Running Nutrition Questions Answered: Carbs, Ferritin, Burnout, and Your First Marathon

Episode: S6E30 | Stevie Lyn Smith, MS, RDN, CSSD, CDN (with co-host Coach Amanda Katz) | Aired September 24, 2026 | 1:04:00

Podcast Hosts: Nick Klastava & Amanda Katz

Author: Nick Klastava

Listen: Spotify | Apple Podcasts | YouTube

You sent in your running nutrition questions, and I knew exactly who to call. For our first old-fashioned listener Q&A episode, Coach Amanda and I brought back fan favorite and certified friend of the pod Stevie Lyn Smith, MS, RDN, CSSD, CDN. Stevie is a board-certified sports dietitian with more than 14 years as a dietitian, almost a decade working with endurance athletes, and ten full Ironman-distance triathlons on her own resume. Seven questions came in and we took apart every single one: how many carbs to take on a long run, how to juggle fast 5Ks with long distance and heavy lifting, how to keep from burning out, how to get your brain to believe what your legs already know, how to run a first marathon without meeting the wall at mile 20, why runners need more ferritin than everyone else, and whether it's smart to cut weight before a marathon. Spoiler on that last one: no. Here's everything we covered, plus the parts I wish every runner heard before their next training block.

Key Takeaways

• For runs and races over 90 minutes, Stevie recommends 60 to 90 grams of carbohydrate per hour. Your number is the one you can tolerate and execute on race day.

• Your long run starts with the carbs you eat the day before and ends with the recovery meal after.

• Your gut is trainable. Start practicing race-day fueling months out, not during taper.

• You can love 5Ks, marathons, and heavy lifting. Just don't make all three the priority in the same season.

• Most burnout is self-inflicted through race stacking, and underfueling makes the mental side worse. Your brain needs about 120 grams of carbohydrate per day just to function.

• Resiliency data points, real moments where you did something hard, shut down self-doubt faster than a borrowed mantra.

• For a first marathon, practice race breakfast, do a one-day carb load before three long runs, and make "finish strong and learn" a real goal.

• Ferritin is one marker, not your whole iron status. And don't chase weight loss during a marathon training cycle.

Running Nutrition Questions Start With Long Run Carbs

Question one set the tone: "I have a half marathon in December, but I'm still struggling with how many carbs to take on my long run." Stevie did what every good sports dietitian does and answered with more questions. How many carbs before? How many during? What's the actual struggle? Then she gave us the number.

For anything over 90 minutes, training or racing, Stevie wants runners in the range of 60 to 90 grams of carbohydrate per hour. Some sports dietitians say you don't need 60 grams until the two-hour mark, and there's flexibility there, but her preference is to start fueling in that range once you cross 90 minutes.

Here's the nuance that matters. Stevie sees two failure modes all the time. The first is the runner who does the bare minimum. The second is the runner who decides 90 grams per hour is the only acceptable answer because more is more, and then can't pull it off on race day. If 90 grams wrecks your stomach, it isn't your number. Your number is the one you've practiced, tolerated without GI drama, and can repeat when the gun goes off.

She also had zero patience for the "I have nowhere to put my gels" excuse. Running shorts and vests have more pockets than ever. For context, most gels land around 20 to 30 grams of carbohydrate each, so 60 grams an hour usually means two to three gels, and 90 grams means mixing in chews or a carb drink mix.

Fuel Before, Recover After, and Train Your Gut Early

I took the question as mid-run fueling too, but as a coach I want to zoom out for a second. Long runs don't exist in a vacuum. I encourage my athletes to carb load the day before a long run, and sometimes two days before if the run is long enough. And the run isn't over when you stop your watch. The run is over once you start your recovery, and your recovery is whatever you put in your body afterward.

The pre-run carbs directly support the run. The recovery meal indirectly supports it, because you recover faster and show up to the next session in a better place. Stevie backed this up: carbs after long efforts give you the energy to actually live your life instead of crashing into a two-hour nap after every weekend long run.

