Dieting with an underactive thyroid

I have been trying to loose weight for about 6 weeks, together with going to the gym 3 times a week. Cutting down on food has sometimes made me feel really strange, especially waking up in the middle of the night with hunger pains.

Is it my metabolism not being regulated or is just the symptoms of dieting? I try to eat the correct amount of calories and drink enough fluids, my husband tells me that's all in my head.

7 Replies

  • "In your head' - nothing of the sort. It is well known that many who are on levothyroxine gain weight (not everyone of course). In hypo, if we are not on the optimum medication, our metabolism is too low to start with, so if we lower our food intake, it will drop even further. Some of our members have even gained weight whilst dieting! Also unexplained weight gain is a clinical symptom many have before they are diagnosed with hypo.

    If we are healthy and overweight (normal metabolism) we can reduce food plus exercise and be happy to lose around 1 or 2-lb a week.

    Many of the doctors who were taught medical symptoms of thyroid gland problems alone (no blood tests in those days - they also prescribed NDT) have said that nowadays our medication is too low to make us well.This is a link:-

    and another

  • One really shouldn't diet with an Under-active thyroid. The weight-gain is not due to what you eat, it is due to low thyroid. You need a relatively high number of calories to support your conversion of T4 into T3. You need to eat fat and salt and quite a bit of protein.

    Going to the gym is also a bad idea because it uses up those calories that you need for conversion - forget calories in vs calories out when your hypo, it just doesn't work that way anymore. Exercising also uses up your T3 and you haven't got enough to spare.

    Neither dieting nor exercising are going to make you lose weight when you're hypo. And they are probably going to make you more hypo. Don't allow yourself to get hungry, that isn't good for you. Eat plenty of fat, that fills you up and stops you getting hungry in the middle of the night.

    What is going to work is getting your T3 up to the top of the range. Do you have any labs to share with us? What are you taking, and how much?

    Hugs, Grey

  • Thanks for your advice I will take on board what you have told me. I will try to get me lab results next time I am at the doctors. There are two reasons why I need to lose weight 1. My BMI is high 2. My blood pressure/ heart beat is high.

    So I thought it would be a good idea to see if this would improve my general health.

    I take 75g of Levothyroxine.


  • Isn't high blood pressure a symptom of hypothyroid. Do you feel your face is puffy? When your being successfully treated with the optimum dose of Levy or NDT, you will find: 1. your puffy face (not saying you have one) slims down considerably and skin improves. 2. Your muscles will improve on their own, without exercise, and when you are feeling better, when you do exercise, your muscles actually get toned more.

  • 75 mcg Levo is not a very large dose. You more than likely need an increase. That is why you can't lose weight. You are not going to lose it unless your levels are optimal for you. And you're not going to feel well, either. Your general health is suffering because you are Under-treated.

    High blood pressure and heart beat are symptoms of low thyroid, another thing that tells me you need an increase.

    I realise all this is confusing and difficult, and even doctors don't understand it. Doctors tend to keep you ill by dosing by the TSH. This just doesn't work. You need to get your FT4 and FT3 tested too. But you might have a battle on your hands trying to get those done! lol

    Hugs, Grey

  • Thanks for your advice, how do ask the doctors about these tests and how do explain why I want them done? When I get the results what will it tell me? Sorry to be so ignorant !

  • T4 is the main thyroid hormone, but it is a storage hormone and can't be used by the body without being converted into T3. T3 is the active hormone and the most important one. Every cell in the body uses it. So when you don't have enough, all sorts of things can go wrong.

    You want them done because you need to know at what level they are before adjusting your dose in either direction. You cannot be over-medicated (and need to lower the dose) unless the T3 is over-range. I'm going to take a guess that your T3 is pretty low, and that's why you can't lose weight.

    Also, testing those two hormones gives you an indication as to whether you are able to convert the T4 you are taking into the T3 that you need. If you can't convert, then you need to take T3 (Cynomel/Cytomel) rather than Levo.

    Please do not apologise for being ignorant! None of us are born knowing about thyroid. And, unless we need to, we are not going to learn about it. We all start out ignorant. The problem is, doctors stay ignorant, and after a while, the patient knows more than the doctor. Which puts us in a difficult position. But cross that bridge when you come to it. First of all, learn all you can. Know your disease! It's the only way to over-come it.

    Hugs, Grey

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