Carnivore Diet: 16 Common Myths Decoded by Biology

# Carnivore Diet: 16 Common Myths Biology Forces Us to Rethink

**by Laurent Glatz – for Athletic Carnivore**

The carnivore diet destroys kidneys. It clogs arteries. Without fiber, the gut stops working. Without fruit, scurvy sets in. Without sugar, you can’t exercise. Red meat causes cancer.

Hearing these phrases repeatedly, they eventually become more than hypotheses. They become certainties.

And that’s precisely where the problem begins.

Because in nutrition, a statement can seem perfectly logical, be based on a real biological mechanism, yet become false when turned into a universal rule.

This happens very often with the carnivore diet.

We observe a mechanism. Then we jump straight to the conclusion.

Proteins increase kidney filtration? Therefore, they destroy kidneys.

Saturated fats can raise LDL? Therefore, they clog arteries.

Certain gut bacteria use fiber? Therefore, without fiber, the microbiome collapses.

Meat contains purines? Therefore, it causes gout.

Each argument contains a kernel of truth.

But a kernel of truth is not yet proof.

The First Trap: Confusing Adaptation with Disease

Let’s take the kidney.

When protein intake increases, kidney filtration can increase. This phenomenon exists.

But an increase in filtration does not automatically mean damage is occurring.

In adults without chronic kidney disease, available trials do not show that high protein intake inevitably leads to kidney deterioration. Our video script notably reviews a meta-analysis of 22 randomized trials that found no consistent biochemical signal of kidney damage in this population.

That doesn’t mean all situations are identical.

A person with pre-existing kidney disease obviously cannot be reasoned about the same way as someone with healthy kidneys.

And above all, it reminds us of a crucial point: before blaming a diet, you must know exactly which diet you’re talking about.

A carnivore diet rich in lean meats does not have the same composition as one including fatty cuts, eggs, fish, marrow, or other animal sources.

Carnivore does not automatically mean hyper-protein.

This simple distinction already changes much of the debate.

Second Trap: Turning a Capacity into an Obligation

Humans are omnivores.

That’s true.

But that means they can utilize both plant and animal resources. It does not mean they must consume both constantly.

This is a fundamental difference.

The ability to metabolize a food does not prove it is indispensable.

Humans can use starch. They can use fructose. They can ferment certain fibers thanks to their microbiome.

But none of these observations alone prove that a daily portion of these foods is necessary.

The script clearly reminds us: our most remarkable trait is probably our dietary flexibility. Depending on environments, human populations have relied very differently on plant and animal resources.

It is therefore a mistake to turn the label “omnivore” into an automatic verdict against any predominantly animal-based diet.

Fiber Perfectly Illustrates the Limits of Slogans

“No fiber means constipation.”

This statement is repeated so often it seems almost obvious.

Yet the data are less straightforward.

A study on people suffering from chronic idiopathic constipation observed that after reducing or eliminating fiber, a significant portion reported a clear improvement in symptoms.

In the group maintaining zero fiber, stool frequency improved and symptoms like constipation, bloating, abdominal pain, or straining during defecation disappeared in participants reported in this study.

This obviously doesn’t mean everyone should eliminate fiber.

It demonstrates something far more interesting:

Fiber is not automatically the solution for everyone.

For some, increasing fecal bulk can help.

For others, more bulk and fermentation can increase discomfort.

The same advice can therefore produce two different responses.

And this is precisely where generic advice begins to show its limits.

Does the Microbiome Collapse Without Fiber?

Again, the mechanism seems simple.

Fiber feeds certain bacteria.

Therefore, without fiber, the microbiome should collapse.

But a recent human study on people following a carnivore diet for several years did not observe a global collapse of microbial diversity.

Alpha diversity was not significantly lower, and bacterial richness measured by the Chao1 index was even higher in the carnivore group studied.

That doesn’t mean the microbiome remains the same.

It changes.

And that is precisely the important nuance.

A different microbiome is not automatically a destroyed microbiome.

Again, we see the same problem: turning a biological change into disease before demonstrating that this change actually causes harm.