Amanda added the part this runner needs most. A December half means a ton of runway (pun unintended, she swears). Don't experiment with gels for the first time in late November, when Thanksgiving stress is high and you're in taper. Your gut can be trained just like the rest of your body. Start now, on every long run, at the paces you'll actually race.

How to Prioritize Fast 5Ks, Long Distance, and Heavy Lifting

Question two came from someone who loves everything: "I love racing fast 5Ks, but I also love long distance. How do I prioritize training? I also like to lift heavy." Amanda took this one first, and her answer came down to one word. Seasons.

You have an entire year (heck, an entire life) to do all of these things. What you don't want is fast 5K training, 16-mile weekend long runs, and heavy lifting four to five times a week crammed into the same block. Maybe January through March or April is your fast and short season, with two to three quality sessions a week. You can still lift, but heavy is relative, and if the speed work leaves you cooked, scale the lifting back. That's fine.

Then maybe there's a season where lifting is the priority. You're running three days a week, mostly easy, basically in a base-building phase for general fitness. The goal of that season is progressive overload in the weight room, and the speed work and the distance can wait. Then maybe you decide you want a fall half or marathon, and you start that build in May or June. Amanda's point was that trying to do all of it at once isn't just a physical problem. It's a fast track to mental burnout too.

Stevie loved the seasons idea too. When you finish a marathon block and need a break, you don't feel lost. You recover, step into a strength-focused season with a new goal, and carry that strength into your next marathon cycle.

Your Training Week Doesn't Have to Be Seven Days

As someone who ran in college, my entire life was built around seasons: cross country, indoor, outdoor. So Amanda's answer hit home. A lot of runners are stuck in one template: speed workout during the week, long run on the weekend. That's not the only way a week can look.

In a 5K block, you might do three quality sessions a week. That sounds intimidating until you realize they're shorter sessions, and the long run is shorter too (sometimes run the day after a workout just to fit it in). In the off-season, while you're base building, lift heavy. Then take that strength into an endurance block with one workout a week and a long run with some work in it.

You also don't have to live on a seven-day calendar. Some older athletes train on a 14-day week and only do a long run every other weekend to stay healthier. There's some research suggesting experienced runners don't need a long run every single weekend because of the fatigue that stacks up (marathoners probably still do). Some runners use 10-day blocks. It feels weird to end your week on a Wednesday, but it builds real recovery into the cycle.

How to Keep From Burning Out

Question three was simple: "How do you keep from burning out?" Stevie teed this one up perfectly without even knowing it was coming. I took it first, because this one is personal. I'm on my third act of running. I burned out in high school and college, came back, and burned out again (the pandemic didn't help). I took eight years off, came back, and got faster at 38 than I was at 20. So I say this with a lot of lived experience: we all go through it.

First things first, it's okay to take a break. It's okay to say "I don't want to run this week" or this month, and do something else. Your fitness can come back. I promise. It is far better to make that choice on purpose than to keep dragging yourself out the door because you're afraid of losing fitness and missing your goals. All that does is kick the can down the road until your body or your brain shuts the whole thing down for you, and then you're missing way more time.

Second, switch it up. Maybe you're burning out because you run a marathon every single block. Marathons are one of the biggest mental drains in this sport: a lot of fatigue and a lot of 4 a.m. summer alarms. If my long run is eight or ten miles, I can sleep until 9 a.m. and still go suffer. Change your races. Train without a goal for a while.

At the end of the day, this is our hobby. We don't have to hold ourselves to anyone's standards. We're free to do what we want.

We Do It to Ourselves: Race Stacking and Lottery FOMO

Amanda took this question and absolutely ran with it. She pointed back to our episode with Coach Corky on back-to-back marathons as a great listen, even for non-marathoners, because it's really about how you build out your year. Then she introduced us to her personal condition: JOMO, the joy of missing out.

