Especially for those living with diabetes, it’s likely that you’ve been tempted to follow a ketogenic diet to lose weight, drop your A1c, and flatline your blood glucose.

Even though it may seem tempting to enter the metabolic state of ketosis, it’s important to understand the caveats of ketosis, so that you fully understand your risks for developing long-term complications.

So what exactly is a ketogenic diet? And why is ketosis a popular recommendation for those living with diabetes? 

A ketogenic diet a very low-carbohydrate diet by design, containing a maximum of 30 grams of dietary carbohydrate per day. 

When eating a ketogenic diet, you are told to avoid carbohydrate-rich foods like fruits, starchy vegetables, legumes, and whole grains, and instead eat larger quantities of meat, dairy, leafy greens, non-starchy vegetables, nuts, seeds, and vegetable oils. 

In order to achieve the state of ketosis, you are only allowed to eat a small amount of carbohydrate energy from fruits and starchy vegetables. 

The ketogenic diet explicitly prohibits the consumption of grain products (even whole grains), pasta, refined sugar, milk, corn, legumes (including lentils, beans, and peas), as well as rice.

When you eat a ketogenic diet, your muscle and liver switch from oxidizing glucose as their primary fuel to fatty acids as their primary fuel.

While this may seem like a “logical” approach to reducing blood glucose fluctuations, one significant problem with a ketogenic diet is that your brain cannot follow the lead of your liver and muscle by switching from glucose to fatty acids and amino acids.

Instead, your brain is designed to run off of glucose exclusively, and is therefore dependent on dietary carbohydrate for energy. In order to withstand a very low-carbohydrate intake, your liver manufactures ketone bodies as an emergency backup fuel for your brain when in the state of ketosis.

If you are living with diabetes, this may sound like a great idea, because your pancreas is provided with an opportunity to reduce insulin production due to low carbohydrate intake.

Millions of people around the world who eat a ketogenic diet, achieve a flatline blood glucose profile and greatly reduce or eliminate their need for oral medication and insulin.

If you have experienced this yourself, you may be thinking, “Great, I solved the problem. Eating a ketogenic diet is keeping my blood glucose in control, and therefore my diabetes health is going up.”

In addition, the state of ketosis induces a number of short-term benefits including rapid weight loss, reduced fasting glucose, reduced post-meal blood glucose, reduced A1c, reduced total cholesterol, reduced LDL cholesterol, and flatline blood glucose.

Medical professionals love seeing these biomarker changes, which tricks both patients and doctors into believing that ketosis is an excellent long-term dietary strategy.

The problem is that eating a ketogenic diet significantly increase your risk for chronic disease and premature death in the long-term, as you will read about in this article.

After researching the advice from the top ketosis gurus, we made a list of the 7 biggest (and most dangerous) misconceptions about ketogenic diets.

In this article, we’ll go into detail about the truth underlying ketosis, and refute many common statements backed by misleading science, incorrect biochemistry, and a fundamental lack of understanding of human biology.

You may have heard people in the ketogenic community refer to insulin as your “fat storage hormone,” and that by adopting a very low-carbohydrate diet, you prevent your blood glucose from “spiking” after a meal.

While there is some truth to this statement, it is absolutely crucial to understand that the primary function of insulin is to help transport glucose out of your blood and into tissues, and a secondary effect of insulin is to help transport fatty acids and amino acids out of your blood and into tissues.

Simply because insulin has the ability to transport fat into tissues, does not mean that it’s factually correct to label insulin as your “fat storage hormone” – this is a gross exaggeration of the actual role of insulin, and is meant to scare people into believing that any amount of insulin in circulation will make you fat.

It is important to understand that insulin is most effective at promoting glucose uptake, but also functions to promote fatty acid uptake and amino acid uptake into tissues. 

Open any biology textbook, and you’ll find that the primary function of insulin is to help glucose exit your blood and enter tissues, but that insulin also facilitates the movement of fatty acids and amino acids out of your blood and into tissues (1). 

Labeling insulin as your “fat storage hormone” is simply incorrect from a biological perspective.

