Why Keto Slows You Down—Even If You’re a “Fat-Burning Machine”
Estimated read time: 4.2 minutes (about as long as it takes me to realize I forgot my gels on a long run). 😉
Hey Performance Nerds! Jonah here. 🤓
Becoming a fat-burning machine sounds great, until it slows you down.
I used to believe keto could help runners. I was wrong. Here's what changed my mind.
Today you'll learn:
Why becoming a "fat-burning machine" can sabotage your speed
The performance cost of training your body's engine wrong
My new carb-focused approach (and why it's working)
Exact fueling targets that optimize both training and recovery
(Augie, my dog, has been on the "whatever-falls-on-the-floor diet" his whole life. Somehow he's still faster than me on easy runs.)
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🏃♂️ Keto’s Big Lie: Why Fat-Burning Slows You Down
The pitch sounded perfect: become a fat-burning machine, spare your precious glycogen stores, and never bonk again.
But Dr. Louise Burke's "Supernova" studies crushed that dream.
The keto athletes became incredible fat-burners. But their performance tanked. They needed more oxygen to run the same pace.
Translation: they got worse at going fast.
Becoming more efficient at using slower fuel made them less efficient overall.
It's like training your Ferrari to run on diesel. You'll get better at using diesel, but you just lost your top-end speed.
⚡ Why Carbs = Your Speed Gear
Here’s the science in one line: Carbs deliver 8% more energy than fat per oxygen molecule.
Over 26.2 miles, that’s the difference between a PR and a death march.
Dr. Tim Podlogar puts it plainly:
“Focusing on carbs is the most important thing” for performance athletes.
Keto's fatal flaw: High-fat diets downregulate your body's ability to use carbs at high rates. You lose your "top gear": no more surges or final kicks.
What actually separates elite runners? VO2 max and superior fitness, not fat-burning efficiency. They burn more fat because they're fitter, not because they restricted carbs.
We shouldn't chase fat oxidation: that won't make you faster.
Train for fitness. Fuel with carbs. Adapt like an athlete.
💪 Carbs Help You Recover Harder, Not Just Run Faster
You know what carbs also do? They optimize recovery.
Research shows athletes who eat sufficient carbs can: “Sustain day out, day in a lot of exercise.”
Better recovery means:
Train more often
Hit harder sessions when it counts
Bounce back faster between workouts
Recover better so you can handle more volume
More volume = stronger adaptations = faster running
Since I shifted to carb periodization, my recovery improved, my session quality went up, and I’m handling more weekly volume because I'm actually recovering between sessions.
Research backs this: carbs improve recovery based on training demands. Fat doesn't. Vary carbs daily, keep fat consistent.
✅ Carb Periodization Cheat Sheet (with Daily Targets)
You don’t need to eat pasta all day, every day. (Augie and I still think about it.)
You need to fuel the work you’re asking your body to do.
My simple approach: Keep fat and protein consistent. Vary carbs based on training.
🧱 Daily Foundations (Keep These Consistent)
Protein: 1.6–2.0g/kg bodyweight (0.73–0.9g/lb)
Crucial for muscle repair and recovery
Hit it every day, no matter what
Fat: ~1.0g/kg bodyweight (0.45g/lb)
Supports hormones and nutrient absorption
Stay consistent regardless of training load
📈 Vary Your Carbs Based on Training Load
🔐 The trap to avoid: Under-fueling long, slow runs to “burn more fat.”
That usually backfires:
Poor recovery
Overeating later
Garbage sessions the next day
⚡ TL;DR – Strategic Carbs > Metabolic Tricks
Key takeaways:
Keto boosts fat burning, but tanks speed (thanks, Supernova)
Carbs give you 8% more energy per oxygen molecule: you’ll need that on race day
Fuel your work, not your ego: Carb periodization = higher performance + better recovery
Elite runners adapt with carbs, not restriction
Keto can build muscle and endurance, but it's not optimal for high-volume athletes chasing peak performance.
I swapped low-carb for high-performance fueling. Training got better. Recovery got faster. Adaptations got bigger.
Bottom line:
Stop chasing fat adaptation.
Start fueling your work.
That’s what makes you faster.
💬 One last thing before you go.
After the NFL, I wasn’t sure if obsessing over performance science still mattered—until I started helping this community.
Your training goals? They brought that fire back.
So if you're feeling stuck, second-guessing something, or just want to share how training's going—hit reply. I read every message, and I’m here to help however I can.
🚨 New research on 5,200 runners just added important nuance to what drives injury risk
Did you miss my post about New research on 5,200 runners just added important nuance to what drives injury risk? You can find it below!
I won’t lie. These posts take me a while to make. If you find it helpful, share it on your story or with a friend. It helps me a ton!
Are You a True Running Nerd? Prove it.. 🧐
Welcome to the prove you’re a nerd section. Each week, I ask a question about a common running science myth.
Answer correctly, and you’ll be entered into a weekly raffle to win a package of Jonah’s favorite supplements.
What does it mean if your HRV drops and gets more up-and-down than usual during a hard training block?
(One low HRV day isn’t a crisis. But trends over several days—especially if HRV gets more up-and-down—can signal real strain. And yes, wearables aren’t perfect, but they’re useful when you track consistently.)
Last Week’s Results: Gel Early, Go Long 🍯🏃♂️
Gels aren’t just for marathoners and most of you nailed it. But there’s still confusion around how short is too short to bother with mid-run carbs.
The correct answer?
A. Half marathon or longer (≥75 min) 🍯🏃♂️ ✅
Research shows that endurance performance improves when you fuel during efforts lasting 75 minutes or more, even in a half marathon.
Carbs help spare liver glycogen, sustain pace, and keep your brain sharper in the back half. If your race is over an hour and you're working hard, fueling is a smart performance tool.
Here’s how the votes shook out:
🟩 A. Half marathon or longer (≥75 min) – 197 ✅
🟨 B. Marathon only (2–3+ hours) – 35
🟨 C. 10K and up (≥45 min) – 76
🟨 D. All races – 74
What about shorter races?
For efforts under 75 minutes, research shows mid-run fueling doesn’t help much—as long as you're properly carbed up going in. Your glycogen stores can cover that duration.
That said, there’s one trick worth knowing. Swishing (not swallowing) a carb drink for 5–10 seconds has been shown to maybe improve performance by 2 to 3 percent in hard efforts under an hour. It works by sending “fuel is coming” signals to the brain, not the muscles. No gut load required.
Bottom line?
Once your race crosses the 75-minute mark, fueling mid-run goes from optional to essential. Practice it just like pacing or hydration. 🍬🧪
Don’t forget: You + Science = AWESOMENESS 😎
Yours in science,
Jonah
P.S. - We have a crew of 17,230+ nerds here who are running FAST using science.
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