Her point was that we create most of our own burnout. It's the pressure to run the same spring race every year because you always have. It's entering twelve fall marathon lotteries and somehow getting into Chicago and New York in the same season, then deciding you'll "party pace" one of them (her hot take: there's no party pace in a marathon, because your body doesn't know that setting). Then it's the United NYC Half, the Brooklyn Half, a charity bib, and roughly two hours off before summer training starts. Stevie and I were laughing because we hear some version of this every year. Where's the lie?

Amanda also explained why coaches aren't getting replaced by AI anytime soon. An athlete in peak marathon training has a wedding, a bachelorette, and a sudden urge to see Utah the weekend of their 20-miler. Coaches pivot the plan, move a day, or add a deload week. Those are the small fixes. The big one is planning your seasons before the lottery emails arrive.

The Running Nutrition Questions Hiding Inside Burnout

Stevie co-signed all of it and then added the piece most people miss. She's been there herself: seasons with two full Ironmans, five or six weddings, a full-time job, and a part-time job. Burnout, check. That's part of why she values a coach who can see a bad idea coming before you can and say "let's hold the phone."

Then she brought it back to fueling. All those life events are load. When you're traveling, at a bachelorette until 2 a.m., or a bridesmaid who needs to be full glam by 7 a.m. and supposedly has no time to eat, the underfueling adds up fast if that's a regular theme in your life. That doesn't mean you can't do the races and the fun things. It means eating enough to support not just your training but your whole life has to be part of the plan.

Here's the nerdy fact that stuck with me. Your brain runs on glucose, and Stevie noted that you need a minimum of about 120 grams of carbohydrate per day just for basic brain function. That's before a single mile. When you don't eat enough, it can amplify anxiety, flat mood, and depressed mood. So when someone tells Stevie they feel burned out, one of the first running nutrition questions she asks is whether underfueling is part of what's driving it. Sometimes the fix for "I hate running right now" starts at the kitchen table.

How to Help Your Brain Catch Up to Your Running

Question four: "How can I help my brain catch up to the running?" In other words, my fitness is improving but I don't believe in my abilities yet. I jumped on this one because belief is one of the most important things in athletics, and nobody talks about it enough.

People try to replace belief with hard work. Some can, until they can't. Your absolute peak is going to come from trusting all the work you've done, and the perfect training block doesn't exist. In marathon training, you're never going to run 26.2 miles at marathon pace before race day. If you did, you just ran your race. At some point, you have to believe you can do the thing you trained for.

So how do you build that? I use something I call resiliency data points. Mantras are somewhat effective, but they're words someone else said. Deep down, your body hears them and goes "cool, that guy said a thing, I still don't believe I can do this." Resiliency data points are moments from your own life where you did something you didn't think you could do. Say you ran a 20-miler and were still on marathon pace at mile 17. At mile 17 of the race, you can look at yourself and say: here's evidence, I've already done this, why can't I do it today?

The goal is to quiet that doubt fast. Let it sit for two miles and you've suffered for two miles. Ruminate on a bad run for two days and it shows up in your Wednesday workout, and suddenly you're spiraling about the whole block. Everyone has resiliency data points. You've conquered everything that's come your way so far to get here. Use it.

Amanda said she had no notes and tried to drop her mic. Then she had notes. What if you need to believe in yourself but genuinely don't have the evidence yet? Then the question becomes: what would I need in order to believe I can do this? Maybe you need a run coach to program real speed work and marathon tempo runs. Maybe you need a sports dietitian because you keep bonking in races. Figure out what's actually stopping you.

Stevie's go-to line in rough patches is "you've done more with less." Race day is when you're rested, tapered, and carb loaded. If you nailed your training while life was messy, race day is the fun part. For first-timers, she likes to chunk the distance down. How many 5Ks have you run? How many 10Ks in training? Break the race into smaller, more digestible pieces. (Dietitian pun fully intended.)

How to Run Your First Marathon Without Hitting the Wall

Question five came from a first-time marathoner running Philly this November. They're at about 42 miles per week, running five days a week, peaking at 50. Their longest run is 20 miles. Their A goal is under 4:15, but they think sub-4 might be possible. Their long runs are at about 9:30 pace, and they can't break 1:50 in the half without really pushing. The question: how do you push without ruining your first race?

