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Is Water Fasting Safe For Hypothyroidism?

We often use a variety of different fasting methods to keep their weight in check. However, certain fasting practices may not be safe
Is Water Fasting Safe For Hypothyroidism?
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Fasting is the oldest and most "natural" form of dieting for humans. Indeed, our hunter-gatherer ancestors had periods when food was more abundant and times when it was scarce. Modern humans today use a variety of different fasting methods to keep their weight in check. However, certain fasting practices may not be safe for people with specific health conditions. Here, we discuss water fasting and explore if it is safe for people with hypothyroidism.


What is water fasting?

Water fasting is when a person does not consume anything aside from water for a length of time. Technically, most people who practice various forms of intermittent fasting do a water fast, as they restrict food for several hours overnight. But, water fasts usually last at least a day or two and may even extend up to 72 hours.

People primarily use water fasts to lose weight. However, they may also water fast for spiritual reasons, before surgery, and for other health benefits like detoxing their system. 


How do you do water fasting?

There are no scientific guidelines behind water fasting, and you can tailor this fasting to your specific needs. However, people generally do a water fast between 24 and 72 hours. 

Before you do your first water fast, it can help to decrease meal portions to allow your body time to adjust to a decrease in food intake. Alternatively, you can also try intermittent fasting, where you fast for fewer hours at a time.

Some people should seek medical advice before water fasting, especially those with diabetes, eating disorders, women who are pregnant, older adults, and people with heart issues. 


What are the potential benefits?

The human digestive system was not designed to work constantly. Yet, because of ease of access to food, food abundance, and the different nutritional composition of the modern-day diet, people tend to eat around the clock. Because most people eat first thing in the morning and right up until bedtime, the digestive system is continually working to break down food - even in our sleep. Therefore, one of the first things water fasting can do is give the digestive tract a break. 

But, aside from a much-needed rest, water fasting may also do other things for the body, including:

  • Improving regulation of the circadian rhythm
  • Restoring balance in the gut microbiome
  • Preventing weight gain
  • Warding off metabolic dysfunction
  • Enhancing kidney and cardiovascular function by lowering blood pressure
  • Promoting autophagy (a process where old cells break down and get recycled)

Most people use fasting to help with weight loss. Water fasting may help people lose weight because it allows the body to use alternative energy sources aside from glucose, such as ketone-like sources. Therefore, it may be a valuable tool for stabilizing blood sugar levels in people with metabolic dysfunction.

Water fasting may also boost your sensitivity to the hormones leptin and insulin. Leptin helps you feel full, whereas insulin pulls glucose from your bloodstream into your cells.

Is water fasting safe for the thyroid?

Some research suggests water fasting affects thyroid function. The thyroid gland is the metabolic powerhouse of the body, meaning that it regulates how cells utilize energy. To do this, the thyroid releases thyroid hormones that tell all the cells in the body what to do.

There are two primary states of thyroid disease: hypothyroidism and hyperthyroidism. Hypothyroidism is the most common, where thyroid hormone levels are too low, causing body systems to slow down. An autoimmune condition called Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States. Hyperthyroidism is where thyroid hormone levels are too high, causing body processes to speed up. 

Most studies show that short-term intermittent fasting does not significantly impact thyroid hormone levels. However, it may enhance the absorption of thyroid medications like levothyroxine, depending on when it is taken. Additionally, if you have Hashimoto's disease, well-timed fasting may improve inflammation and decrease the severity of autoimmune symptoms. 

Because every person is unique, with individual responses to dietary changes, it is vital to work with a doctor—especially if you have a chronic health condition like hypothyroidism. Fasting can benefit specific individuals, but it can also have health consequences, especially for those with other chronic health conditions like type 2 diabetes. 

Additionally, getting regular thyroid function tests is imperative if you are using dietary measures to help treat your thyroid.

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How to navigate diet and your thyroid

Millions of Americans attempt to diet yearly for weight control and to improve their overall health. However, very few people find success in dieting. Yet, we know that certain nutritional principles are vital to bettering your overall health and well-being, including:

  • Avoiding processed foods and added sugars
  • Increasing your intake of whole, nutrient-dense foods that contain protein, healthy fats, and plenty of vitamins and minerals
  • Limiting snacking between meals so your body has a chance to burn and store energy effectively
  • Eating a protein-rich breakfast every day
  • Giving yourself a natural overnight fast by cutting out late-night snacking to curb your risk for abdominal obesity and diabetes

Before trying water fasting with an underactive thyroid gland, meet with your thyroid care team to see if it is a safe option for you.


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Julia Walker, RN, BSN

Clinical Nurse

Julia Walker, RN, BSN, is a clinical nurse specializing in helping patients with thyroid disorders. She holds a Bachelor of Science in Nursing from Regis University in Denver and a Bachelor of Arts in the History of Medicine from the University of Colorado-Boulder. She believes managing chronic illnesses requires a balance of medical interventions and lifestyle adjustments. Her background includes caring for patients in women’s health, critical care, pediatrics, allergy, and immunology.

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