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Intermittent Fasting & Hypothyroidism 2025: Is It A Good Idea?

Intermittent Fasting (IF) is an eating pattern that alternates between eating and fasting periods (not eating).
Societies around the world practice fasting for a variety of health and spiritual purposes. As more intermittent fasting studies shed light on the variety of benefits associated with the practice, the approach is becoming more popular.
But what happens when a chronic health condition like hypothyroidism enters the mix?
This question might seem daunting, given that hypothyroidism—an underactive thyroid gland—affects the body’s metabolic processes.
This article explores the intertwining threads of Intermittent Fasting and hypothyroidism. The aim is to provide those living with hypothyroidism, their loved ones, and the health-conscious among us with information about this unique approach to eating safely.
Intermittent Fasting For Hypothyroidism: Is It Safe?
Though it offers great health benefits, intermittent fasting side-effects can be quite pronounced. But it requires careful implementation, especially for those with hypothyroidism.
Medical professionals express diverse views on this subject, balancing potential benefits. Key concerns include:
- Alterations in thyroid hormone levels due to fasting, calorie restriction, and thyroid medication dosing changes.
- Potential stress on the adrenal glands, which can exacerbate symptoms in some individuals.
- The risk of exacerbating eating disorders for those predisposed to such conditions.
Intermittent Fasting And Hypothyroidism: Is It Safe?
Though it offers great health benefits, intermittent fasting side-effects can be quite pronounced. But it requires careful implementation, especially for those with hypothyroidism.
Medical professionals express diverse views on this subject, balancing potential benefits. Key concerns include:
- Alterations in thyroid hormone levels due to fasting, calorie restriction, and thyroid medication dosing changes.
- Potential stress on the adrenal glands, which can exacerbate symptoms in some individuals.
- The risk of exacerbating eating disorders for those predisposed to such conditions.
Prolonged fasting can have complex effects on hormone levels, both good and bad. In a study of Ramadan fasting–which involves a month of eating only when the sun is down–most Muslims with hypothyroidism chose to fast and were able to do so safely[1].
A minority of patients on thyroid medications had some complications they could manage with physician assistance. The issues were likely caused by the extended delay between main meals, which also affected the timing and metabolism of the medication.
So while it looks like individuals with thyroid issues can adopt intermittent fasting, they should consult a healthcare provider before initiating an IF regimen or other hypothyroidism diet.
Intermittent fasting can have side effects.
What Is Intermittent Fasting?
Intermittent Fasting (IF) is more than a fad—it’s a lifestyle many healthy people have adopted for its potential benefits.
At its core, IF is not a diet but an eating pattern. The practice involves focusing on when you eat rather than what.
Common approaches to Intermittent Fasting include:
- The 16/8 method: Eat during a set 8-hour window; fast for the other 16 hours each day. Just getting rid of late-night snacking can do wonders for your health.
- The 5:2 method: Eat normally five days a week, and restrict calories to about 500-600 on two non-consecutive days.
- Eat-Stop-Eat: This involves a 24-hour fast once or twice a week.
Fasting periods cause the body to change its hormonal balance, promoting fat loss and increasing metabolism. According to some studies, this practice can lead to weight loss[2], improved metabolic health, and even pain relief[3]. Some patients combine intermittent fasting and keto diets to enhance their results.
What Is Hypothyroidism?
Hypothyroidism, or underactive thyroid, is when the thyroid gland is not producing sufficient thyroid hormones. This shortage can have wide-ranging effects on the body, causing symptoms such as weight gain, fatigue, and sensitivity to cold.
What Causes Hypothyroidism?
Hashimotos is an autoimmune condition affecting the thyroid gland. It’s the most common cause of hypothyroidism. Other causes include:
- Iodine deficiency: Iodine is crucial for the production of thyroid hormones. A diet too low in iodine can lead to hypothyroidism.
- Thyroid surgery: If all or a large portion of the thyroid is removed, it can result in hypothyroidism.
- Radiation therapy: Radiation used to treat head and neck cancers can affect the thyroid.
- Certain medications: Some drugs used to treat other illnesses–such as psychiatric conditions, heart problems, and certain cancers–can also affect thyroid function and cause hypothyroidism.
- Pituitary disorder: Issues with the pituitary gland–such as a developmental disorder, tumor, or trauma–can interfere with thyroid hormone production.
- Congenital hypothyroidism: There are some babies with a thyroid gland that does not function properly.
- Pregnancy: Some women develop hypothyroidism associated with pregnancy. It can even hit after pregnancy (postpartum hypothyroidism) because the women produce antibodies to their own thyroid gland.
The Role Of Thyroid Stimulating Hormone (TSH)
Thyroid Stimulating Hormone, or TSH, is a hormone produced by the pituitary gland. It stimulates the thyroid to produce and release thyroid hormones into the bloodstream. TSH levels are used in the diagnosis and treatment of thyroid disorders.
How Does Fasting Affect Thyroid Function?

Intermittent helps with thyroid disease and insulin sensitivity.
Intermittent fasting (IF) can influence thyroid function by improving insulin sensitivity. This is crucial for those with hypothyroidism, who often struggle with weight gain and insulin resistance.
Insulin Resistance And Hypothyroidism
Insulin is an important hormone that influences blood sugar levels. It helps cells absorb sugar (glucose) from the bloodstream, preventing blood sugar from getting too high.
Insulin resistance is a condition where cells in your body don’t respond well to insulin. In response, your pancreas produces more insulin to compensate. Eventually, your pancreas can no longer keep up. The resulting high blood sugar levels are the hallmark of type 2 diabetes.