Stevie went first, and fun fact, she's running Philly too. Her checklist starts with race morning. Practice your pre-race breakfast and its timing before a couple of your long runs. Philly isn't a logistical nightmare like New York, so you don't need to recreate a 5 a.m. bus-to-Staten-Island morning, but you do need that breakfast on lock.

Next, practice your carb load. For newer athletes, Stevie likes to see a one-day carb load done before three long runs during the build. More experienced athletes can do it more often if they want. She thinks of it as an insurance policy for restocking glycogen during peak weeks, because it's easy to fall short without meaning to. And write it down. Write down the foods, how close you got to your carb load target, and how you felt. What works for Stevie is different from what works for Amanda or me. Stevie ran her first marathon in 2009 and her own carb load has evolved a lot since. When race week comes, you want a list, not a scramble.

Finally, practice in-run fueling on every long run, plus your midweek medium-long runs and tempo efforts at marathon pace. Fueling at a relaxed long run pace and fueling at goal pace are two different skills.

Make Finishing Strong a Real Goal, Not a Consolation Prize

My perspective here has only gotten stronger the longer I coach. The marathon is a big jump from the half. More likely than not, your first one won't be your fastest. What I don't want is an athlete who puts so much pressure on a time goal that they miss it and never want to run another marathon.

Amanda doesn't set time goals for athletes tackling any distance for the first time, especially the marathon. The process ends up more joyful without that extra burden. She also pointed out that Philly is not a fast and flat course. Maybe it becomes the marathon you return to and chase a time with real data behind you. Or as I put it, Philly's a little hilly.

Why Runners Need Higher Ferritin Than Non-Runners

Question six: "Why is it important for runners to have higher ferritin levels than non-runners?" This one landed perfectly, because the new ferritin guidelines were all over everyone's feeds the week we recorded. Runners love to talk about their ferritin. Stevie started with the basics.

Iron is an essential mineral found in your red blood cells. It plays a critical role in transporting oxygen to your working muscles, and it's also involved in energy production, immune function, and cognition. Ferritin is a protein that stores iron, which is why it's used as a marker of iron storage. Stevie's dream is for all of her athletes, female athletes in particular, to have a baseline ferritin level on file (along with a DEXA scan, but that's another episode).

Now, the guidelines. The American Society of Hematology (ASH) published its first clinical practice guideline on diagnosing iron deficiency in September 2026, and it raised the ferritin cutoffs. For most adults, including menstruating individuals, the diagnostic threshold is now 30 ng/mL or below, with higher cutoffs for higher-risk groups. Stevie made an important distinction: these are diagnostic thresholds, not optimal ferritin targets for athletes. The big win is that a runner with a ferritin of 15 is much less likely to be told they're fine.

So why are runners at higher risk? Stevie's list: high training loads that drive inflammation (and the hepcidin response that limits iron absorption), low energy availability, low carbohydrate intake, GI issues, menstrual losses, and foot-strike hemolysis, which she considers the least important of the group.

Ferritin Is Not Your Whole Iron Picture

Here's where Stevie says a lot of runners lose the plot. Ferritin matters, and you should keep tabs on it, especially with a history of iron deficiency or if you feel terrible in training. But ferritin alone doesn't tell the whole story. She wants to see the full iron panel, including transferrin saturation, serum iron, and total iron-binding capacity (TIBC), plus a complete blood count (CBC).

Why? Inflammation. Stevie explained that inflammation can falsely elevate ferritin by something like 30 to 90 percent. (The new ASH guideline also calls for adding transferrin saturation in people with inflammation for this exact reason.) So a "fine" number can hide a problem, and a low number still needs context. If your ferritin is 20, sure, you probably won't feel great. But why is it 20? Low carbohydrate availability? Low energy availability? Both? A training load that's not leaving room for recovery? Something along the iron transport chain, like another micronutrient?

I've heard way too many stories of runners talking their way into an iron infusion based on a single ferritin number. That's dangerous. Stevie shared that one client felt worse after her infusion (she went into overload) than she did when her ferritin was 2. More is not automatically better. Talk to your providers and test the full picture.

