The FastDay Forum

Hi there, underactive thyroidian here too.
I'm on alternate days, 100mg thyroxine, then 75mg next day.
I've been doing this diet for 5 weeks (5 stone to lose,goal-1 stone at a time)
and have lost 11lbs so far, and feeling very good, my clothes are already getting nice and baggy, yayyyy! so yes i think its possible to have underactive thyroid and for this to work.
I've had 1 week when I lost nothing at all, but the rest has been a loss.
For me, I find drinks all day, perhaps a piece of fruit at lunch time, or a cuppa soup if I really can't wait, but then have protein/veggies for dinner.
The first day was the hardest, but not that hard really.
My Mum's on thyroxine too and doing this diet, she's lost 9lbs so far.
Keep going! Find what suits you, enjoy your treats on feasty days.
Let us know how you're doing.

Hi the Bevster,
Thanks for that post, it gives us hypothyroiders a lot of encouragement to keep going even though some of our losses our really slow ( mine included! ) when you start to wonder whether its worth going on, this gives us hope that it will work for us too even though it may take us longer to get the end result ie., slim! This is only my third week and although I didn't lose last week, I have lost 4 lbs in the first week so at least that's a start! Good luck to you and your mum.xx

Are the standard TDEE guesstimators valid for underactive thyroid ? I read a paper where the mean RMR of such people was 1200 with some in the 1,000 area.

That sounds pretty gloomy, Phil. That could mean a weekly calorie count of 6000 (5 x 1000 + 2 x 500) as against 11000 (5 x 2000 + 2 x 500) for someone with hypothyroidism. Can that be right?

Looking around, I found a couple of papers that might be relevant:

http://www.ncbi.nlm.nih.gov/pubmed/3959900

http://www.lifeextensionvitamins.com/thde.html

This is a general look at the thyroid, so I've extracted the relevant paragraph:

"Thyroid Deficiency in Obesity and Diabetes

The enzyme that converts T4 to T3 is called 5-monodeiodinase. Unfortunately, this enzyme is inhibited in response to diminished caloric intake (dieting). That means that the fewer calories ingested, the lower the production of 5-monodeiodinase. This is the body's natural method of conserving fuel during shortage. Because "dieting" is not a natural state, it elicits the same physical reaction as famine--another reason why "eating less" will never effectively treat obesity. Deficient peripheral conversion of T4 to T3 is found almost universally in patients who become overweight."

That whole T4 to T3 conversion thing has merit, the question is what needs to be done to help the body convert better? I have my endocrinologist appt on May 1 so we'll see how my thyroid panel is looking then after doing 5:2 for approximately 2 months. Right now I'm on 200mcg of Synthroid. Yes it's a rather high dose, which baffles my endo, but its what it takes to keep my TSH suppressed since I had thyroid cancer. I've read where some people do much better adding T3, which I'm inclined to ask about to see how my dr feels about that.

[carorees]

Are the standard TDEE guesstimators valid for underactive thyroid ? I read a paper where the mean RMR of such people was 1200 with some in the 1,000 area.

That sounds pretty gloomy, Phil. That could mean a weekly calorie count of 6000 (5 x 1000 + 2 x 500) as against 11000 (5 x 2000 + 2 x 500) for someone with hypothyroidism. Can that be right?

Looking around, I found a couple of papers that might be relevant:

http://www.ncbi.nlm.nih.gov/pubmed/3959900

http://www.lifeextensionvitamins.com/thde.html

This is a general look at the thyroid, so I've extracted the relevant paragraph:

"Thyroid Deficiency in Obesity and Diabetes

The enzyme that converts T4 to T3 is called 5-monodeiodinase. Unfortunately, this enzyme is inhibited in response to diminished caloric intake (dieting). That means that the fewer calories ingested, the lower the production of 5-monodeiodinase. This is the body's natural method of conserving fuel during shortage. Because "dieting" is not a natural state, it elicits the same physical reaction as famine--another reason why "eating less" will never effectively treat obesity. Deficient peripheral conversion of T4 to T3 is found almost universally in patients who become overweight."

