece of information. After four weeks of adaptation <strong>on a very low-carbohydrate diet (less than 50g\/day), endurance performance was comparable to that obtained on a high-carbohydrate diet<\/strong> - provided that this minimum supplement of 10 g\/h is provided during exercise.<\/p>\n\n\n\n<p>Keto-adapted\u00ab athletes develop remarkable fat oxidation capacities - in excess of 1.5 g\/min, even at high intensity. This does not mean that the low-carb diet is superior. <strong>But absolute dependence on carbohydrates during exercise is less rigid than previously thought.<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What this means for sportspeople<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Less pressure on pre-competition carbo-loading.<\/strong> Replenishing your reserves is still useful, but it may not be the limiting factor we thought.<\/li>\n\n\n\n<li><strong>More modest and better tolerated intakes during exercise.<\/strong> Rather than forcing 60-90 g\/h - with the digestive problems that entails - a regular intake of 10-20 g\/h could maintain blood sugar levels without overloading the digestive system.<\/li>\n\n\n\n<li><strong>A new focus on blood sugar levels.<\/strong> Continuous glucose sensors could become management tools - aiming for glycaemic stability rather than maximising intake.<\/li>\n\n\n\n<li><strong>A place for low-carb strategies.<\/strong> Athletes who prefer a low-carbohydrate diet are not condemned to under-performance, as long as they keep their intake to a minimum during exercise.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What we don't know yet<\/strong><\/h2>\n\n\n\n<p>The review proposes a change of interpretative framework, but interventional studies remain limited. The trial on triathletes involved a small sample.<\/p>\n\n\n\n<p><strong>The classic recommendations (30-90 g\/h) are not out of the blue: they work for many athletes. The challenge is not to abandon them, but to understand when lower intakes may be sufficient.<\/strong><\/p>\n\n\n\n<p>The question of intensity remains open. At very high intensities, fat oxidation does not fully compensate for carbohydrate demand. The high recommendations are probably still relevant for short, intense efforts.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>The debate on carbo-loading has only just begun<\/strong><\/h2>\n\n\n\n<p>What's at stake here goes beyond the question of grams of carbohydrate per hour. It's about challenging the mental model that has dominated for the past 60 years: moving from \u00abmuscle-reservoir\u00bb to \u00abblood sugar-brain protector\u00bb.<\/p>\n\n\n\n<p>The data is solid but still patchy. One thing is certain: the debate on carbo-loading has been relaunched, and the next generation of recommendations is unlikely to resemble the previous one.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>FAQ<\/strong><\/h2>\n\n\n\n<p><strong>Has carbo-loading become unnecessary?<\/strong> No. The review does not recommend abandoning carbohydrate supercompensation, but suggests that fatigue is linked more to falling blood sugar levels than to muscle glycogen depletion. Pre-competition strategies can be reconsidered, not abandoned.<\/p>\n\n\n\n<p><strong>Are 10g of carbohydrates per hour really enough?<\/strong> In the study cited, yes - for triathletes tested to exhaustion. But the classic recommendations (30-90 g\/h) remain relevant for certain intensities, durations and athlete profiles. The optimum intake depends on the context.<\/p>\n\n\n\n<p><strong>Do low-carb diets harm endurance performance?<\/strong> After adaptation (around 4 weeks), endurance performance can be maintained on a low-carbohydrate diet, as long as minimal carbohydrate intake is provided during exercise. Keto-adapted athletes develop a strong capacity for fat oxidation.<\/p>\n\n\n\n<p><strong>How can I tell if I'm hypoglycaemic during exercise?<\/strong> Typical symptoms include sudden and disproportionate fatigue, difficulty concentrating, trembling and a feeling of weakness. Continuous glucose sensors allow objective monitoring, but are still not accessible to most amateurs.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Sources<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Noakes T. et al. Carbohydrate Ingestion on Exercise Metabolism and Physical Performance. <em>Endocrine Reviews<\/em>, January 2026.<a href=\"https:\/\/academic.oup.com\/edrv\/advance-article\/doi\/10.1210\/endrev\/bnaf038\/8432248\" target=\"_blank\" rel=\"noreferrer noopener\"> academic.oup.com<\/a><\/li>\n\n\n\n<li>Prins P.J. et al. Carbohydrate ingestion eliminates hypoglycemia and improves time to exhaustion in triathletes. 2025.<a href=\"https:\/\/pubmed.ncbi.nlm.nih.gov\/39786965\/\" target=\"_blank\" rel=\"noreferrer noopener\"> pubmed.ncbi.nlm.nih.gov<\/a><\/li>\n\n\n\n<li>Gatorade Sports Science Institute - Dietary Carbohydrate and the Endurance Athlete.<a href=\"https:\/\/www.gssiweb.org\/research\/article\/dietary-carbohydrate-and-the-endurance-athlete-contemporary-perspectives\" target=\"_blank\" rel=\"noreferrer noopener\"> gssiweb.org<\/a><\/li>\n<\/ul>\n\n\n\n<p><strong>Are you interested in this subject?<\/strong><\/p>\n\n\n\n<p>\u2192 <strong>Do you have a specific question?<\/strong> Our AI assistant can give you quick guidance:<a href=\"https:\/\/www.nutrimedia.info\/en\/nutrimedia-offers-and-packs\/#chat-avec-nutrimedia\" data-type=\"link\" data-id=\"https:\/\/www.nutrimedia.info\/offres-et-packs-nutrimedia\/#chat-avec-nutrimedia\">Talking to the assistant<\/a><\/p>\n\n\n\n<p>\u2192 <strong>Need structured support?<\/strong> Find out more about our formats - from one-shots to editorial partnerships:<a href=\"https:\/\/www.nutrimedia.info\/en\/nutrimedia-offers-and-packs\/\"> See the offers<\/a><\/p>\n\n\n\n<p>\u2192 <strong>Would you like to discuss it in person?<\/strong> 30 minutes to define your needs, with no obligation:<a href=\"https:\/\/calendly.com\/nicolas-nutrimedia\/30min\" target=\"_blank\" rel=\"noopener\"> Reserve a slot<\/a><\/p>","protected":false},"template":"","meta":{"_acf_changed":false,"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","inline_featured_image":false},"class_list":["post-1290","news","type-news","status-publish","hentry"],"acf":[],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.nutrimedia.info\/en\/wp-json\/wp\/v2\/news\/1290","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.nutrimedia.info\/en\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.nutrimedia.info\/en\/wp-json\/wp\/v2\/types\/news"}],"wp:attachment":[{"href":"https:\/\/www.nutrimedia.info\/en\/wp-json\/wp\/v2\/media?parent=1290"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}