Cardio, Low Carb, and Carnivore: Understanding Their True Link to Weight Loss

# Does Cardio Really Make You Lose Weight? The Question Becomes Much More Intriguing on Low Carb or Carnivore

**by Laurent Glatz – for Athletic Carnivore**

You step onto a treadmill, pedal for an hour, or take a brisk walk by the water. Your body needs to produce ATP to fuel your muscles. It can use several fuels, mainly carbohydrates and fats.

This is where a low carb or carnivore diet fundamentally changes the context.

Because if you drastically reduce carbohydrate intake for a sufficient period, your body can no longer operate exactly like someone who consumes several hundred grams of carbs daily.

It adapts.

It increases its capacity to mobilize and oxidize fats.

And when you combine this adaptation with prolonged aerobic exercise, you effectively get something that looks much more like a **physiological machine geared toward fat utilization**.

But it’s crucial to understand precisely what this means.

Burning a lot of fat during a session and losing a significant amount of body fat are not exactly the same thing.

What Changes When Carbohydrates Become Scarce

In someone who regularly consumes a lot of carbohydrates, muscle and liver glycogen stores play a major role during exercise.

Blood glucose and muscle glycogen fuel glycolysis, and depending on intensity, some of the pyruvate produced enters the mitochondria to help generate ATP.

When dietary carbohydrates drop sharply, the body faces a different metabolic environment.

Basal insulin tends to decrease.

Mobilization of fatty acids from adipose tissue becomes more accessible.

The liver increases ketone body production when conditions allow.

Most importantly, with adaptation, muscles significantly boost their ability to oxidize fatty acids during exercise.

This is not a carnivore theory.

It is experimentally measured.

A recent systematic review and meta-analysis on low carb and ketogenic diets in trained athletes reported that **all 30 studies measuring fat oxidation observed an increase**, ranging roughly from +28% up to +200%, depending on protocols and populations.

Earlier studies on keto-adapted athletes also observed fat oxidation rates reaching about **1.5 grams per minute**, values considerably higher than those typically seen in athletes on high-carb diets.

This is the real metabolic advantage.

You haven’t just removed sugar from your plate.

You have progressively changed **the fuel your muscles become capable of using extensively**.

Cardio Then Becomes Particularly Interesting

During relatively long, low to moderate intensity activity, ATP production can largely rely on oxidative metabolism.

And oxidative metabolism is perfectly suited to using fatty acids.

In someone adapted to low carb or carnivore, this capacity can become remarkable.

A brisk walk.

A hike.

An easy jog.

Cycling.

A relatively long session at controlled intensity.

This type of activity creates an energy demand compatible with a significant contribution from lipids.

Unlike glycogen, whose body stores are limited, adipose tissue energy reserves are immense.

Even a relatively lean person has tens of thousands of kilocalories stored as fat.

This is where the expression “fat-burning machine” takes on real physiological meaning.

Not because the body turns into a magic furnace.

But because an organism adapted to low carbohydrate availability becomes capable of producing a much larger proportion of its energy from fats during exercise.

But Beware: Burning Fat Doesn’t Automatically Mean Losing Fat

This is probably the most important nuance in the entire article.

If your body oxidizes a lot of fat during two hours of cardio, that fat has to come from somewhere.

It can come from adipose tissue.

But it can also partly come from the fat you just ate or triglycerides stored in muscle.

What determines long-term reduction of fat stores is therefore the **overall lipid balance**, not just the oxidation rate measured during your run.

A highly controlled metabolic experiment clearly demonstrated this: drastically reducing carbs does increase fat oxidation, but when energy intake is controlled, it doesn’t necessarily mean more body fat is lost compared to other macronutrient distributions.

That’s why we must distinguish two statements:

**Low carb increases the capacity to use fat as fuel: yes, very clearly.**

**Low carb automatically guarantees fat loss regardless of everything else: no.**

This distinction makes the approach more credible, not less interesting.

Where Low Carb Can Become Especially Powerful: Satiety

Cardio doesn’t act in a vacuum.

If an hour of exercise increases your energy expenditure but you come home ravenous and immediately consume a lot of energy, part of the energy benefit disappears.

A diet based on animal foods rich in protein, low in ultra-processed foods, and low in carbohydrates can completely change this behavioral equation.

Proteins have a powerful satiating effect.

A carnivore diet also eliminates many foods that combine fat, starch, sugar, flavors, and highly rewarding textures simultaneously.

And this difference can become essential.

Because success in a fat loss program depends not only on energy spent during exercise.

It also depends on what your brain drives you to eat afterward.

This is where cardio and low carb can become particularly complementary:

**increasing the capacity to expend energy while operating in a dietary environment that potentially facilitates satiety.**

But Why Does Your Brain Accept Functioning Without Massive Carb Intake?

Because another myth must fall: removing dietary carbs does not mean eliminating glucose from the body.

Your body knows how to make glucose.

The liver, and to a lesser extent the kidneys, use **gluconeogenesis** to produce the glucose needed by certain tissues.

Lactate.

Glycerol from triglycerides.

Certain amino acids.

All can serve as substrates.

At the same time, when carbohydrate availability is sufficiently low, the liver produces more ketone bodies from fatty acids.

These ketones cross the blood-brain barrier and can supply a significant portion of the brain’s energy needs.

This doesn’t mean the brain stops using glucose entirely.

It still needs some.

But a considerable part of its energy requirements can shift to ketone bodies.

In other words, absence of dietary carbs and absence of blood glucose are two completely different things.

