Why Endurance Athletes Are Scarfing Up More Carbs Than Ever

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After the 2022 Tour of Flanders, a photo circulated on social media showing a detailed nutrition plan carefully taped to race winner Mathieu van der Poels handlebars. Some hard math indicated that the Dutchman took in more than 100 grams of carbohydrate per hour while winning the 169-mile race in just over six hours in an impressive digestive feat, as the conventional sports nutrition guidelines say that our ability to absorb carbs tops out at about 90 grams per hour.

To outsiders, van der Poels’ mega-carb intake seems like an isolated novelty. But in the year and a half since then, very high carbohydrate doses have become an emerging trend among elite athletes. New science suggests that it’s actually possible to consume up to 120 grams of carbohydrate per hour, and some pros have reportedly gone even higher than that. The unanswered question, for now, is whether it makes you faster.

The latest study to address the issue was published in Journal of Applied Physiology by a research team led by Robert Jacobs of the University of Colorado Colorado Springs. Jacobs and his colleagues use real-world data to simulate the range of physiological characteristics seen in elite marathon runners and calculate how much carbohydrate they’ll need to successfully run a sub-two- hour marathon.

If you’re fit, tapered, and properly carb-loaded, you already have a large supply of carbohydrates when you start a marathon, mainly stored as glycogen in your liver and muscles. The exact amounts depend on various factors including the size of your liver and legs, but on average researchers estimate that elite male marathoners start with 690 grams of glycogen and female marathoners starts at 499 grams.

At first glance, this seems promising, since they calculated that a two-hour marathon should require 612 grams of carbohydrate for elite men and (since women are smaller on average) 528 grams for women. . The problem is that you can’t remove the tank completely, for various reasons. One is that running doesn’t use every single muscle in your legs equally, so unused muscle fibers will still have some stored glycogen when you hit the wall. In general, you can use up about 62 percent of your stored carbohydrates during a two-hour marathon, leaving a large deficit that you need to fill by drinking or eating more carbs.

To make the numbers work for a two-hour marathon, Jacobs and his colleagues calculated that an average elite male marathoner would need to consume 93 grams of carbohydrate per hour, while an average woman would need 108 grams per times higher than the 90-gram max in current sports nutrition guidelines.

It’s an interesting review, though it’s worth acknowledging that it puts the cart (what wed like run) before the horse (what is really capable). We could run a similar calculation of how many carbs we would need to run back-to-back marathons in four hours, and that calculation would yield an astronomically high number, but the number has no real meaning in the world. Endurance limits depend on more than carbohydrate supply.

Still, Jacobs offers three arguments for why the two-hour marathon number is worth taking seriously. One is that recent lab studies have shown that humans are, in fact, capable of burning more than 90 grams of exogenous (meaning from drinks or food rather than internal storage) carbohydrates. every hour. For example, a study published last year by Tim Podlogar, an exercise physiologist at the University of Birmingham and nutritionist for the Bora-Hansgrohe pro cycling team, fed cyclists 120 grams of carbohydrate per hour and found that they is capable of burning more than 90 grams per hour. (The rest will be released or stored for later use.) Reaching this level of carb burn involves consuming a mixture of glucose and fructose in a ratio of 1:0.8, a change from the usual ratio of 1:0.5 in many current sports drinks and gels.

The second argument is that the digestive system can adapt. Sure, if you try to feed a group of volunteers 120 grams of carbohydrate per hour, their stomachs will rebel and you’ll conclude that it’s impossible to absorb that much. But try training your gut for a few months, like the Mathieu van der Poels of the world did, and who knows what you’re capable of?

The third argument is anecdotal: many high-speed athletes in sports such as cycling, triathlon, and running are reported to exceed 90 grams per hour. Velos Jim Cotton had a fantastic article in October about the carbohydrate revolution in cycling. There has been a big change in energy intake in the last five or six years, Ineos Grenadiers nutritionist Aitor Viribay Morales told Cotton. This is one of the biggest reasons why cyclists produce so much power, for so long, and how they do it every day.

Let’s agree, then, that moving the goalposts from 90 to 120 grams per minute is plausible. But there are reasons to be cautious before jumping on the bandwagon. For one thing, elite endurance athletes can burn carbohydrates faster, and for longer periods of time, than the rest of us. One reason why previous studies concluded that people could not burn more than 90 grams per hour is likely that the subjects were only well trained rather than elite.

Even if you can absorb 120 grams per hour, it may not make you faster. In the Podlogars study, cyclists burned more exogenous carbs when they consumed 120 instead of 90 grams per hour, but this did not reduce their rate of endogenous carb-burning that is, they still deplete the glycogen stores in their muscles just as quickly. Other studies have noted the same effect, and some studies have found that consuming higher levels of carbohydrate actually suppresses fat burning so effectively that you burn your internal carbohydrate stores instead. faster than you would, which is exactly the opposite. of your expectations.

As it happens, Sports and Exercise Medicine and Science They just published an academic debate called Contrasting Perspectives on whether ketogenic diets are beneficial for athletic performance. Arguing the pro-keto case is Tim Noakes; Arguing are Louise Burke and Jamie Whitfield of the Australian Catholic University, who led a series of studies on ketogenic diets in elite racewalkers. I wrote about some of Burke and Whitfields results here, and I won’t repeat that whole discussion. My overall take remains the same as it was: keto for endurance is a sound idea in theory, but when you actually test the performance it doesn’t live up to the hype.

What’s interesting is that despite the title Ketogenic Diets Are Beneficial for Athletic Performance Noakess pro-keto case doesn’t spend much time arguing that ketogenic diets enhance performance. Instead, he focuses on a slightly different argument: that contrary to conventional wisdom, consuming more carbs during exercise does not make you faster. In short, he argues that the only benefit of ingesting carbohydrates during exercise is that it keeps your blood sugar high enough to fuel your brain, which would otherwise make you feel groggy. tired That would explain why many studies have found performance benefits from sports drinks, even though Podlogar and others have found that very high carb doses don’t actually deplete internal carb stores. . To maintain blood sugar, Figures of Noakewill only need 20 grams of carbohydrate per hour, regardless of whether you usually eat a low-fat or high-fat diet.

So should we push our carb intake up to 120 and beyond, or dial it back to 20? The honest answer, at this point, is that both ideas are speculative. The world of elite endurance sport is voting with its feet (or, perhaps, with its gut) in favor of carb-mania. My guess is that they are right, assuming your main interest is winning races in Olympic sports. But we must remember that no one has proven that 120 grams per hour makes you faster than 90, and even the case for 90 over 60 is not watertight. The only way to resolve the argument is through more data from well-designed experiments or temporarily, like Mathieu van der Poel, through winning races.


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