Amanda's summary: test, don't guess. And unfollow the influencers cherry-picking bloodwork advice. That's why sports dietitians exist. For the full deep dive, listen to our ferritin, iron, and anemia episode with Callie Roseland.

Can You Safely Cut Weight Before a Marathon?

The final question: "Can I safely cut pre-marathon for performance?" Stevie opened with "can we safely cut a pizza? A bagel? Yes." Then she got serious.

If you're in the off-season and body composition changes are appropriate, carefully calculated weight loss can be on the table. But if you're three to four months out and in a marathon training cycle, her answer is no. The priority during a training cycle is eating to support your training, your adaptations, and your overall health. Living in a deficit while training hard is not fueling for health and performance. Stevie approaches weight loss goals very delicately and only works on them with athletes one on one, in a very small caloric deficit, with health as the first priority.

Amanda agreed completely. Marathon training is not the time for weight loss goals. And cutting right before training isn't a loophole. It just means you're putting your body in a deficit right before you ask it for so much. As a personal trainer who works with runners on body recomposition, she looks at it through the same lens as the rest of this episode: seasons. The season right before marathon training is when your mileage should be climbing so your body is ready for multiple days and hours of running each week, plus strength training, plus just living your life.

Her final answer: everything Stevie said, and a bag of potato chips.

What All These Running Nutrition Questions Have in Common

Seven questions, and almost every answer came back to two ideas: fuel like you mean it, and build your year in seasons. Most running nutrition questions have simpler answers than the internet makes them seem. The hard part is doing the boring stuff consistently.

Got more? Send them to hello@runningexplained.com. We loved this format, and another Q&A episode is coming.

Guest Bio

Stevie Lyn Smith, MS, RDN, CSSD, CDN, is a registered dietitian and board-certified specialist in sports dietetics with more than 14 years of experience as a dietitian and almost a decade working with endurance athletes, including runners, triathletes, cyclists, and swimmers. She founded Stevie Lyn Nutrition, a virtual sports nutrition private practice, hosts the Real Fuel with SLS podcast, and co-authored Power Up: A Young Woman's Guide to Winning with Sports Nutrition with Molly Hurford. An endurance athlete herself, she has completed ten full Ironman-distance triathlons and ran her first marathon in 2009. She's also a dog mom of two. Find her on Instagram at @stevielynlyn or at stevielynrd.com.

Frequently Asked Questions

How many carbs should I take per hour on a long run?

For runs and races longer than 90 minutes, sports dietitian Stevie Lyn Smith recommends 60 to 90 grams of carbohydrate per hour. The right amount within that range is the one you can tolerate without GI issues and execute on race day, so practice it on your long runs well before your race.

Who should I ask my running nutrition questions?

A registered dietitian who is board certified in sports dietetics (look for the CSSD credential) is the best person for running nutrition questions, especially anything involving bloodwork, iron, carb loading, or body composition.

How do I avoid burnout as a runner?

Build your year in seasons with different priorities, avoid stacking race after race, and take a break when you need one because fitness comes back. Also check whether you're eating enough, since underfueling can amplify anxiety and low mood.

How should I carb load for my first marathon?

Stevie recommends that newer marathoners practice a one-day carb load before three long runs during the training block and write down what they ate and how they felt. That way, race week is about following a proven plan instead of scrambling.

What are the new ferritin guidelines for iron deficiency?

In September 2026, the American Society of Hematology raised its ferritin thresholds for diagnosing iron deficiency to 30 ng/mL or below for most adults, with higher cutoffs for higher-risk groups. These are diagnostic thresholds, not optimal athlete targets, so read ferritin alongside a full iron panel and CBC.

Is it safe to lose weight during marathon training?

Stevie and Amanda both advise against weight loss goals during a marathon training cycle, because a caloric deficit works against training adaptations, recovery, and health. If body composition changes are appropriate, save them for the off-season and work one on one with a sports dietitian.