In 2017, one of the most highly-searched terms was “ketogenic diet.” Today, I want to dive a bit deeper into what the ketogenic diet is, the relationship between hypothyroidism and keto diet and keto and thyroid medication.

I will also uncover what the ketogenic diet may or may not help. Is the ketogenic diet good for hypothyroidism? Let’s find out today.

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The Ketogenic Diet Defined

In a state of ketosis, your body burns up fat faster than you can supply it.

Sounds simple enough, right? In fact, it’s easy to see how this method would result in shedding pounds like they were not even there (Read: Keto Curious, understanding the science behind ketogenic diets).

It stems from a simple process, but one that sounds too good to be true (and we will dive into whether or not it is later on).

Eating “ketogenic foods,” and following a ketogenic diet, will have you:

  • Losing Weight
  • Feeling Healthy
  • Having Better Brain Function

Key Insight: There’s an important distinction to be made between the ketogenic diet and metabolic ketosis. Any diet that supplies less fuel than needed will cause the body to form ketones. This can occur regardless of the levels of carbohydrate and fat intake in the diet.

The Big Difference

Here is the big difference. When in a state of metabolic ketosis, any time that you are not getting enough fuel, your body will convert fats into fuel (and will eventually use your own fats, if you run out of glycogen). That process does result in some ketones being made.

If you were to have Hashimoto’s disease, or hypothyroidism due to another cause, is this sort of diet a good idea for you? The most thorough amount of research that has been done on this diet has centered around children with epilepsy.

I will mention more as we go along, but it is important to note that this audience is the main source of data that we have on possible thyroid side effects.

Bottom Line: All studies on the keto diet and thyroid, done to date, agree that the ketogenic diet has the potential to be harmful to thyroid function. The findings here are especially important because thyroid disease increased with age (and is less common in pediatric populations).

The Ketogenic Diet and Thyroid Disease

When it comes to the more recent and higher-quality studies performed, they are ones which looked at kids who were on the ketogenic diet for the prevention of seizures.

The First Study

In the largest study, 120 children (of both genders), between the ages of 4 – 11, were treated with the diet for at least 1 year. After 1, 3, 6, and 12 months on the diet, the following were measured:

  • Free T3
  • Free T4
  • Thyroid-stimulating Hormone (TSH)

The rate of hypothyroidism among preadolescent children is roughly 1 in 1250, or about 0.08%.1 As part of this study, 1 in 6 of the children became hypothyroid and required thyroid replacement therapy.

Key Insight: As per one of the largest studies on the ketogenic diet, the rate of hypothyroidism among children was 20,800% higher than would be expected from simple, random chance.

Due to these findings, the researchers concluded that the diet itself caused thyroid malfunction. Ultimately, they suggested that thyroid function should be monitored regularly in those with epilepsy who were on the ketogenic diet.2

The Second Study

In the second study, researchers tracked children for two full years. They found that thyroid function did change, and that the change was more pronounced in those who:

  • Were on the diet for longer
  • Had blood levels of cholesterol and triglycerides
  • Encountered seizures earlier in life

These researchers came to the same conclusions as the first, that if a patient was to be on this particular diet, their thyroid function would need to be monitored closely.3

Why Does The Ketogenic Diet Slow Thyroid Function?

One of the benefits of the ketogenic diet is that it may lower insulin levels. Many people can have problems when it comes to having too much insulin.  Yet, too little can also be just as bad.

Insulin appears to be important for several facets of thyroid function, including the liver’s ability to make the more potent thyroid hormone T3 out of T4.4

Bottom Line: If you are on a diet that lowers your insulin levels to the point where your liver cannot adequately make T3 out of T4, you are inadvertently doing damage to your thyroid.  This is done by pushing your levels way too low.

What About Adults?

The studies that we cited earlier focused primarily on children, and even though I had mentioned that thyroid problems do get worse with age, it is important to consider some of the research done on adult populations.

In fact, the earliest studies on the ketogenic diet and thyroid function were on adults. They evaluated how very low carb diets, that were not low in calories, affected thyroid hormone levels in adults.

Understanding The Findings

The findings were such that the lower the diet was in carbs, the more T3 lowered and reverse T3 elevated. This was also the same change noted in cases of starvation, as the body attempted to slow its metabolic rate (in order to store fat and stave off illness and death).

This study found that it was not just starvation, but that carbohydrate restriction itself was responsible for the changes in thyroid function.5

Another study performed, on completely healthy volunteers, showed the exact same findings. On a ketogenic diet, the thyroid function slowed. T3 levels dropped, and reverse T3 elevated. This change occurred even when the calories were not reduced.6

Bottom Line: The ketogenic diet has been shown to slow thyroid function in both children and adults. No doubt about it.

What does slow thyroid function mean for you? It can result in numerous symptoms, such as:

  • Easy weight gain
  • Hair loss
  • Depression
  • Fatigue
  • Higher risk for chronic disease
  • Many other complications

What Else Do We Know About the Ketogenic Diet?

