Running to Burn Fat: The Go-To Guide for Fat-Adapted Running🏃

Running to burn fat isn’t just about weight control—it’s about optimizing how your body fuels every run 😉

When you exercise, your body burns a mix of fat and carbs—but cutting back on carbs flips the switch, making fat your primary fuel source. It takes patience but once you’re “fat-adapted,” you’ll unlock next-level endurance, steady energy, and faster running paces. Why settle for quick-burning carbs when you can run longer, stronger, and burn fat for energy?🔥💪

This is challenging and you may have to rethink your approach, but tweaks to your diet and training make it entirely doable, just takes a little time and if you enjoy experimenting well, this might be the challenge you've been looking for! 

Here’s what you’ll learn:

• The myth about the "fat-burning zone”
• How diet affects fat metabolism and energy use
• The truth about dietary fat, cholesterol and heart health—supported by research
• 4 diet strategies for fat-burning
• Why fat burners can still excel at speedwork (Volek et al., 2015)

In a nutshell, running to burn fat does not mean you have to cut carbs completely, but to reduce carbs strategically. By experimenting for a few weeks, you might find your running feels just as good—or better—but your primary fuel will be fat because that is what’s available as fuel in your body. Make sense?

Cool.

Think of these dietary adjustments as performance-enhancing tools, adding valuable assets to your running itinerary and, importantly – adding strength to your running foundation; so, let’s get started…

The “Fat-Burning Zone” and Why Runners Still Struggle with Weight Control

Have you ever heard that low-intensity running keeps you in the magical "fat-burning zone"? Spoiler: this is a running myth that has stuck like gum to a treadmill belt. Science tells a different story—fat loss comes down to total calories burned, not sticking to a mythical heart rate zone 😉

Yes, slow runs burn a higher percentage of fat, but the absolute amount of fat burned increases as you run faster. Running harder burns more overall calories, translating to more fat loss—even if carbs are your primary fuel at high intensity. Translated: more effort = more energy burned = more fat burned 🔥

OK then, we've established that running at low intensity doesn't mean you will burn more fat overall; we've also established we need to eat more fat to make the body prefer fat to carbs, but what about cholesterol?

Isn't high-fat supposed to be bad for you?

I hear you, but fat isn’t the enemy here...

Modern research has outdated the belief that dietary fat is harmful. Studies like Siri-Tarino et al., 2010, for example, found no significant link between saturated fat intake and heart disease. While LCHF diets may increase LDL cholesterol, they also raise LDL particle size, reducing heart disease risk. Additionally, low-carb, high-fat diets (LCHF) boost HDL which is the “good” cholesterol which lowers triglycerides, essential for heart health (Volek et al., 2008). Conversely, high-carb diets rich in refined carbs are linked to insulin resistance and chronic diseases (Ludwig et al., 2018; Hall et al., 2015)

LCHF diets reduce inflammation and improve metabolic health (Forsythe et al., 2008) - maybe it is time to rethink fat as not the enemy and that running to burn fat is not only good for your performance but also overall health.

How Carbohydrates Affect Fat Metabolism (and Why Insulin is the Boss)

When you eat carbs (sugars or starches), they break down into glucose, raising blood sugar and triggering insulin release. Insulin distributes glucose to muscles and the liver, storing any excess as fat. Similarly, fats break into fatty acids, which are used immediately or stored for later. Proteins become amino acids, essential for tissue repair and usable as energy if carbs and fats run low…

Insulin vs. Glucagon: The Hormonal Balance

Insulin is like a very strict “Goods In” manager at a warehouse, storing carbs while sidelining glucagon, the all-important fat-burning hormone. Glucagon, the "Goods Out" supervisor, signals the liver to burn stored fat through lipolysis but when insulin is in charge, glucagon can’t do its job...

The key is cutting carbs to lower insulin, allowing glucagon to kick fat-burning into high gear. Add some strength training, and you’ll even see some muscle definition. Your runs will burn stored fat as long as you train consistently. So, embrace a LCHF diet, let glucagon take charge, and utilise fat to fuel your training; be the best athlete you can be and fulfil your potential 😉🏃‍♀️

4 Diet Strategies: Running to Burn Fat

Here are four tried-and-tested diet strategies to fuel your runs—pick your level of commitment (and craziness):

