Let’s get one thing straight: keto isn’t some miracle diet or magic bullet—it’s just a tool.
A strong one, sure. But like any tool, it works best when used for the right job, at the right time, by the right person.
Some runners thrive on it for years. Others? Not so much.
I’ve seen both sides firsthand through coaching. I’ve worked with runners who used keto to drop serious weight, rebuild their aerobic base, and reclaim control of their energy. Then, when they needed that extra kick—say, during race season—they shifted to targeted or cyclical keto. That meant staying low-carb most of the time, but bringing in carbs when it mattered—before races or after brutal training days.
That’s what metabolic flexibility looks like: your body learns to burn fat efficiently but can still tap into carbs when needed.
I fall into this camp myself. I stay low-carb most of the time because I love the mental clarity, the even energy, and honestly, staying lean. But if I’m about to hammer a long run or toe the line for a race, I’m not afraid to throw down some rice or pop a gel. My body bounces back into ketosis pretty fast.
That’s the payoff—you’re no longer chained to carbs.
But here’s the honest truth: strict keto can blunt top-end speed.
Sprint work, high-intensity intervals, and all-out efforts rely heavily on glycogen, not fat.
As one runner said on Reddit (and I couldn’t agree more): “Keto hurts performance at faster speeds, but so does carrying extra weight.”
Trade-offs, always
You’ve gotta weigh it out. If your main goal is to race fast 5Ks or crush the track, you might perform better with more carbs. But if you’re targeting long endurance events or want to drop excess fat without feeling like a zombie, keto can be a smart play.
I’ve also seen big genetic differences—some runners adapt to fat like a machine. Others struggle, no matter how clean their keto game is.
And if keto doesn’t work for you? That’s fine. It doesn’t mean you failed.
Some folks just don’t feel great on it, even after the “keto flu” passes. Others can’t stand life without bread—and I get it.
Nutrition isn’t just about macros
It’s about quality of life, consistency, and your relationship with food.
If cutting carbs makes you miserable or kills your social life, then maybe a moderate low-carb approach is the better path.
I’ve coached clients through both.
One guy started strict keto, dropped weight, but hit a wall during intervals. We pivoted to a whole-food, moderate-carb plan—enough fuel for training, without the rollercoaster crashes.
Another client stayed full keto and crushed their ultra. The difference? Context. Needs. Goals.
Metabolic flexibility is what I’m after with most athletes.
I want your body to be fluent in both languages—fat and carbs.
Going full keto for a few months can train your body to burn fat like a pro. Even if you bring carbs back later, you’ll probably hold onto that fat-burning skill.
That’s gold in long races when you’re trying to avoid bonking.
Just know that the longer you stay in ketosis, the more “sensitive” your body may get to carbs. Some folks report that after months of keto, reintroducing carbs hits them harder—higher blood sugar spikes, a foggy brain, that kind of thing.
Not dangerous, just something to be aware of.
Personally, I like throwing in a higher-carb day every now and then—maybe once a week, or during a heavy mileage phase.
It’s part mental (feels like a relief), part physiological (keeps my body responsive to carbs), and part social (yes, I still want to enjoy a pizza night once in a while without guilt).
Here’s what I always tell clients:
Keto isn’t a lifestyle you have to commit to forever
It’s a tool.
Use it for fat loss, energy balance, metabolic control, or base building. Then switch tools when needed.
If you’ve got a race coming up, you might want to do a proper carb-load and fill up that glycogen tank.
If you’re vegetarian or have metabolic issues that make high fat tricky, maybe keto’s not your jam. And that’s totally okay.
As a coach, I’ll never push keto as the only answer. But I’ll say this: trying it taught me a lot.
I realized I didn’t need constant sugar bombs to train or function. I learned what it feels like to run on fat—steady, clear, unshakable. I also learned that carbs are still a damn powerful tool when used right.
Keto made me a better athlete and a more balanced coach
Not because it’s magic. But because it forced me to understand fuel—not just food.
What about you?
Have you ever experimented with keto? Did it work for your running, or did it flop?
Let’s talk about what fuel mix actually helps you feel and run your best.