Intermittent fasting has become a popular diet and health trend in recent years. It involves alternating between periods of fasting and eating. Many people use intermittent fasting for weight loss and other health benefits like lowering blood sugar and improving cardiovascular health. But is intermittent fasting a good option for people with thyroid disorders like hypothyroidism or Hashimoto’s thyroiditis? In this comprehensive article, we will examine the research on whether intermittent fasting is beneficial or harmful for thyroid function and thyroid hormone levels.
What is intermittent fasting?
Intermittent fasting simply means going for extended periods without eating, followed by periods of eating. This contrasts with the normal pattern of eating frequently throughout the day. There are several different types of intermittent fasting schedules:
- 16/8 method: Fast for 16 hours per day, eat only during an 8 hour window.
- Eat-Stop-Eat: Fast completely 1-2 days per week.
- 5:2 diet: Eat very few calories 2 days per week, eat normally other days.
- Alternate day fasting: Eat very little every other day.
The most common type of intermittent fasting is the 16/8 method. This involves skipping breakfast and restricting eating to an 8 hour window, like 12pm to 8pm. Some people extend the fasting window further to 20 or 22 hours. The key is that fasting periods are alternated with periods of normal eating.
Benefits of intermittent fasting
Intermittent fasting has been shown in research to provide the following benefits:
- Weight and body fat loss: By restricting calories and meal frequency, intermittent fasting can help burn fat and reduce body weight.
- Lower inflammation: Fasting reduces inflammatory markers like cytokines.
- Increased insulin sensitivity: Fasting can improve how your body processes sugars and uses insulin.
- Boosted metabolism: Short term fasting may increase resting metabolism.
- Longer lifespan: Animal studies show fasting supports longevity.
- Brain health: Fasting may aid neuron growth and protect brain function.
These benefits have made intermittent fasting an appealing diet tool for weight management and health improvement. Proponents claim it is a more natural and effective approach than chronic calorie restriction for fat loss.
How does intermittent fasting affect thyroid function?
Now that we have covered the basics of intermittent fasting, let’s examine how it may impact thyroid health specifically.
The thyroid gland produces thyroid hormones T4 and T3 which regulate metabolism. Hypothyroidism is when the thyroid does not make enough hormones, causing fatigue, weight gain and other signs. Hashimoto’s is an autoimmune disorder that damages the thyroid.
Here are several ways fasting could potentially influence thyroid function:
- Lower T3 levels: Fasting triggers a drop in circulating T3 hormones. T3 is the more metabolically active hormone.
- Higher rT3: During fasting the inactive reverse T3 (rT3) rises as T3 drops.
- Lower TSH: Intermittent fasting can reduce thyroid stimulating hormone (TSH).
- Inflammation reduction: Fast periods lower inflammation which may help autoimmune thyroiditis.
- Circadian disruption – Intermittent fasting could potentially disrupt normal hormonal circadian rhythms long term.
In summary, fasting impacts thyroid hormone kinetics and TSH levels over the short term. But whether these temporary fluctuations are beneficial or detrimental is not fully clear.
Does intermittent fasting help or hurt thyroid function?
Let’s review the evidence on how intermittent fasting and different fasting protocols may help or impair thyroid health:
Potential benefits of intermittent fasting for thyroid
- Lowered thyroid antibody levels – A small study in obese women with Hashimoto’s found 16/8 intermittent fasting for 12 weeks reduced anti-TPO and anti-TG antibodies compared to a regular diet. This indicates fasting lowered autoimmune activity against the thyroid.
- Reduced inflammatory cytokines – Inflammation impairs thyroid function in autoimmune thyroiditis. Fasting reduces inflammatory mediators like IL-6 and may benefit autoimmune thyroid patients.
- Increased human growth hormone – Fasting raises growth hormone. In one study, a 3 day fast increased growth hormone by over 1300%. Growth hormone helps convert T4 to T3.
- Cellular autophagy – Periods of fasting induce autophagy, where cells digest and remove waste material. This housekeeping process may benefit thyroid cell health.