Glycogen Has Not Disappeared

Here the discourse must remain extremely precise.

Some portray the carnivore diet as if glycogen becomes useless.

This is false.

As intensity increases, carbohydrates become metabolically very important.

Why?

Because they allow rapid ATP production with better energy efficiency per oxygen unit than fatty acids.

During a sprint, a very intense HIIT session, repeated accelerations, or an effort near maximal aerobic power, glycolysis and glycogen become much more important.

Recent data show that low carb/ketogenic diets significantly increase fat oxidation while potentially impairing some repeated high-intensity efforts.

It’s therefore a mistake to expect fat to do exactly the same work as glucose.

They don’t play the same role.

For a relatively long, controlled endurance outing, the huge energy availability from fats is a clear advantage.

To produce a sudden burst of power, glycogen remains fundamental.

And that’s precisely why **the type of cardio matters as much as the diet**.

Carnivore Mainly Transforms the Fuel Question

Imagine two athletes running side by side at the same pace.

The first consumes a lot of carbohydrates daily.

The second has been adapted for weeks or months to a very low carb diet.

Their heart rates might be similar.

Their speed might be identical.

But their mix of energy substrates can be very different.

The second can oxidize much more fat at the same intensity.

This is a true metabolic adaptation observed in the literature.

And this capacity becomes particularly interesting when the goal isn’t to break a 400-meter record but to develop:

- endurance,
- oxidative capacity,
- metabolic flexibility,
- regular energy expenditure,
- and potentially fat tissue reduction.

What About Fasted Cardio?

Again, the combination becomes biologically interesting.

After a night without eating, insulin is generally lower and free fatty acid availability is higher.

Studies show that performing aerobic exercise fasted generally increases fat oxidation during the session compared to exercising after a meal. This phenomenon is real.

In someone already adapted to a low carb or carnivore diet, you potentially add two environments favoring fat use:

- chronic low carbohydrate availability,
- plus acute lower nutritional availability before exercise.

It’s easy to understand why fat oxidation can become very high.

But again: **more fat oxidation during that hour doesn’t automatically guarantee more body fat loss over several months.**

Your body will then do its overall balance.

Outdoors, by the Sea or in the Forest?

Here the topic becomes even more interesting.

Physiologically, at equal intensity and energy expenditure, running in a forest doesn’t have a mysterious property that doubles fat use compared to a treadmill.

Studies comparing indoor and outdoor exercise don’t clearly show acute metabolic superiority outdoors when intensity is matched.

But they show something else: the subjective experience is often better outside.

Greater pleasure.

More positive affect.

Better psychological state in several studies.

And that matters a lot.

Because a perfect hour of cardio done three times then abandoned is worth much less than a slightly less “optimized” activity you do spontaneously all year round.

The seaside, a forest, or a mountain can therefore have an extremely powerful indirect advantage:

**they can make movement easier to maintain.**

And consistency eventually weighs far more than optimizing a single session.

Mountains Even Mechanically Change the Equation

A hike with elevation gain isn’t just walking on a treadmill with a nice view.

The slope increases energy demand.

Uneven terrain changes muscle recruitment.

Downhill adds a strong eccentric component.

Altitude can alter oxygen availability.

Temperature influences thermoregulation.

Outdoor cardio can therefore become physiologically very different from indoor cardio.

And this is especially interesting for someone primarily using fat as fuel: a long submaximal activity can represent several hours of significant fat oxidation without necessarily imposing the same glycolytic demands as very intense training.

This Is Where Carnivore Can Become a True Metabolic Strategy

Not because it breaks thermodynamics.

Not because ketones magically melt fat.

But because it can simultaneously modify three fundamental parameters:

- available fuel,
- muscles’ capacity to oxidize fats,
- and potentially hunger regulation through a diet very high in protein and low in hyperpalatable foods.

A properly adapted person can thus perform a large amount of aerobic work using a huge amount of fat.

A recent meta-analysis shows that low carb diets consistently increase fat oxidation in studied athletes, even if performance effects depend on intensity and context.

And this probably sums up carnivore’s interest for cardio much better:

**it doesn’t make energy free; it changes how your body sources it.**

But One Last Mistake to Avoid

You might read all this and conclude:

"Perfect. I’ll cut all carbs, do two hours of fasted cardio every morning, and become a fat-burning machine."

That would be precisely the opposite mistake.

Because training remains a stress.

If your volume exceeds your recovery, if your sleep deteriorates, if your protein or energy intake becomes insufficient, if your muscle mass starts to decline, or if your daily activity collapses because you’re constantly exhausted, increasing cardio further can become counterproductive.

Recent sports performance science confirms that low carb adaptation is highly context-dependent: fat oxidation increases dramatically, but high-intensity or repeated efforts may suffer when glycogen availability becomes limiting.

That’s why the real question isn’t just:

**"Am I burning fat?"**

The real question is:

**"What fuel is my body using, at what intensity, for how long, and what does this strategy cost it afterward?"**

This is where carnivore, low carb, and cardio can become extremely interesting together.

Not because they create a biological exception.

But because they can deeply steer metabolism toward using a fuel the body has vast reserves of: **fat**.

And when this capacity is combined with an activity you can repeat regularly, good muscle mass preservation, and a diet that truly controls your hunger, the discussion about fat loss becomes far more relevant than the simple number displayed on a treadmill.

**So, when you do your cardio today, do you really know if your body is operating mainly as a machine dependent on frequent carb intake, or as an organism already adapted to mobilize its own energy reserves?**

**Understanding My Metabolic Terrain**

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