Nick Norwitz examines whether athletes need carbs using data from the FASTER trial comparing low-carb and high-carb elite runners. The low-carb group burned 2.3 times more fat per minute and maintained muscle glycogen without eating carbs, suggesting keto-adapted athletes can perform without carbohydrate loading.
Do athletes need carbs? This is a question that comes up again and again, so I thought I'd take a whack at addressing it, but in kind of a fun, cheeky style. So I'm going to talk about some data, but you can already see this is a split-screen video, and throughout the entire video, the one side of the screen, I'm going to be doing a straight set of push-ups, at least 100 push-ups with a little bit of extra spicy sauce at the end. But what I really want to talk about in this video is data from the FASTER trial. This stands for Fat Adapted Substrate Use in trained elite runners. This was a study comparing 10 high-carb versus 10 low-carb elite runners, looking at the, uh, difference in ability to burn fat and also glycogen stores. So we're going to go over those two pieces of data, but first let's characterize the groups. The low-carb athletes were eating about 10% of their energy from carbohydrates, about 80 grams per day, versus the high-carb athletes were eating 684 grams per day of carbs. And the low-carb athletes, importantly, had been low-carb for at least 6 months, although the average was closer to 20 months. So these were athletes that had been low-carb, keto-adapted, or keto-adapting for a long period of time. Now, the first question: was there differences in the athlete's ability to burn fat between groups? Absolutely, a resounding yes. The low-carb athletes had a 2.3-fold higher level of maximal fat oxidation, maximal fat burning. So it was 1.54 grams per minute fat burning in the low-carb athletes versus 0.67 in the higher-carb athletes. And to wrap some context around that, that means from fat alone, the low-carb athletes could burn about 830 calories per hour from fat alone, which is really astonishing. And prior work had suggested that could only burn I don't know, 1 gram per minute of fat. This was showing the average was more than 50% higher than that, probably because these athletes were so long keto-adapted. It takes time for the metabolic machinery to change in our bodies. So that was one difference between the groups, that the low-carb athletes could burn a tremendous amount of energy in fat. And this adaptation probably took a really long time. Again, average time low-carb was about 20 months. Now, the other question, muscle glycogen, because you do want glycogen in your muscles, especially to support highly glycolytic activity, things like sprints, so that the carbs can go through glycolysis and generate maybe not efficient, but fast energy. So, one might think, "Oh, the low-carb athletes not eating carbs are gonna have lower muscle glycogen." Incorrect. What they found in the study is the low-carb athletes had the same baseline muscle glycogen, the same glycogen in their muscles after a 3-hour treadmill test, and the same muscle glycogen even 2 hours post-recovery. And this despite ingesting far, far fewer— over tenfold fewer carbs in the post-exercise period. And this kind of makes sense, right? Because over time, the body's going to adapt to use carbs more efficiently, and burning fat is going to be carb sparing. But a question arises then: well, where does carb replenishment come from? The body does this cool thing called gluconeogenesis. Maybe you've heard of it, but it can turn other things into carbs. Like, uh, glycerol. So glycerol is the backbone of stored fat. So if you're increasing your fat oxidation, your fat burning, you're liberating the free fatty acids, those are going into beta oxidation generating fuel, and the glycerol can be burned for fuel as well, or turned into carbohydrates via gluconeogenesis. Glycerol goes up more if you're keto-adapted, and that can then be used to replenish carbs in the postprandial period, so you can store those carbs and use them, have them, for highly glycolytic activity. So overall, what they found in this study was that the keto-adapted athletes did not have impaired performance by any means. They had a massive upregulation in their ability to burn fat as fuel, and they didn't have decreases in muscle glycogen. Now, I would say in certain circumstances, dietary carbs can definitely benefit athletes, but it's potentially a trade-off in any individual. So for me, for example, maybe I take a little bit of a hit by being chronically keto in terms of my athletic performance, but it's worth it for me because now I don't have, you know, flaring IBD. So you have to take things, of course, in context, but I wanted to address this question. I hope you found this video kind of fun and different.
Nick Norwitz, what he accomplished is the most amazing thing I've seen in my 11 years of teaching in PE. I've conducted the fitness test all 11 years, every year for numerous kids, you know, 100 to 200 kids a year. I've seen some super athletic kids, some kids that actually wanted to achieve just an A standard in push-ups that would train outside of school. And initially when Nick asked me what the record was, it was 72. That's what I was thinking he was shooting to break, you know, that he'd be pushing himself to reach that 72 mark. And 72 came, 100 came, 150 came, 200 came, and finally Even up to 239th push-up where he fell on the 240th, he wasn't shaking, wasn't convulsing with his body. He was just so strong. It is just unbelievable to me how he physically can do this. I've just never seen anything like this. Just unbelievable. I mean, so unbelievable that people think it's a joke. And it's no joke, and the kid is unbelievably strong.
It was very helpful with my— all my peers were cheering me on. On after I got to 70, which I knew I could do because I'd done, um, much more before, and really taking each one in stride and just like I did 100, I'm like, alright, I'm just gonna go to like 110, just do a couple more, and then I just kept going with that until I couldn't do anymore. As for mental preparation before, um, there wasn't too much pressure just because it was a school, a school whole thing, but you just gotta face it and that was the hardest part. The beginning is the hardest. Once you're in, you can just tell yourself to keep going, and the best part was definitely afterwards, or the last few, when even though you know you're like in a lot of pain and you know you're gonna drop soon, that you've done a certain amount and you can be proud of that.