The Brain Needs Glucose. Not Necessarily Dietary Sugar.

Another classic phrase:

“The brain needs sugar.”

The brain indeed uses glucose.

But that doesn’t mean consuming sugar is mandatory to supply it.

The liver can produce glucose via gluconeogenesis from several substrates, including lactate, glycerol, and certain amino acids.

When carbohydrate intake drops sharply, ketone body production also rises, and these become an important energy source for the brain.

The body needs glucose.

But needing glucose does not mean a constant need for dietary sugar.

This confusion between a necessary molecule and a necessary food is probably one of the most frequent errors in nutrition debates.

The Same Reasoning Applies to Exercise

Can you exercise with very little dietary glucose?

Yes.

Can you build muscle without consuming much sugar?

Yes, as well.

Muscle builds with mechanical stimulus, amino acids, energy, and sufficient recovery.

A meta-analysis mentioned in the script found no significant advantage of higher glucose-providing food intake on hypertrophy when protein intake was comparable.

But that doesn’t mean glucose is never useful.

When intensity is very high, sets follow one another, recovery is short, and glycolytic efforts repeat, muscle glycogen can become important to maintain power and training volume.

The nuance is essential.

Glucose can be a tool.

That doesn’t mean it’s required all day long.

And it doesn’t mean it’s useless either.

Cholesterol, Cancer, Gout: The Same Problem Recurs

Saturated fats can raise LDL in some people.

Yes.

But an LDL increase is not synonymous with an artery instantly clogging.

Atherosclerosis is a complex process involving exposure to ApoB-containing particles, blood pressure, smoking, blood sugar, insulin resistance, age, genetics, and other factors.

The same goes for red meat and cancer.

There are observational associations, notably with colorectal cancer.

But association is not automatically proof of causality.

Lifestyle habits, smoking, alcohol, physical activity, ultra-processed foods, or cooking methods can also differ between studied groups.

The same logic applies to gout.

Meat contains purines.

But uric acid also depends on endogenous production, renal excretion, insulin, alcohol, fructose, and overall metabolic context.

What these examples show is not that everything is false.

They show that almost nothing is as simple as slogans suggest.

The Real Risk: Applying a General Rule to a Specific Individual

This is probably where the subject becomes most important.

Two people can follow a carnivore diet and have different responses.

One may experience excellent satiety, weight loss, and improvement in some markers.

The other may suffer persistent fatigue, poor digestive tolerance, decreased performance, or significant changes in lipid profile.

That is not enough to say carnivore “works” or “doesn’t work.”

It means the response depends on the individual’s biology.

Dietary history.

Sleep.

Stress.

Digestion.

Tolerance to different animal sources.

Athletic level.

Recovery.

Metabolic context.

The danger of generic advice is therefore not only that it can be wrong.

It can be true but applied to the wrong person, at the wrong time, or for the wrong reason.

And that’s often how one starts changing one parameter, then another, then a third, until no one knows what really improved the situation.

The real cost then is not just lost time.

It’s the risk of correcting the wrong variable.

What Science Can Really Tell Us Today

Human literature directly dedicated to the carnivore diet remains limited.

A review published in 2026 identified only nine human studies meeting its criteria.

These data do not allow us to claim the carnivore diet is definitively dangerous.

Nor do they prove it is automatically optimal for everyone.

This is probably the most interesting position.

The carnivore diet doesn’t need defending against science.

It needs to be properly studied.

With humans.

For sufficiently long durations.

With a precise definition of what is actually consumed.

And above all, we must stop believing that an isolated mechanism is enough to describe what happens in an entire organism.

At this stage, the real question is no longer simply: “Is the carnivore diet good or bad?”

The question becomes much more personal:

**How does your own body respond to what you are asking of it today?**

Because accumulating even more general rules won’t necessarily tell you which one fits your situation.

Sometimes what’s missing isn’t more information.

It’s a more precise reading of your own biology.

**CTA: Understand My Metabolic Terrain**

And you: are you still searching for the right universal rule, or are you beginning to understand that your response may depend mostly on your own functioning?

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