Everyone eats. Not everyone fuels.

One of the challenges with nutrition is that it feels familiar. Everyone eats, everyone has preferences, and most people have at least some sense of what works for them. That familiarity makes it easy to assume we’ve got it figured out, even when something isn’t quite clicking in training.

In this conversation, Stevie Lyn Smith brings a different lens to it. As a registered dietitian and endurance athlete, she isn’t focused on perfect plans or rigid rules. What stands out is how often she sees runners doing a lot of things right, but missing something foundational.

Not training. Fueling.

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When runners struggle with energy, performance, or recovery, the first instinct is usually to adjust the training plan. More structure, more intensity, maybe more volume.

What rarely gets questioned is whether the body has enough support to handle that work.

Stevie talks about how often athletes come to her thinking they need something advanced, when the reality is much simpler. Their daily carbohydrate intake is far below what their training actually demands. Not slightly off, but meaningfully low over the course of a week.

That kind of gap doesn’t always show up immediately. It builds slowly, in the form of fatigue that lingers, workouts that feel harder than expected, or long runs that take more out of you than they should.

There’s a tendency to treat fueling as something that matters only on race day or during long runs. The rest of the week becomes an afterthought, especially for runners balancing work, family, and everything else.

Stevie pushes back on that idea.

Fueling during training isn’t just about getting through a workout. It’s part of how the body adapts to the work you’re doing. When carbohydrates are available during runs, the body can rely less on its stored energy and recover more effectively afterward. Over time, that consistency adds up.

This is especially important for runners who don’t have the luxury of extended recovery time. If you finish a run and immediately move into the rest of your day, whether that’s meetings, childcare, or both, the way you fuel can shape how you feel for hours afterward.

As training volume increases, the margin for error gets smaller.

Runners preparing for marathons or ultras often focus on the logistics of race day fueling, how many gels to carry, how often to eat, what sits well. Those details matter, but they are only part of the picture.

The broader challenge is meeting the total energy demands of the week. Long runs, back-to-back workouts, and higher mileage all increase the need for carbohydrates, fluids, and overall intake. When that demand isn’t met, the body compensates in ways that aren’t always obvious at first.

Stevie emphasizes that fueling should feel repeatable. It should be something you can practice, adjust, and actually execute, not just something that looks good on paper.

Protein is having a moment, and for good reason. It plays a role in recovery, muscle repair, and overall health. But in endurance training, it often gets more attention than it needs at the expense of carbohydrates.

Stevie keeps it grounded. There is a range that works for most runners, and it doesn’t require extremes. The bigger issue she sees is not a lack of protein, but an imbalance. When protein intake climbs while carbohydrate intake stays low, performance tends to suffer.

In longer races, protein can become part of the strategy, especially over several hours. Small amounts can help with satiety and reduce muscle breakdown, but it works best when it complements a consistent carbohydrate intake.

Hydration advice tends to get simplified into rules that don’t apply to everyone. Drink this much, take this amount of sodium, follow a set formula.

Stevie approaches it differently.

Sweat rate and sodium loss vary widely from person to person. Some runners lose a lot of fluid with relatively low sodium, while others lose less fluid but a higher concentration of sodium. The only way to understand what works is to pay attention to how you feel during and after runs, and to adjust based on that feedback.

More isn’t always better. Too much sodium can create its own issues, just like too little. The goal is to find a balance that supports performance and keeps things feeling steady.

Nutrition advice is everywhere, and not all of it is useful.

Stevie points out how easy it is to get pulled toward messaging that feels urgent or convincing, especially when it plays on fear or promises a quick fix. The more extreme the claim, the more important it is to step back and look at what’s actually being said.

What she comes back to is consistency and practicality. The best approach is usually the one you can maintain, the one that fits your life, and the one that supports your training without adding unnecessary complexity.

Most runners are willing to put in the work. They show up, follow their plans, and push through tough days.

What this conversation highlights is that effort alone isn’t the whole equation.

Fueling shapes how that effort is absorbed, how the body adapts, and how sustainable the process feels over time. It doesn’t have to be complicated, but it does need attention.

For a lot of runners, making progress isn’t about finding something new. It’s about supporting what they’re already doing in a way that actually allows it to work.

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Jon is a runner, cyclist, and podcast host from Boston, MA, who now lives in Boulder, CO. For The Long Run is aimed at exploring the why behind what keeps runners running long, strong, and motivated.

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