Based on the evidence, potential upsides of intermittent fasting for the thyroid are reduced inflammation and thyroid autoimmunity, increased growth hormone, and triggered autophagy.
Potential downsides of intermittent fasting for thyroid
- Lower T3 levels – Fasting consistently lowers T3 thyroid hormone levels which may slow metabolism.
- Increased rT3 – Studies show a rise in inactive rT3 thyroid hormone during fasting. High rT3 is linked to hypothyroid symptoms.
- Lower TSH – Intermittent fasting can lower TSH. Very low TSH can possibly indicate pituitary dysfunction.
- Circadian disruption – Erratic meal timing and caloric restriction may disrupt circadian rhythms critical for optimal hormonal function.
- Hunger and cravings – Fasting periods may increase hunger hormones like ghrelin. This can lead to overeating when not fasting.
Potential drawbacks of intermittent fasting for thyroid health include declining active thyroid hormones, rising inactive rT3, disrupted circadian signals, and increased hunger and cravings.
Intermittent fasting protocol considerations for thyroid patients
Since intermittent fasting has mixed effects on thyroid function, people with hypothyroidism or Hashimoto’s may need to take some precautions and modify how they practice intermittent fasting.
Here are some tips for making intermittent fasting work better with thyroid disorders:
- Avoid very long fasts – Stick to overnight fasts up to 16-18 hours. Extended 24+ hour fasts can severely drop thyroid hormone levels.
- Eat thyroid supporting foods – Make sure to eat nutritious whole foods like seafood, Brazil nuts, berries and vegetables during eating periods.
- Supplement if needed – People with hypothyroidism may need small amounts of T3 thyroid hormone or iodine supplements while fasting.
- Monitor symptoms – Pay attention to symptoms like fatigue, coldness, constipation and weight changes which could indicate fasting is lowering metabolism.
- Measure thyroid levels – Get TSH, free T4 and free T3 levels tested to ensure thyroid levels don’t drop too low with fasting.
- Be gradual – Start with 12-14 hours fasting and gradually increase towards 16-18 hours. Sudden drastic fasting can be stressful.
- Listen to your body – Don’t force longer fasts if feeling unwell. Shorten fasting periods or frequency if not tolerating it.
People with hypothyroidism or Hashimoto’s may be able to practice gentle forms of intermittent fasting safely if they follow these tips and work with their healthcare provider. Monitor thyroid function and how you feel closely.
Should you try intermittent fasting for thyroid?
Intermittent fasting may be worth cautiously trying for some thyroid patients who wish to lose weight or reduce inflammation. But certain individuals should avoid intermittent fasting protocols:
- People with adrenal insufficiency or cortisol dysregulation may not handle fasting periods well. It can be perceived as physiological stress.
- Those with significant hormonal imbalances like estrogen dominance may not thrive with fasting’s impact on hormones.
- Women trying to conceive or who are pregnant have higher nutritional needs and should not undergo fasting.
- People who struggle with eating disorders or disordered eating may find fasting mentally disruptive.
- Diabetics on medication need to be very careful with fasting blood sugars dropping too low.
Have a discussion with your healthcare provider about whether intermittent fasting is appropriate for your individual health status and thyroid disorder. While some may benefit, others are better off avoiding fasting protocols.
Conclusions
To summarize key points on intermittent fasting for thyroid health:
- Intermittent fasting causes short term fluctuations in thyroid hormones like declining T3 and rising rT3.
- Potential benefits are reduced inflammation and autoimmunity, autophagy, growth hormone boost. But lowered thyroid hormones may also slow metabolism.
- People with hypothyroidism or Hashimoto’s can try gentle fasting but should monitor thyroid levels and symptoms closely.
- Avoid fasting if you have significant hormonal imbalances, adrenal dysfunction, or are pregnant.
- Intermittent fasting may help some thyroid patients but listen to your body and don’t overdo fasting periods.
The effects of intermittent fasting on thyroid function are complex. While some people may experience anti-inflammatory benefits, others may not tolerate the drop in thyroid hormones well. Customizing the fasting regimen and carefully monitoring its impacts is key for thyroid patients interested in exploring intermittent fasting.