The History of Fueling Endurance Performance

January 11, 2023

The landscape of endurance sport fueling began with carbs, and is ending with carbs, and in this area in particular, the research has lagged the practice of athletes perhaps more prominently than any other area.

Much before 1985 or so, and you pretty much just had Gatorade at the helm of sport nutrition science and every football and basketball player in the country just knew that if they downed the stuff like it was going out of style, they were going to feel better than if they drank water alone, or nothing at all.

Gatorade Original was the antidote to the wild west of the “water makes you weak” era. The athletes knew it. The researchers knew it, and it was time for the researchers to figure out why. In 1990, it was 30-60 grams of carbohydrate per hour. That’s all that was recommended for fuel intake during endurance training and racing. The carbohydrate supplement industry was beginning to blossom. Options were appearing left and right.

After 1990, folks would still debate for years whether galactose or glucose was the best option for sugar consumption. It seemed intuitive that galactose, being slower to absorb, would steady out the blood sugar and prevent crashes, but glucose could rescue from sugar crashes and absorb faster, maybe easier on the gut, too.

If you don’t know where the galactose vs. glucose debate ended, there’s a reason why galactose isn’t in any of your favorite products. Slow carbs limit max uptake rates.

Uptake here means how much your gut can absorb into your bloodstream. Intake on the other hand means how much you consume. Galactose limits uptake rate, so it’s better to intake more glucose, instead. Consume too much galactose and you’ll have gut issues.

On the opposite side of the 30-60 grams of carbs coin, back in “the day” there were rumors of superhuman pros who’d managed 600 Calories in an hour, or about 150 grams of carbs per hour, so surely the oft-cited “optimal” 30-60 grams hourly carb intake rate wasn’t the maximum humans could do. Surely there was a gray area above that. Nobody knew how much. Nobody knew how to reliably use this gray area without ending up in the portaloo.

To confuse things further, between 1990 and 2010, and even still today, you’ll find calories per hour numbers thrown around as if those are good and useful recommendations. They’re not, in case you’re wondering. If you’re not sure why I make such a bold claim here, check out my previous article for a very fun analogy. You can get disastrous GI effects from 300kcal of mixed protein, fat, and carbs, in the wrong composition, but have no GI issues whatsoever using other compositions of primarily carbohydrate. 200 Calories, 300 Calories, maybe 350 or 400 Calories, and on and on the overly vague recommendations from coaches and nutritionists poured in.

By 2011, 90 grams of carbs per hour during long activities was the new hotness (roughly 360 Calories per hour). Or so the journals said.

Was it really? No, but that’s what they said. Why? Who knows. But anyone who knew anything about endurance sport fueling through the two-thousand teen years was starting to have their interest piqued by this new 90 grams of carbs per hour intake rate. “Multiple transportable” was becoming household terminology. Or maybe that’s new for you. It just means glucose + fructose. Regarding why the 90 stuck so hard…It was certainly coincidental with some pretty infographics and charts that came out in conjunction with a big marketing push from a company whose name rhymes with haterade. I’ll leave that there.

Okay, one more morsel. They weren’t the only ones. Don’t be too hard on them. Pepsi’s Gatorade, and Nestle’s PowerBar endurance mixes stuck to these 60 & 90 numbers for a long time. Okay, actually, they still do.

In reality, research had established by 2010 that there was strong evidence that>100g per hour might be useful, and was definitely tolerable for some folks, and it wasn’t just the elites. Of course, I didn’t hear about that in my undergrad or masters programs, at the time. And neither did you, unless you were in the bleeding edge internet forum threads discussing this kind of thing.

I heard something like “up to 60 grams of carbs for activities up to 2.5 hours and that for 3 hours and longer, up to 90 grams of carbs per hour might be useful.”

At the time, I couldn’t have cared less. The longest run my legs had ever carried me through, in 2010, was a stress-fracture inducing 10 miles. I was a decathlete. I looked more like a hammer thrower. My idea of endurance was a 4:57 1500m at the end of 2 days of competition. And it hurt. Accordingly, I didn’t even think to check what the scientific literature actually said about 3-hour races. It was irrelevant to me. My future wife was still competing alongside me in the 100m hurdles and heptathlon. We looked at the cross country team in awe. So I swallowed my textbook’s dogma of 60-90 grams of carbs per hour, and chased it with a swig of Gatorade.

A position stand is an article written by many leading experts to summarize best practices in a certain domain. I read many of these in my academic years. Mild sarcasm ahead. You’ve been warned. Surely, the position stands that said 90 grams of carbs per hour was the upper-end recommendation couldn’t have been so misinformed and so cautious as to have underreported the optimal intake. Surely they could not have ignored the ability for many athletes to safely consume more, especially when it could be beneficial for so many people, including complete novices. Surely, if folks were taking in more than 100 grams of carbs per hour, they were the elites, superhuman in their energy burn, and in their iron guts. It couldn’t possibly include regular folks. Right? Turns out, those position stands did flatly ignore big important findings, and only now in the last 2 years have studies started to point towards higher fuel intake rates for us mortals. Why that happened is open for interpretation.

Thankfully, we’re past that era. The era was defined by two major camps. The “high-carb” folks touted the benefits of a high carb diet, and 90 grams of carbs per hour for endurance sports. The other camp was the low-carb high-fat group. Sometimes called keto. Sometimes fat adaptation. I’m happy to report that it’s not just the “carbs vs. no carbs” camps anymore, and it’s well-established that carbs in excess of 100 grams per hour are tolerated during training and racing. These carb amounts are well-tolerated by regular folks and elites alike. It just has to be implemented sensibly and sometimes with a little individualization.

When activities are>4 hours long as they usually are if your sport is 70.3, 140.6, or grinding through midwest gravel, high carb fueling absolutely is performance enhancing. It’s not just “60 to 90 grams of carbs” anymore. That’s so 2000’s of you. But I certainly don’t blame you. It goes much higher. And easy sessions can sometimes be much lower. It depends. More on that in upcoming articles in this series.

The field of academics, myself included, has done a remarkably poor job of spreading good and useful information, simply because it’s complex to optimize and individualize. It takes nuance and some experience. There are lots of very experienced athletes (and you may be one) who has very intuitively figured this out on your own. Everything has been painted with a broad brush. We have the technology, and the research, and the brainpower to get much more specific with our recommendations but it’s just hard to convey those specifics to all people, all at once, with out having some of the people be very poorly served by the recommendations. Hence, we keep painting with a broad and generic brush.

Regarding the upper limit, it took a unique set of circumstances for me to realize just how preposterous the 90 gram upper limit was. That’s a story for another time. It involves a gorilla on a bike. Sometimes well-documented anecdotes are just the right antidote to dogma in the scientific literature.

It might be a few years until a really solid review paper or position stand comes out and says “>100 grams of carbs per hour can be performance enhancing,” but it’s coming. Mark my words.