I feel that this is why I get better weight loss when I eat more on feast days (as long add I don't eat over TDEE on average) and certainly suggests that reducing calories on feast days may not be the answer to stalled weight loss.

The RMR (resting metabolic rate) is only part of the TDEE of course, TDEE will be at least 20% more than that "However, a recent review of global
DLW data (Black et al, 1996) suggests that PAL for normally active free-living people are higher than 1.55 in all age-sex groups except those over 75y"

so even 1000 RMR suggests 1550 TDEE.
http://europepmc.org/abstract/MED/9192200

REE/FFM = 27.4–2.53 × log TSH is a regression fit to the effect of manipulating TSH levels in 9 female patients on chronic treatment with thyroxine.

Tabulated data shows individual Resting Energy Expenditure (REE) and Fat Free Mass (FFM) with REE as low as 1078 and up to 1700 kcals/day (subject 5, who seemed to have generally high metabolic rate).

http://jcem.endojournals.org/content/82/4/1118.full

Bevster, thanks for posting this as its nice to know someone with thyroid problems is doing really well on this plan, you must be so pleased!! I am sorry to say I did my 7th weigh-in on the weekend and no loss again so that's 4 straight weeks with no loss.
Today is one of my fast days so instead of my usual 500cals I am going to reduce down to 300 and have a small meal this evening. Hopefully if I do that on my 2 fast days this week it might show in some sort of loss at my next weigh-in

I haven't been doing the 5:2 for that long (on Wednesday -9th day- I will inform you regarding my weekly progress since I won't be able to weigh meself tomorrow) but I can assure you that the TDEE is a worthless number for those with a thyroid that isn't working properly. My TDEE is 1764. I never eat more than 1200-1300 calories if I don't want to get super-fat.
I used it to calculate the calories that I'm supposed to eat on fast days (1764/4=441) but on my non fast days I most certainly eat quite less than 1764.

TDEE is never a worthless number, though the estimators are only accurate to +/-10% for about 70% of the healthy population and so as you say can be a mile off if you have a medical condition that affects the metabolism.

As I said, it is a worthless number for those with a thyroid that isn't working properly.

As I said, it is a worthless number for those with a thyroid that isn't working properly.

Well your Total Daily Energy Expenditure (TDEE) will be lower with a thyroid problem, but it's still the amount of energy you are expending, surely ?

How can it be worthless ?

[carorees]

I think TML meant that the TDEE calculators are worthless. Obviously if an accurate estimate of TDEE could be made it would be useful. But it seems that TDEE can be highly variable for people with thyroid problems. Now if you could find a paper that could give a correction factor that could be applied to the standard formulas, that would be useful!

Well, so far, the only way to calculate my "official" TDEE are the online calculators and indeed the number that they offer is worthless since it's quite higher than my experience says I can eat.
My doctor explained that the only way to find what the TDEE of a person with thyroid problems is to write down what we eat and weigh ourselves everyday and keep a diary. And even this is not 100% accurate because the problem of water retention comes in, plus the fact that the thyroid doesn't malfunction in the same way everyday.
So, all we can do is estimate an... estimation. I know that this might sound a bit weird to those who don't have this problem but sadly that's way it is, or -to be fair- that's the way it is with me.
My TDEE is over 1700 calories, I never ate more than 1500 and when my thyroid took its last nasty turn I gained 4 kilos in less than 15 days. Obviously, my TDEE is worthless for me... Or, to be more specific, I have a different TDEE which is based on daily observations and will change many times in my life depending on my thyroid's intentions.

I have underactive Thyroid too, I am on 50mg Eltoxin (danish brand maybe) and have been on this for 5 years. Have difficulties in loosing weight, so I hope at least that this diet will speed my weightloss - just a litle bit.