Research suggests[4] a higher prevalence of insulin resistance among patients with thyroid disease. This is likely due to the slowed metabolism and weight gain commonly associated with low thyroid hormones.
This relationship means that managing insulin resistance can be crucial to managing hypothyroidism.
Intermittent Fasting And Insulin Resistance
Studies show[5] that intermittent fasting can help lower body weight, fasting glucose, and insulin levels and reverse insulin resistance. It also alters hormone levels, which can reduce the need for insulin therapy when done under a doctor’s supervision.
7 Intermittent Fasting Benefits For Thyroid Patients
Intermittent fasting helps with weight loss.
Weight Management
One of the most appealing benefits of Intermittent Fasting is its potential for weight control. By regulating the eating window, individuals can better manage calorie and food intake and potentially help lose weight.
Improved Insulin Sensitivity
Intermittent fasting promotes insulin sensitivity and may be a viable non-pharmaceutical treatment option. When your cells respond better to insulin, you can achieve better blood sugar control and metabolic health.
Enhanced Energy Levels And Metabolism
While hypothyroidism can often lead to fatigue and slow metabolism, some people report[6] increased energy levels with Intermittent Fasting.
Reduction In Inflammation
Intermittent fasting may help reduce inflammation, a common feature of many autoimmune conditions, including Hashimoto’s disease. Chronic inflammation can affect thyroid function; thus, reducing inflammation could support better thyroid health.
Enhanced Cellular Repair Processes
During fasting, the body initiates cellular repair processes, such as removing cell waste. These processes can contribute to better overall health and well-being, which benefits individuals with any chronic condition.
Potential Improvement In Gut Health
Emerging evidence suggests intermittent fasting may benefit gut health by influencing the gut microbiome. Since gut health can impact the immune system and inflammation levels, this could indirectly affect thyroid health.
Improved Mental Clarity And Concentration
Some people report experiencing improved mental clarity and concentration during fasting periods. This improvement in brain function could be particularly relevant since brain fog is a common symptom in hypothyroid patients.
Remember, while these potential benefits can sound promising, people with hypothyroidism need to approach intermittent fasting with the guidance of a healthcare provider due to the potential impact on thyroid hormone levels.
How To Start Intermittent Fasting With Hypothyroidism
Every medical decision is complicated when you have a chronic condition like hypothyroidism. Some things to consider before you start intermittent fasting include:
Seek Medical Guidance
Anytime you have a chronic condition, you should talk with a healthcare provider before making major changes to your lifestyle. Your primary doctor, functional medicine specialist, or dietician can help you decide if IF is a good idea for you.
Choose The Right Fasting Method
There are various forms of IF. Your lifestyle, preference, and health condition all impact which style to adopt.
For those with hypothyroidism, a more moderate approach (such as the 16/8 method) may be more suitable. Talk to your healthcare provider about the smartest approach for you, and be open to change if it’s not working.
Listen To Your Body
Any time you change your diet, you want to track what your body tells you. Monitor your energy levels, hunger, and any symptoms of aggravated thyroid issues.
If you feel unwell or excessively tired, or if your hypothyroid symptoms worsen, it’s crucial to seek medical advice. Intermittent fasting is a tool for health improvement, but it should not cause distress or harm. Always prioritize your well-being and adjust your approach if needed.
Conclusion
Intermittent Fasting (IF) offers many benefits. It can help you maintain calorie restrictions and weight loss. It may treat subclinical hypothyroidism and autoimmune disease. You may also experience reduced inflammation and potentially enhanced cellular repair and gut health.
However, if you have hypothyroidism, it’s crucial to approach IF with caution. Changing your diet can have a potential impact on thyroid hormone levels. Always seek professional guidance before starting, choose a suitable fasting method, and listen to your body’s responses. Remember, your ultimate goal is to improve your health; each person’s journey will be unique.
+ 6 sources
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- Budour Alkaf, Siddiqui, M.K., Ali, T., Bakir, A., Murphy, K., Karim Meeran and Nader Lessan (2022). Ramadan Fasting and changes in thyroid function in hypothyroidism: identifying patients at risk. [online] doi:https://doi.org/10.1089/thy.2021.0512.
- Izzah Vasim, Chaudry Nasir Majeed and DeBoer, M.D. (2022). Intermittent Fasting and Metabolic Health. [online] 14(3), pp.631–631. doi:https://doi.org/10.3390/nu14030631.
- Caron, J., Kreher, M., Mickle, A.M., Wu, S., Przkora, R., Estores, I.M. and Sibille, K.T. (2022). Intermittent Fasting: Potential Utility in the Treatment of Chronic Pain across the Clinical Spectrum. [online] 14(12), pp.2536–2536. doi:https://doi.org/10.3390/nu14122536.
- Gierach, M., Gierach, J. and Junik, R. (2014). Insulinooporność a choroby tarczycy. [online] 65(1), pp.70–76. doi:https://doi.org/10.5603/ep.2014.0010.
- Aljadah, M. and Bakke, J. (2021). Intermittent fasting: is there a role in the treatment of diabetes? A review of the literature and guide for primary care physicians. [online] 7(1). doi:https://doi.org/10.1186/s40842-020-00116-1.
- Izzah Vasim, Chaudry Nasir Majeed and DeBoer, M.D. (2022). Intermittent Fasting and Metabolic Health. [online] 14(3), pp.631–631. doi:https://doi.org/10.3390/nu14030631.