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Ketogenic Diet and Hypothyroidism

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One of the hottest diet fads of today is the Ketogenic diet, which is characterized by low carbohydrate and high fat content. Popular amongst healthy and overweight adults alike, this diet has been credited for massive amounts of weight loss.

Despite its effectiveness, caution should be observed in some people, especially those with thyroid problems. If you are thinking of trying this fad diet, do some research first and read the important points below:

What is the Ketogenic Diet, Anyway?

As it has been mentioned, the Ketogenic diet features meals which are low in carbohydrate and high in fat. It operates through the severe restriction of carbohydrate intake, while fat intake is increased to balance the energy deficit. As a result, lipid oxidation takes place, and ketones are produced. Nutritional ketosis is achieved as ketones serve as the primary energy source, instead of the usual glucose.

History of the Ketogenic Diet

The Ketogenic diet was developed to treat epilepsy in the 1920’s, and later on was also prescribed in individuals suffering from neurodegenerative conditions. However, the beginnings of the Ketogenic diet – fasting – can be traced back to the ancient times, with fasting being credited in the Hippocratic collection as the only effective measure against epilepsy.

It was in 1911 when fasting’s promise was rediscovered by French physicians Gulep and Marie, who noted that starvation lessened the seizure episodes of 20 epileptic patients. More than a decade later, American doctor H. Rawle Geyelin presented the cognitive improvements that occur after fasting in a National Convention. At the same time, Harvard’s Stanley Cobb and W.G. Lennox worked on starvation as treatment for epilepsy; both noted a decrease in seizures 2-3 days after the start of the program. The duo credited the positive effect to the change in metabolism which stemmed from the body’s effort to burn fats for energy.

From these studies, Dr. Wilder of the Mayo Clinic came up with the idea of producing ketonemia as an alternative for fasting. This became the basis of the Ketogenic diet as treatment for epilepsy. Experts believed that the said diet could be better tolerated compared to taxing process that is fasting.

It was another staff of the Mayo Clinic, Peterman, who came up with the calculation of the Ketogenic diet – the same one that is used until today: 1 gram of protein per kilogram of body weight (in children,) 10-15 grams of carbohydrates per day, with the remaining calories to be delivered via fat sources. As expected, Peterman’s calculations for the Ketogenic diet yielded impressive results – cognition and behavior of the affected children vastly improved following the diet regimen.

For decades, many physicians followed the Ketogenic diet protocol – but when anti-epileptic drugs such as diphenylhydantoin was developed in 1938, sights were shifted to the promise of pharmacological cure. The Ketogenic practice was thrown to the wayside until NBC’s Dateline aired the story of 2-year-old Charlie, a Chinese boy with intractable seizures. He was subsequently treated with Ketogenic diet at the Johns Hopkins Hospital. Ever since then, the regimen – used either as treatment for epilepsy or as a means for weight loss – has become more popular than ever.

Benefits of the Ketogenic Diet

Although it mimics the state of starvation, the Ketogenic diet actually reaps a lot of benefits, and they include:

  • Greater Weight Loss

Although caloric intake is increased with the Ketogenic diet, it yields better weight loss in a study of overweight adolescents. Additionally, a study of obese adults has shown that a 6-month Ketogenic diet regimen can lead to as much as 32 pounds in weight loss.

Experts suggest that this might be due to the maintenance of the metabolic rate, which occurs following high caloric intake. It can also be attributed to better satiation and reduced hunger due to the increase in fat consumption. Lastly, beta-hydroxybutyrate, a ketone that circulates in the body, is said to exert an inhibitory effect on the appetite. Given the following factors, the Ketogenic diet is said to result in dramatic reductions in total body mass and abdominal circumference.

  • Positive Effects on Cardiovascular Health

Many experts were initially apprehensive of the Ketogenic diet because it promotes a high-fat diet, which is in stark contrast with the usual recommendation that is the high carbohydrate, low fat diet. Although this is the case, many studies have shown that the Ketogenic diet is actually beneficial to heart health.

In fact, 23 trials have proven that the Ketogenic diet is effective in reducing systolic and diastolic blood pressures, plasma triglycerides, and C-reactive protein. It was also deemed helpful in increasing the levels of high-density lipoprotein cholesterol, otherwise known as the ‘good cholesterol.’

  • Better Glucose and Metabolic Management

Apart from enhancing heart health, the Ketogenic diet has been deemed beneficial for diabetics as well. Studies show that the said diet can lead to lower fasting plasma glucose, glycated hemoglobin, and plasma insulin levels.

The Ketogenic diet has also been deemed effective in reversing the effects of Polycystic Ovary Syndrome, which is one of the most common metabolic disorders in women.

  • Enhancement of Sleep Patterns

More than just facilitating weight loss and better health, the Ketogenic diet also seems to be the solution for people with sleeping difficulties. A study of narcoleptic people has shown that the participants experienced improvements in daytime sleepiness following the Ketogenic diet. However, some studies suggest that the enhancements in sleep – specifically the increases in rapid-eye movement sleep – can be attributed to the weight loss that comes with the Ketogenic diet.