It became clear to me, after digging into the science behind this popular diet, that the excitement behind it was buoyed more on speculation than evidence. Besides thyroid function, there were also other areas studied – the most included were on:

  • Epilepsy
  • Athletic performance
  • Weight loss
  • Cancer


Evidence has shown that the ketogenic diet can be helpful for pediatric epilepsy which has been otherwise non-responsive to medication. This is by far the best-studied application of the diet, but it is not a magic bullet by any means (it may not even work for 78 – 85.5% of patients).7

There are also inherent risks when it comes to treating epilepsy this way, so much so that there are debates whether or not the benefits of fewer seizures are even worth it.8 The risks include:

  • Early Adverse Effects – such as gastrointestinal distress, acidosis, hypoglycemia, dehydration, and lethargy.
  • Late Adverse Effects – such as hyperuricemia, hyperlipidaemia, kidney stones, easy bruising, and decreases in height and weight.

Bottom Line: The positive effects that we know about the ketogenic diet revolve around young patients and epilepsy. But it is certainly not a cure all in these terms. It can help some, with risk, but for most it simply does not work (the vast majority, even).

Athletic Performance

How does the ketogenic diet contribute to athletic performance? A high-fat, low-carb diet may impair exercise performance by reducing the capacity to utilize carbs effectively.  This would typically go on to be a key fuel source of skeletal muscles during intense, endurance-based exercise. So, what does this mean?

Recently, we have seen an influx of ketone body supplements (like ketone salts and esters) on the market These can be used to rapidly increase ketone body availability (without the need to first adapt to a ketogenic diet).

However, the extent to which ketone bodies regulate skeletal muscles and metabolism during prolonged periods of exercise remains unknown.

Therefore, as of this moment, there is no reliable information to suggest that it would improve your athletic performance.9 (Read:  How can you boost your metabolism)

Bottom Line: While, in some studies, athletes might have felt their energy levels drop at first, but a stronger “second wind” carrying them through, the general ability to maintain high levels of endurance-based exercise was lowered.10

Weight Loss

The most attractive aspect of the ketogenic diet is often that it does not matter how much food you are consuming, as long as you are still within a ketogenic state.

Can you use the ketogenic diet to lose weight? A controlled isocaloric study showed that the proportion of carbs to fats in the diet is irrelevant to energy expenditure and weight loss. Particularly when dietary proteins and energy intake are held at a constant.11

The big promise of the ketogenic diet only leads to weight loss if there is a fuel deficit. There is no chain reaction, and no inspiration for your body to start burning up fat out of control (Read: Carbs vs ketosis).

If you want to be below a threshold of having less hunger, that’s reasonable. The key to doing that is all about eating a good variety of:

  • Quality protein
  • Lots of plant foods
  • Lots of fiber-rich foods

Bottom Line: The ketogenic diet may result in a decrease of weight and body fat, but it is certainly not the magic bullet that some may claim for weight loss or proper dieting. It requires more nuance, and a greater emphasis on “metabolic ketosis” in the body.

Cancer Growth

This is an especially important topic to consider. There were some speculative studies in the past which thought that the diet may be helpful. But, the newest studies suggest quite the opposite. In fact, for most types of cancer, it is harmful.

Key Insight: This is something I think that you really need to know about speculative data. While it might be good enough to avoid risk, it is not good enough to base action upon. If the evidence simply is not there, or if it is shaky, you are best off avoiding it.

What we have found about ketones is that they may stimulate breast cancer in some,12 and that by blocking ketone formation we may be able to do a better job of stopping cancer growth.13

This all comes down to the fact that ketones and lactate can increase cancer cell “stemness”.  This can drive recurrence, metastasis, and poor clinical outcomes in breast cancer.14

Bottom Line: No matter what you might have heard, recent studies are showing that ketones may play a role in the development of cancers (like breast cancer). If you had heard that ketogenic diets beat chemotherapy for almost all cancers, there is little clinically to suggest that this is at all true.

Ketogenic Speculations

There are both good and bad speculations when it comes down to the ketogenic diet.  Unpacking the science a bit has hopefully helped us understand that the bad may weigh out the good when it comes to this diet.

For the good, the ketogenic can help with:

  • Those with diabetes complications, and
  • Neurodegenerative diseases

On the other hand, the ketogenic diet can have a negative effect on:

  • Diabetes (which is a bit of a paradox)
  • Neurodegenerative diseases
  • Cortisol metabolism
  • Immune health
  • Gut flora
  • Detoxification
  • Hormone regulation
  • Brain cell repair

Bottom Line: If something is billed as a magic bullet, or the cure to all of life’s problems, sometimes you need to dig a bit deeper into the research. When it comes to the ketogenic diet, we might be seeing more flash than substance.

The Ketogenic Diet & Thyroid Health

Is the ketogenic diet safe? The research on the thyroid and keto diet would suggest that it is not. While it might seem like a miracle cure, the research suggests the opposite.

We spent a little bit of time delving into some of the more recent data, I fully intend on keeping you up to date as more comes out.

After all of that, isn’t it time that you learned a little bit more about your thyroid? It’s as simple as taking a quick quiz. This is where easy questions can unlock a world of answers about your thyroid health (and how you feel in general).

Please give the Thyroid Quiz a look today (Click Here), and set yourself on the right track towards your best health.


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P.S. Whenever you are ready, here is how I can help you now: 1. Schedule a Thyroid Second Opinion with me, Dr. C, Click Here for Details 2. Download and use my Favorite Recipes Cookbook Here 3. Check out my podcast Medical Myths, Legends, and Fairytales Here Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist and the author of The NY Times bestselling Adrenal Reset Diet, The Metabolism Reset Diet and The Thyroid Reset Diet. Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, diabetes, and regain energy. Learn more about the surprising story that started his quest.