Should Athletes Eat Go Low Carb?

Hey athletes! It's team dietitian Erika! As your friendly RD, I’m here to bring some balance to the conversation about fueling for your activities stemming from this study. There's a lot of buzz around carbs (CHO) and their role in keeping you fueled during exercise, and I want to lay out a well-rounded perspective that considers all angles.

Now, let's acknowledge that the science is vast, and sometimes we see bits of research being highlighted to support specific trends, like low-carb diets. It's essential to remember that some recent findings might seem to favor lower-carb approaches, but we must consider potential biases, especially when there's an involved interest, like in the case of this study, with ketone companies (the authors present conflicts of interest).

Despite these discussions, decades of research along with extensive clinical experience consistently show us that carbs are vital for sustaining energy, particularly during prolonged or intense exercise. Carbohydrates traditionally serve as a reliable fuel, quickly accessible to your muscles and brain, helping keep your performance sharp and focused, and preventing that dreaded exercise-induced hypoglycemia (EIH, aka, bonking).

While some newer studies suggest that consuming smaller carbohydrate amounts might support endurance activities, for most of you, ensuring your carb intake is adequate is crucial. Here's why: Adequate carbohydrates help maintain muscle glycogen stores, providing that burst of energy when you need it most. Without enough carbs, you risk running out of steam too soon.

Finding the right balance is key. 

Let’s break it down further:

This review presents an interesting hypothesis, but it's important to recognize what it is: a selective interpretation of existing research that supports a pre-determined conclusion about low-carb approaches. When authors have conflicts of interest with ketone supplement companies and a history of promoting low-carb approaches, we need to read their conclusions with healthy skepticism. As far as types of studies go in the research world, this type of study is relatively weak in terms of strength of evidence, and does not include original new research.

What They're Downplaying or Ignoring:

While exercise-induced hypoglycemia (EIH) certainly matters, this review glosses over decades of robust research showing:

  • Performance benefits of adequate carb intake across various sports and intensities that can't be explained by blood sugar alone

  • The dose-dependent relationship between carb intake and performance in countless studies, especially at higher intensities and in events under 2-3 hours

  • Glycogen's role in power output, repeated high-intensity efforts, and sprint performance, which is where many recreational athletes actually compete

  • Real-world evidence from elite athletes who consistently perform better with higher carb availability

  • The metabolic cost and adaptation period of low-carb approaches that may not suit recreational athletes with limited training time

  • The fact that low carbohydrate availability can contribute to low energy availability (LEA) symptoms and also impacts ferritin status and iron absorption along with many other micronutrients

  • The negative impact low carb diets can have on gut health

Your Experience Matters:

The claim that "15-30g/hour works just as well as 90-120g/hour" contradicts what we're seeing with athletes, and for good reason. That recommendation might work for ultra-endurance efforts at lower intensities when combined with other fuel sources, but it's woefully inadequate for:

  • Athletes doing tempo runs, tough race-pace efforts, or interval training

  • Team sport athletes with repeated high-intensity bursts

  • Cyclists or runners racing at higher intensities

  • Anyone trying to maintain power output, not just "finish"

The Real Nuance:

What this review gets right: Blood sugar stability matters, especially in ultra-endurance events, and individual variation exists in carb needs.

What it misses: Adequate carbohydrate intake supports performance through multiple mechanisms, not just preventing hypoglycemia. Muscle glycogen availability affects:

  • Your ability to sustain higher intensities

  • Power output during critical moments

  • Recovery between training sessions

  • Immune function during heavy training blocks

  • Central nervous system function

Our Message to Athletes

This research offers one perspective, but it's not the full picture. What I see consistently in practice is that recreational athletes who fuel adequately with carbs tailored to their training intensity, duration, and goals perform better, recover faster, and feel stronger. While some outlier ultra-endurance athletes thrive on lower-carb approaches, that doesn't mean it's optimal for your Saturday morning half-marathon or century ride.

Let's focus on what works for YOUR body, YOUR sport, and YOUR performance goals, not on a one-size-fits-all approach that cherry-picks research to support a particular dietary philosophy. If 15g of carb per hour yielded the best performance outcomes for most athletes, Holley and I wouldn't constantly be seeing athletes struggling to meet their health and performance goals in practice taking in this much. Most of our clients are fueling below 60g carb/hour before they start working with us & are running into trouble- oftentimes fueling properly (which may include fueling MORE) is the best strategy.

So, if you need an energy boost for your next event or want to refine your everyday nutrition strategy, let’s chat! We’re here to customize a fueling plan that's perfect for you, so you can stay energized and reach those fitness goals while feeling your best. Together, we'll craft a strategy based on the comprehensive evidence and practical insights suited for your athletic journey.

Holley Samuel