Effects on Thyroid Health

The Ketogenic diet affects many body systems, including that of the thyroid gland. Studies show that a low carbohydrate, high fat diet can lead to the following thyroid alterations:

Decrease in Serum T3 and Increase in Serum rT3

The study of Mathieson et al features 12 obese women who were grouped according to a high-carbohydrate, very low calorie, and low calorie diets. Weekly measurements of thyroid function showed serum T3 decreases in the low calorie and very low calorie diet groups, with changes occurring faster in the former. Serum rT3, on the other hand, increased following the very low calorie diet.

The same decrease in serum T3 was seen in the study of Ullrich et al, specifically in participants who undertook high fat, low carbohydrate diets.

Explanation: During the state of fasting (as experienced with the Ketogenic diet,) T3 levels decrease. The opposite is the case for reverse T3, as its levels usually increase following starvation. The said results denote the “sick euthyroid syndrome,” where thyroid hormones are unusually low in individuals with nonthyroidal systemic illness. For confirmatory purposes, a TSH test is prescribed to confirm if hypothyroidism is developing if not.

Increase in Thyroid-Stimulating Hormone (TSH) Levels

A study made by Koze et al featured 120 patients who were treated with the Ketogenic diet for a year. Their findings showed baseline elevation of TSH.

Explanation: TSH works by stimulating thyroid growth and the consequent production of thyroid hormones. While Low T3 and elevated rT3 denote the sick euthyroid syndrome, an increase in TSH levels confirms the diagnosis of hypothyroidism.

Such a finding was posited in the study above, as participants were diagnosed with hypothyroidism at 1, 3, and 6 months of Ketogenic diet therapy. The deviations were significant enough for the physicians to prescribe them with L-thyroxine.

Although some individuals develop hypothyroidism following the Ketogenic diet, some do not. Dr. Jerome Hershman, in his article for the MSD manual, asserts that “patients who have low levels of thyroid hormones but are clinically euthyroid need not take thyroid supplementation.” As such, this emphasizes the importance of thyroid function testing, especially if you plan on pursuing the Ketogenic diet for a prolonged period of time.

Increase in Total Thyroxine and Free T4 Index

The study of Volex et al has shown that men who undertook the 8% carbohydrate diet showed an 11% increase in total thyroxine and a 13% increase in free T4 index.

Explanation: Total thyroxine presents a clear picture of the clinical thyroid status in the state of non-thyroidal illness or the absence of protein-binding disorders. It is increased in hyperthyroidism; however, this comes with a decrease in TSH. For hypothyroidism, total thyroxine is decreased while TSH is increased. Similarly, an increase in Free T4 implicates hyperthyroidism, while a decrease in so connotes hypothyroidism.

Obviously, this finding is in stark difference with other studies, as most show that the Ketogenic diet can produce a hypothyroid-like state. Because of the limited number of studies linking the Ketogenic diet with hyperthyroid changes, it seems that more research is needed to determine if the said diet is safe for people with thyroid problems.

The Verdict

While the Ketogenic diet, without a doubt, works wonders for weight loss and epilepsy, it should be observed with care in people with thyroid dysfunctions.

For one, thyroid hormone production is dependent on glucose, which is dramatically reduced in a low-carbohydrate Ketogenic diet. Without enough glucose sources, hormone production and conversion are halted. This is disastrous to people with hypothyroidism, as they already have low levels of important thyroid hormones.

Apart from slowing thyroid hormone production, cutting glucose sources can lead to the synthesis of reverse T3 – which was seen in the study of Mathieson. Reverse T3 is created when the inactive T4 is not converted as properly as it should be. As the opposite of T3, reverse T3 leads to fat storage, weight gain, sleepiness, sluggishness, and insulin usage problems. In other words, it leads to the hypothyroidism symptoms that were just mentioned.

Additionally, a state of Ketosis can strain the adrenal glands, which can lead to an increased secretion of cortisol hormone. With more cortisol, thyroid function can be further decreased, which is alarming if you are already in a state of low thyroid function (hypothyroidism.)

Points to Remember

As with any other diet, the Ketogenic diet comes with some adverse effects. First timers usually report suffering from the “Keto flu,” or extreme tiredness, since a big drop in blood sugar levels usually leads to a feeling of lethargy. You need not fret though, as this feeling passes in 24 to 48 hours. Other side effects of the Ketogenic diet include bloating, constipation, and frequent urination.

Because intake of food choices is limited, the Ketogenic diet can put you at risk of micronutrient deficiencies. While helpful for Type 2 diabetics, this should NOT be tried by Type 1 Diabetics as it can lead to the development of Diabetic Ketoacidosis. This life-threatening condition, if left untreated, can lead to brain swelling, comatose, and eventual death.

Since the Ketogenic diet brings about a number of changes in the body, proceed with caution –with the guidance of a physician or nutritionist, of course. For example, naturopath Dr. David Jockers recommends following a cyclic Ketogenic diet instead of a purely strict one. This means a low-carbohydrate meal plan is followed with periods of increased carb intake in order to replenish the glycogen stores in the body. A sample program includes 6 days of Ketogenic diet, with 1 day devoted for a higher-than-usual carbohydrate intake.


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Hershman, J. M. (2018). Euthyroid Sick Syndrome – Endocrine and Metabolic Disorders – MSD Manual Professional Edition. Retrieved July 12, 2018, from https://www.msdmanuals.com/professional/endocrine-and-metabolic-disorders/thyroid-disorders/euthyroid-sick-syndrome

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