Is Intermittent Fasting Bad for People with Thyroid Issues?


hands holding empty plateIs intermittent fasting a good suggestion for individuals with thyroid points?

It’s a standard query. In any case, we all know that the thyroid gland is a delicate barometer of total caloric sufficiency within the physique. If a quick sends a message of caloric insufficiency, and the physique thinks “occasions are powerful,” the thyroid could presumably down-regulate its perform to decelerate the metabolic fee and protect power and vitamins. Warning is justifiable.

What Occurs to Thyroid Operate When You Quick?

It’s all going to be particular to the person fasting, in fact, however right here’s what research of people have proven:

In 1978, researchers positioned 45 overweight human topics on a 4-day quick, finding out their thyroid hormones ranges earlier than and through the quick, and after refeeding. Everybody’s TSH (thyroid stimulating hormone) and T4 (inactive thyroid hormone) went up through the quick. Everybody’s T3 (lively thyroid hormone) dropped. Males noticed greater modifications than girls. Once they supplemented T4 through the quick, T3 nonetheless dropped. Once they supplemented T3, T3 was maintained.

  • After the quick, what the individuals ate affected whether or not their thyroid hormones recovered.
  • Those that ate pure carbohydrate noticed their T3 return to regular.
  • Those that ate blended meals of fats, carbs, and protein noticed their T3 return to regular.
  • Those that ate solely protein nonetheless had decrease T3.
  • Those that ate solely fats nonetheless had decrease T3.

Abstract: A four-day quick depresses thyroid perform in overweight individuals with out preexisting thyroid points. Refeeding with carbs and/or a blended meal restores it; protein or fats alone doesn’t.

In 1980, researchers positioned overweight human topics with regular thyroid perform on a 10-day quick. Previous to fasting, they ate 1500 energy per day for 5 days. In the course of the quick, their T3 ranges dropped from 167 ng/dl to 86 ng/dl regardless of repeated infusions of thyrotropin releasing hormone (TRH), to which they have been unresponsive. Usually, TRH will trigger TSH to rise, thereby stimulating thyroid hormone manufacturing, however this didn’t occur through the quick.

After fasting, 5 days of 1500-calorie refeeding nonetheless weren’t sufficient for T3 and TSH responsiveness to TRH infusions to completely get well.

Abstract: A 10-day quick depresses T3 ranges and thyroid responsiveness to thyrotropin releasing hormone, even after 5 days of refeeding.

What about shorter, much less excessive fasting? Most individuals studying this aren’t doing 4- or 10-day fasts. They’re doing truncated consuming home windows. They’re skipping meals for a day, right here and there. Do we now have any research on thyroid perform throughout these sorts of fasts?

In Ramadan fasting, you eat earlier than dawn and quick till sundown. In the course of the quick, you abstain from each food and drinks (even water). Ramadan fasting is much less excessive than four-day or 10-day all-out fasts and thus a bit extra related to the common IFer.

In healthy Muslim males, Ramadan fasting has no impact on thyroid perform or hormone ranges. Aside from minor fluctuations, TSH, T3, T4, and all different measures of thyroid perform stay just about unchanged in males throughout Ramadan.

Ladies may experience drops in T4 and T3 throughout the previous few days of Ramadan.

Most apparently, Ramadan fasters who are hypothyroid sufferers taking thyroid hormones usually should not have to extend their dosages throughout Ramadan. In actual fact, they see improved high quality of life following the month of fasting.

How About Alternate-Day Fasting?

In a single study, teams of individuals with subclinical hypothyroid and regular thyroid standing have been both positioned on alternate-day fasting (25% of energy on fasting days, 125% of energy on non-fasting days) or calorie restriction (75% of energy in perpetuity) for six months. Each teams misplaced about the identical quantity of weight and physique fats. In hypothyroid sufferers, fasting produced larger enhancements in fasting insulin and insulin resistance.

In different phrases, it labored about in addition to (and in some respects, higher than) calorie restriction.

That’s about it for revealed analysis on the results of fasting on thyroid perform in each euthyroid and subtly hypothyroid individuals. Whereas there weren’t any research I might discover wanting on the results of intermittent fasting on clinically hypothyroid individuals, I feel we will make some inferences on fasting and hypothyroidism.