Insulin triggers macronutrient uptake in this order:

Take a look at this infographic for a more detailed understanding of the insulin priority hierarchy.

Insulin is the most powerful anabolic hormone in your body (meaning that it promotes more growth and fuel storage than any other hormone), and ketogenic dieters exaggerate this fact, condemning insulin entirely, claiming that even small amounts of insulin will make you fat. 

The truth is that all mammals secrete insulin, because insulin is absolutely required for life.

In truth, a physiologically normal amount of insulin is required to stay alive, but secreting or injecting excess insulin is what substantially increases your risk for coronary artery disease, atherosclerosis, and cardiovascular disease as a whole (2–10).

Labeling insulin as your “fat storage hormone” not only misrepresents it’s true biological activity, it scares people into believing that insulin is the enemy, and even small amounts of insulin cause weight gain, obesity, and type 2 diabetes.

Proponents of the ketogenic diet often argue that eating any food containing carbohydrate energy will spike your blood glucose, and that the only way to avoid dangerous blood glucose spikes is to avoid carbohydrate-rich foods.

Technically speaking, when you eat carbohydrate-rich food, your blood glucose will rise. Furthermore, reducing your carbohydrate intake will keep your blood glucose more stable.

For these reasons, ketogenic dieters maintain a total carbohydrate intake of less than 30 grams per day, representing less than 10% of total calories on average.

What those in ketosis don’t understand is that the amount of glucose in your blood is not only determined by the amount of carbohydrate that you eat, but instead is a reflection of both your dietary carbohydrate intake AND your dietary fat intake (11–30).

We have written extensively about the detrimental role that excess dietary fat plays in the development of insulin resistance, leading to high blood glucose, increased insulin requirements, high cholesterol, beta cell death, and increased risk for many chronic diseases.

To understand how your blood glucose responds to different macronutrient profiles, let’s explore how a ketogenic diet, Standard American Diet (SAD), and low-fat, plant-based, whole-food diet affect your blood glucose.

Diet #1: Ketogenic Diet

Suggested carbohydrate intake: <10% of calories (<30 grams per day)
Suggested fat intake: 60-70% of calories
Suggested protein intake: 20-35% of calories

When operating in a high-fat ecosystem on a ketogenic diet, the primary reason why your blood glucose remains flat is because of the near absence of carbohydrate-rich foods. 

In this way, eating a high-fat diet is very effective at flatlining your blood glucose values because carbohydrates are kept below 30 grams per day. As long as you avoid carbohydrate-rich foods, your blood glucose will remain remarkably stable.

But the minute you chose to eat a carbohydrate-rich food (such as a banana, potato, or bowl of quinoa), your blood glucose is likely to increase significantly due to a hidden state of fatty-acid-induced insulin resistance.

For these reasons, those in ketosis often fail an oral glucose tolerance test, because their muscle and liver are incapable of metabolizing a carbohydrate challenge.

Diet #2: Standard American Diet (SAD)

Average carbohydrate intake: 40-45% of calories
Average fat intake: 40-45% of calories
Average protein intake: 15-20% of calories

Because both fat and carbohydrate are present in large quantities, controlling your blood glucose becomes increasingly difficult over time.

Diet #3: Low-Fat, Plant-Based, Whole-Food Diet

Suggested carbohydrate intake: 70-80% of calories
Suggested fat intake: 10-15% of calories (20-30 grams per day)
Suggested protein intake: 10-15% of calories

Because a low-fat, plant-based, whole-food diet is low in dietary fat, your carbohydrate tolerance (ability to eat carbohydrate-rich food) increases substantially, resulting in maximal insulin sensitivity, and the opportunity to completely reverse insulin resistance.

When operating in a low-fat ecosystem on a plant-based diet, it is quite easy to maintain flatline blood glucose as long as your total fat intake is maintained below 30 grams per day, and your carbohydrate intake comes from whole foods like fruits, vegetables, legumes, and whole grains and not from products containing refined sugars.

Those in the ketogenic community often label diabetes as a problem of “carbohydrate toxicity,” suggesting that dietary carbohydrate is the primary cause of the disease process.