1. Moderate-Carb Diet (100–150g/day): Enjoy carbs like rice and fruit while still boosting fat metabolism—great for runners in training but not ready for full keto (Hall et al., 2015)
2. Low-Carb Diet (50–100g/day): Cut back on starchy carbs while keeping protein, veggies, and healthy fats for better endurance and weight management (Westman et al., 2007)
3. Ketogenic Diet (<50g/day): The ultimate fat-burning plan for endurance athletes. Commit fully, and after 4-6 weeks, you’ll be fat-fueled and ready for anything! (Volek et al., 2015)
4. Carnivore Diet (Zero-Carb): Go primal with an all-meat diet for fat-burning, endurance, and mental clarity. Be mindful of nutrient gaps (Smith, John, et al., 2021). But if you're a true experimenter, then check out the Lion Diet by Mikhaila Peterson. 🥩🔥

Pick the strategy that fits your goals, timeline, and adventurous spirit— try the keto option (my personal choice) - you can always switch to another diet if it doesn’t work out for you. Try it for 4-6 weeks and see what happens…

A word about keto

Ketones are energy-rich by-products of fat burning, fueling the heart, muscles, and brain. While glucose is often considered essential, ketones become the superior energy source, especially during fasting or low-carb intake. This adaptation explains how humans survive without food, relying on stored fat for long periods (Cahill, 2006)

The ketogenic diet maximizes fat-burning by reducing carb intake to below 50g/day, forcing your body to use fat for fuel and, as a result, produce ketones into the blood which are octane fuel, as far as your body is concerned and the preferred fuel to glycogen. This abundance of ketones minimizes glycogen reliance, making keto an excellent choice for endurance athletes and those seeking real weight loss (Volek et al., 2015)

However, the ketogenic diet demands monk-like commitment—one carb binge will derail your progress as your body makes a grab for the glycogen in the blood instead of ketones. However, using a blood ketone meter, it is easy to determine whether you are in nutritional ketosis (between 1-3 mmol/L) and if you train in this state then your running performance will benefit profoundly. At least that was my experience...

Still with me? Great!

Bottom line: If you’re a serious runner, marathoner, or ultra-runner, keto isn’t just a diet—it’s the ultimate endurance game called “go insane,” fitness in expert mode. And mastering nutritional ketosis can and will elevate your performance - running to burn fat on steroids…

Like I said, give it a try. If after 4-6 weeks it's not working for you, try something else…

Can You Still Do Speedwork on a Low-Carb Diet?

Absolutely!

While high-intensity runs rely on glycogen, fat-adapted athletes can still excel. Research shows ketogenic runners oxidize fat 2-3 times faster than their carb-loaded counterparts, reducing glycogen dependence during tough workouts (Volek et al., 2015). While full keto-adaptation maximizes fat-burning, even moderate-carb intake (100-150g/day) supports endurance and speedwork by preserving glycogen and promoting fat oxidation; remember, it’s only about improving the ratio of running to burn fat vs carbs. This dual-fuel approach boosts performance while keeping carb-burning in check…

Why Fat Adaptation Works: (In a Nutshell)

1. Increased Fat Oxidation: More fat burned, even at higher intensities (Volek et al., 2015)
2. Glycogen Sparing: Keeps glycogen in reserve for sprints and bursts of speed (Phinney et al., 1983)
3. Dual-Fuel Flexibility: Seamless switching between fat and glycogen when needed (Lambert et al., 1994)

The research shows that while switching to a LCHF diet might cause a temporary performance dip, fat-adapted athletes can still crush high-intensity workouts, performing just as well as their carb-loaded competitors...

So, fat adaptation is an upgrade, not a slowdown. Your body taps into fat reserves while saving glycogen for sprints and intervals, ensuring steady energy, enhanced metabolic flexibility, and peak performance during high-intensity runs—a win for endurance and speed 💨👟

The Takeaway (With a Side of Fat-Burning Wisdom)

Skip high-carb diets—they’re like energy roller coasters you didn’t sign up for. Low-to-moderate carb eating means stable energy, faster recovery, and a fat-burning engine that won’t quit. And…

… by cutting down on foods like beans, dried fruit, apples etc., research shows that many people find bloating and flatulence greatly reduced (Dr. Berg, 2024) – you could say that your fat-burning strategy leads to "low carb-emissions,” and this helps to save the planet!🚫🍞 (apologies in advance)

My recommendation is to pair running and the keto diet for optimal results. It’s challenging at first, but once fat-adapted, sugar cravings fade, energy stabilizes, and you’ll look lean and fit. Whether aiming for performance or weight loss, keto delivers—just follow the science. Read The Art and Science of Low Carbohydrate Performance for expert tips. 💪📚

If you feel there’s no need for strict keto, just lower carbs to boost fat-burning. A low-carb (under 100g) or moderate-carb (100-150g) diet still trains your body to burn more fat than carbs and offers greater flexibility.

Ready to give it a go? Running to burn fat?

You've got this!

And if it doesn’t work... blame Julie  👉

Good luck and enjoy the journey!

Andy

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