Suggestions for Fasting When You Have Thyroid Points

1. Be sure you’re replete within the thyroid-relevant vitamins.


  • Selenium: for changing T4 to lively T3
  • Iodine: for making thyroid hormone
  • Zinc: for thyroid perform

2. Don’t mix fasting with excessive calorie restriction.

What actually appears to destroy thyroid perform is continual calorie restriction—going “with out” for weeks, months, and years on finish. Your thyroid is all the time watching you, watching the alerts you ship. Feasting and fasting sends a sign of abundance. Decreasing energy by 20% for months sends the other sign, and diminished thyroid perform will be the end result.

Should you quick, be sure to eat sufficient meals if you really eat.

3. Should you’re hypothyroid however have it below management with thyroid hormone, fasting will in all probability give you the results you want.

Taking thyroid hormone the appropriate means successfully renders you euthyroid (regular thyroid perform). You’ll be able to proceed with fasting with out a lot fear; simply monitor your thyroid hormones and observe your subjective impression of the way it’s going.

4. Should you’re subclinically hypothyroid, fasting might be okay.

Analysis linked above reveals that folks with subclinical hypothyroid can profit from alternate day fasting (the place the “quick” day is definitely an excellent low-calorie day and the “fed” day includes consuming additional meals).

5. Should you’re hypothyroid and attempting to repair it naturally, lengthy fasting might be not a terrific thought.

Considered one of T3’s roles is to protect the muscle from atrophying during fasts. If in case you have low T3 and wish to deal with it naturally, launching right into a fasting routine will in all probability be counterproductive and will even pace up muscle loss. That is precisely what you don’t wish to occur throughout a quick.

Get the hypothyroidism dealt with earlier than you strive a critical quick (~24 hours+).

6. Should you’re hypothyroid and attempting to repair it naturally, shorter consuming home windows could assist.

I don’t advocate 24 hour+ fasts for hypothyroid sufferers going it alone, however I do assume there’s an argument for a shorter consuming window, particularly if that consuming window falls through the daylight.

Like all the pieces else within the physique, thyroid perform follows a circadian rhythm. Meals is a robust circadian entrainer. Should you’re consuming in any respect hours of the day and evening, or packing most of your energy late within the day and on into the night hours, this will throw off your circadian rhythm and your thyroid perform together with it.

Conversely, in case your consuming window is from 9 a.m. to five p.m., you’re consuming with the solar, which syncs your organic clock with the target daytime.

7. Watch out on the prolonged fasts.

I don’t advocate them for hypothyroid sufferers, however I do know you’re a curious, experimental bunch who will strive it regardless. If that’s you, be cautious. Take heed to your physique. Monitor your numbers. Don’t be afraid or really feel ashamed if you need to reduce the quick quick with a meal.

8. If it feels tense, it in all probability is.

Stress inhibits the conversion of T4 to T3, thereby lowering the extent of lively thyroid hormone in your physique. Don’t ignore stress, particularly if it’s the fasting that appears tense.

9. If fasting impacts your sleep, it’s in all probability affecting your thyroid.

Sufficient sleep is a naked minimal requirement for good thyroid perform. Some (however not all) individuals report worse sleep when fasting. Others (however not all) report higher sleep when fasting. This might go both means—simply be sure to know which means it’s affecting you and your sleep.

That’s about it. The topic isn’t as extensively researched as I’d like, and there’s a number of particular person variation, however we now have an honest quantity of information to go on and may make some first rate inferences. If in case you have any questions on fasting and hypothyroidism, ask down under. I can in all probability choose Elle Russ’ mind (the real thyroid expert around here) for some enter, too.

Take care, everybody!


Azizi F. Effect of dietary composition on fasting-induced changes in serum thyroid hormones and thyrotropin. Metab Clin Exp. 1978;27(8):935-42.

Burman KD, Smallridge RC, Osburne R, et al. Nature of suppressed TSH secretion during undernutrition: effect of fasting and refeeding on TSH responses to prolonged TRH infusions. Metab Clin Exp. 1980;29(1):46-52.


Akasheh RT, Kroeger CM, Trepanowski JF, et al. Weight loss efficacy of alternate day fasting versus daily calorie restriction in subjects with subclinical hypothyroidism: a secondary analysis. Appl Physiol Nutr Metab. 2020;45(3):340-343.

Ucci S, Renzini A, Russi V, et al. Thyroid Hormone Protects from Fasting-Induced Skeletal Muscle Atrophy by Promoting Metabolic Adaptation. Int J Mol Sci. 2019;20(22)

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