In addition, ketogenic dieters believe that insulin resistance is caused by insulin itself, triggered by an excess consumption of dietary carbohydrate.

In order to make these statements factually correct, it’s necessary to go back to basic biochemistry principles and understand that the vast majority of people who develop insulin resistance do so by eating a diet containing large amounts of dietary fat.

The research world has known for more than 85 years that carbohydrate intolerance results from the overconsumption of fat. This was first established in the 1930’s by the pioneering work of Drs. Rabinowitch (31–34) and Himsworth (35), then further proven by Dr. Kempner (36) in the 1950’s, and by Dr. Anderson (37–39) in the 1970’s.

You can read all about those studies by clicking on the image below:

Despite this, the cause of insulin resistance and carbohydrate intolerance remains one of the most debated subjects in the world of diabetes even today.

The problem is that by labeling carbohydrate intolerance as a problem of carbohydrate toxicity rather than a problem of fat toxicity, most people are driven towards a low-carb diet to stop them from needing more oral medication and insulin over time.

Even though a high-fat, high-protein diet is very effective at reducing blood glucose fluctuations in the short term, many people become more insulin resistant over the course of years. In this respect, the short-term benefits do not accurately reflect the long-term consequences of eating a low-carbohydrate diet.

Think of insulin resistance as a series of metabolic dominoes. The dominoes are arranged in this order:

1. Eat excess dietary fat (greater than 15% of total calories)
2. Dysfunctional insulin receptors
3. Glucose becomes “trapped” in your blood, resulting in high blood glucose
4. Your need for oral medication and/or insulin increases

The problem is simple: if you talk about carbohydrate intolerance without talking about fat, you’re missing the bigger picture.

As I demonstrated in a recent lecture, how this works is that the consumption of excess fat blocks the ability of insulin receptors in your muscle and liver to allow glucose to exit the blood and enter these tissues. 

Glucose then gets trapped in the blood, resulting in high blood glucose and an increased need for insulin.

The ketogenic world is quick to point out that there is no such thing as an "essential carbohydrate,” in contrast to required nutrients like essential fatty acids and essential amino acids.

While this statement is technically true, labelling glucose as a "nonessential" carbohydrate implies that there is no use for glucose in the human body.

Once again, let’s return to basic human physiology in order to understand the truth.

Your muscle, liver, and other peripheral tissues are capable of oxidizing glucose, amino acids, and fatty acids for energy. Your brain, however cannot oxidize either amino acids or fatty acids for energy.

As a result, your brain must oxidize glucose on-demand, importing glucose from your blood 24 hours a day. Since glucose is your brain’s principal on-demand fuel, carbohydrate-rich foods are your brain’s primary fuel source.

When you consume a low-carb diet, you force your liver to synthesize an emergency backup fuel known as ketone bodies to prevent against brain starvation.

In this state, your brain is forced to adapt to a new emergency backup fuel, and you enter the state of ketosis in which ketone bodies are your brain’s principal fuel.

Ketogenic diets were originally invented for people with epilepsy, and are effective at reducing seizure incidence. However, ample evidence shows that ketogenic diets come with a laundry list of unwanted side effects that simply cannot be overlooked (40,41).

These side effects are chronic health conditions that are fueled by a diet low in carbohydrates, high in fat, high in protein, and low in micronutrients like vitamins, minerals, and antioxidants.

Side Effects of Ketogenic Diets

Most importantly, ample scientific evidence clearly shows that low-carbohydrate diets increase your risk for all-cause mortality, or premature death from any cause (42–45,45–50).

It is important to understand that the statement that carbohydrates are “nonessential” is not only factually inaccurate, it results in adopting a low-carbohydrate diet or ketogenic diet that increases your risk for a wide variety of chronic health conditions that may ultimately shorten lifespan, decrease your quality of life, and accelerate your risk for chronic disease.

People in the ketogenic community often measure their fasting insulin levels as an indicator of their glucose metabolism. A fasting insulin test measures the amount of insulin your pancreas must secrete in order to control your blood glucose.

The lower the number, the less work your pancreas is performing. This is a good thing.