The FastDay Forum

Are there any studies out the that show the affect of fasting on those who suffer thyroid problems?

Mine is under active and wondered if IF would improve its level

Em x

I am also under active, and will be interested to hear from some knowledgable person too.

Well I had a look on pubmed (the database of scientific papers) and couldn't find anything about fasting and thyroid function. I'll try again when I have time...

Hi, as far as I know there is no effect of moderate weight loss or intermittent fasting on thyroid function. However, if you are using thyroid hormone substitution, the medication works best when taken on an empty stomach. If you usually take your meds with or after breakfast (which you preferably shouldn't), taking in on an empty stomach while fasting will increase the amount of thyroid hormone in your blood.
That being said, if you are fasting two days out of seven, I'm not sure this would be a problem.
Disclaimer - if you have other problems such as extreme obesity or diabetes 2, things might work differently. In that case I would recommend involving your GP anyhow.

I'm surprised at the number of people who don't know that thyroxine should be taken on an empty stomach.
My leaflet says to take it at least 1/2 hour before eating.

I have also searched for information on this and found nothing. My thyroid is hyperactive, and I have to take medication to calm it down. I had a blood test in December, started IF on January 8 and I have another blood test scheduled in 4 weeks - so I am interested to see if there has been any effect. Of course any change doesn't prove anything, as a sample of 1 isn't a sample at all. But I'm hoping that doing something healthy that has such widespread benefits may also benefit this as well.

My wife has an under active thyroid and takes thyroxine. Before starting 5:2 her dose was 125mcg, It's been at this level for 8 years. At her last review and after 6 months of this diet, the dose was cut to 100mcg.

We have no idea whether the reduction is down to the weight loss or diet or something else, but taking less drugs is a step in the right direction.

mole3 wrote: My wife has an under active thyroid and takes thyroxine. Before starting 5:2 her dose was 125mcg, It's been at this level for 8 years. At her last review and after 6 months of this diet, the dose was cut to 100mcg.

We have no idea whether the reduction is down to the weight loss or diet or something else, but taking less drugs is a step in the right direction.

Just out of interest - how much weight did she loose?

mole3 wrote: My wife has an under active thyroid and takes thyroxine. Before starting 5:2 her dose was 125mcg, It's been at this level for 8 years. At her last review and after 6 months of this diet, the dose was cut to 100mcg.

We have no idea whether the reduction is down to the weight loss or diet or something else, but taking less drugs is a step in the right direction.

Really interesting experience, thanks for posting your wife's experience.

I have an underactive thyroid and am also on 125mcg levothyroxin a day. I started the diet last August, but since Christmas, I have had exactly the same symptoms that I had when my thyroid condition was first diagnosed. I have just arranged to have a blood test to check the levels to see whether something has happened to the thyroid levels.

Would be interested to know whether the diet has somehow kick-started my thyroid again or whether some other factor is at work.

Thyroxine dosage is directly related to weight. My doctor said if I choose to have my thyroid killed with radiation, and get put on thyroxine, the dose will have to change whenever weight goes up or down.

He said 10 lbs of weight loss or gain will affect the dose.

Coffecat wrote: Just out of interest - how much weight did she loose?

19 lbs

That could well explain it Tracie, it would be interesting to find out fournarios weight loss and dosage change if any.

I have no thyroid gland. I had Hashimoto's nodules 30 years ago and had a thyroidectomy. Since then I have fasted on many occasions, not specifically to lose weight but for spiritual reasons (a 10 day Buddhist silent retreat). I also undertook a 28 day juice fast a couple of years ago as I had been reliably informed that it was beneficial for arthritis and inflammatory conditions but, in fact, it didn't make any difference sadly and it was gruelling.

Anyway, my experience of fasting is that it had no effect on the the thyroid equilibrium. That may be because I have no thyroid tissue remaining and so my condition is completely controlled (or not!) by hormone replacement medication. After 30 years on Thyroxine I swapped this year to T3 which I am finding suits me much better. The NHS do not approve and are threatening to stop prescribing (down to cost) - that's a whole different issue and one I feel very strongly about so let's not go there!!

My understanding is that if thyroid tissue is still present it can indeed be reactivated and begin to produce thyroid hormones in which case your medication would need to be adjusted accordingly. I believe (and I am not alone) that the standard thyroid testing is woefully inadequate and that Thyroxine is insufficient to fully compensate for a failing thyroid. Weightloss will also have an effect on the amount of thyroid hormone you need.

It can be more challenging to lose weight if your thyroid is underactive but it can be done. I've struggled with my weight for years and have been doing 4:3 for the past 4 weeks and have lost 10lbs so am very pleased.

Ah Marla - thank you for sharing your experience and congrats on your weightloss!

Mole - I'm very curious to see how we respond, those of us who still have thyroids. I know a sample of three or four isn't exactly a scientific sampling, but our anecdotal evidence may lead toward a real study someday

Tracieknits wrote: Thyroxine dosage is directly related to weight. My doctor said if I choose to have my thyroid killed with radiation, and get put on thyroxine, the dose will have to change whenever weight goes up or down.

He said 10 lbs of weight loss or gain will affect the dose.

How strange as my gps have never even mentioned weight is related to the dose.

Would love to get it working again