Is Dieting Making You More Hypothyroid?

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Weight gain and fluctuations are a very common symptom of an underactive thyroid or hypothyroidism. However, many patients taking to dieting, i.e. cutting out calories or certain food groups in an attempt to shift pounds, are likely making their hypothyroidism worse. 

For many hypothyroid patients who go on low calorie and fad diets, they just don’t work. People either don’t lose weight, carrying on gaining weight despite dieting, or they lose the weight but soon gain it back, often with a few additional pounds on top to boot.

I’ve heard from literally thousands of thyroid patients who ask why this happens. And it’s quite simply because hypothyroidism is so involved with our metabolism and energy levels.

This scenario of being unable to lose weight and keep it off becomes even more common when someone repeatedly goes on low-calorie diets, fads, or struggles with yo-yo dieting (repeated loss and gain of weight).

What many thyroid patients don’t know is that chronic dieting can reduce Free T3 levels, the active thyroid hormone, causing the metabolism to slow down even further and weight loss to become even more difficult as time goes on. T3 is crucial for the functioning of every cell and function of the body, from brain function to bowel movements and energy. And the metabolism is in charge of our energy levels, production, body heat and thus, weight loss and gain.

Thyroid hormones play an important role in metabolic function. Whilst we need enough T3 to feel well and have a body that functions properly, reverse T3, an inactive form of T3, is an issue. Too much reverse T3 blocks the cell receptors for thyroid hormones, thus blocking the effect of the all important T3. If a patient has too much Reverse T3 in ratio to Free T3, then they are hypothyroid at a cellular level, which results in a reduced metabolic rate.

Studies have found that dieting can reduce metabolic function hugely. One particular study published in the American Journal of Physiology, Endocrinology and Metabolism, showed that even twenty-five days of restricting calories can result in a significant reduction of T3, due to less T4 converting to the T3. It resulted in a 50% reduction in T3, which, as already explained, affects everything including your metabolic function.

Unless the effects of chronic dieting are addressed, such as low T3 levels, excess Reverse T3 and even adrenal fatigue (which often drives reverse T3 levels up), attempts to lose weight and keep it off will often fail. Where a lot of thyroid patients struggle is even convincing their doctor to test Free T3 and Reverse T3 levels, which are very important. Addressing any non-optimal levels in these can help a lot of thyroid patients to not only lose weight if they wish, but also shift many other hypothyroid symptoms including fatigue, poor stamina, muscle aches and more.

There is also something called your weight ‘set point’ which you should take in to consideration. Discussed frequently in thyroid forums and support groups, your ‘set point’ is the brain’s target weight for you. It is therefore individual. Just as the body aims to maintain a normal body temperature, it also works to maintain a body weight that is physiologically comfortable. The ‘set point’ is maintained by the hypothalamus and is often genetically influenced, however, a number of things can cause this ‘set point’ to change, including making it a higher or lower number. Chronic dieting is the main cause for an abnormal ‘set point’, whereby it can result in slower metabolism as explained previously.

Ways to address this can include reaching optimal thyroid levels, a more consistent diet and calorie intake (no more yo-yoing, fad diets or calorie restrictions), consistent exercise (no more overexercising followed by needing to heavily rest due to the damage going too far does) and managing your Hashimoto’s.

When it comes to weight gain and weight fluctuations with hypothyroidism, I do understand the frustrations. My weight has fluctuated quite a lot with hypothyroidism and what I’ve learnt in my bid to try and lose weight with frequent yo-yo dieting and calorie restrictions, is that my physical health is so much more important than how I look in the mirror, or my weight alone. Often, if we focus on feeling physically well, such as reaching optimal thyroid levels, vitamin levels and ensure good adrenal health, our bodies shed any extra pounds that it doesn’t want anyway.

I just want thyroid patients to be aware that often, dieting and calorie restrictions place extra stress upon the body, that it just doesn’t need when it’s already balancing chronic illnesses and hormone imbalances such as hypothyroidism.

As well as the studies that demonstrate how dieting can in fact make you more hypothyroid, the effects of denying yourself adequate fuel in the form of food, can include fatigue, drowsiness, blood sugar imbalances, mental health risks and more, in terms of physical proof. You’re not likely to recover from your health conditions if you’re denying it adequate nutrition and fuel.

Disclaimer: Since learning about body positivity and now practising it myself, I want to just leave a statement expressing that weight is not the be all and end all. It doesn’t make you any less worthy of love, happiness or anything else in life. Weight gain is natural – bodies change all the time – but I do appreciate that for many, the weight gain associated with hypothyroidism can be another frustrating reminder of how it affects your life and takes control from you. However, if you wish to pursue weight-loss, I can’t stop you and I respect your decision. Just know that you can be happy with how you are and make peace with your body. We are battling a difficult health condition which directly affects our metabolic function and energy levels, after all. 

You can click on the hyperlinks in the above post to learn more and see references to information given, but more reading and references can also be found at:

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Written by Rachel, The Invisible Hypothyroidism

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Rachel Hill, Thyroid Patient Advocate, blogger and author, has Six 2018 WEGO Health Award Nominations. She is a highly ranked writer appearing in the Top Hypothyroidism Websites and Top Thyroid Websites and has worked with The National Academy of Hypothyroidism, The BBC, The Mighty, Yahoo, MSN and ThyroidChange, to name just a few. She is well-recognised as a useful contributor to the thyroid community and also contributed the foreword to Emily Kyle’s The 30-Minute Thyroid Cookbook.

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