Illustration: Maria Chimishkyan

Test Gym

Carbo-Loading is Dead. Long Live Carbs!

What the science now says about housing pasta for peak athletic performance

Christie Aschwanden
Published in
7 min readFeb 5, 2020

Test Gym is a new Elemental column about the science of exercise.

WWhen I was a high school cross-country runner a few decades ago, my team would gather for dinner the night before meets to load up on pasta and bread. We were taught that “carbo-loading,” as this pre-race feasting on carbohydrate-rich foods was called, would help us perform our best the following day.

The concept of carbo-loading arose from research done in the 1960s by Scandinavian scientists using needle biopsies to peek at what was happening in muscles. In this study, which made a splash after it was published in Nature in 1966, researchers Jonas Bergström and Eric Hultman used themselves as the sole test subjects to measure what happened to the stores of glycogen (sugar used to fuel exercise) in their leg muscles before and after an intense one-legged session on a cycling ergometer.

They found that immediately after the bout of hard exercise, muscle glycogen levels plummeted in the leg that had done the work, while glycogen levels in the other leg remained stable. Over the next three days, the men ate a high-carbohydrate diet and the glycogen levels in their exercised leg soared to about twice the amount in the unexercised leg. This led to the idea that depleting a muscle’s glycogen levels and then feeding them with a high-carb diet could lead to a “supercompensation” effect that packed your muscles with extra fuel. Carbo-loading was born.

At the 1969 European Marathon Championships, British runner Ron Hill posted a spectacular come-from-behind win and attributed it to the concept, which he claimed prevented him from slowing down like the runner he overtook.

Indeed, the benefit of carbo-loading, as understood at that point, wasn’t so much that it could make you run faster, but that it could help you run at your optimal pace for longer, says Louise Burke, chief of nutrition strategy at the Australian Institute of Sport.

And while it was believed that optimal carbo-loading required a depletion phase where you tried to drain the glycogen stores with exercise and carb…



Christie Aschwanden

Author of GOOD TO GO: What the Athlete in All of Us Can Learn from the Strange Science of Recovery (Norton, 2019). Twitter: @CragCrest

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