Does thyroid disease cause weight gain?

thyroid weight gainOne of the most common questions I have been asked as a thyroid specialist is “Does thyroid disease cause weight gain?”.

The answer is simple, thyroid disease may cause weight gain, but not always. However, the weight gain from thyroid disease is never, ever massive. If you’ve put on 12 kilos over a year, it’s impossible that thyroid disease is causing this.

Why is that?

It’s because thyroid disease never causes rapid, massive weight gain. In fact most people with thyroid disease have had it for years before it’s actually diagnosed.  The symptoms you can get such as tiredness, dry skin, low mood and weight gain are very subtle. Most people think it’s due to other causes, such as changes in their life.  Because thyroid disease takes years to develop,  the weight gain too is gradual. Even if you did gain weight, treating thyroid disease usually doesn’t make you go back to your original weight quickly.

How much weight can I put on if I have thyroid disease?

The weight gain in hypothyroidism is actually due to an accumulation of salt and water rather than fat. According to the British Thyroid Foundation, the most you can lose from treating hypothyroidism is 10% of your existing weight, and that too in extreme cases. The American Thyroid Association states that up to 5-10 pounds of weight gain may be due to  thyroid disease (at the most). However, the key thing to keep in mind is that this depends on the severity of the hypothyroidism. If you only have mild thyroid disease, you may not have any weight gain at all due to this condition.

Many people who come to my clinic are convinced that their thyroid gland is causing weight gain. They sometimes find it difficult to believe it might not be so. If your thyroid hormones are normal and you are still gaining weight, your thyroid gland can’t be the cause. This is true if you are on thyroid medication or not. In fact if your thyroid hormones are normal, as far as your endocrine system is concerned you have a normally functioning thyroid gland (even if you have to take thyroid tablets). This is because the endocrine system cannot distinguish between normal hormone levels from a normal gland and that from a person taking the correct dose of thyroid tablets.

What can I do if my weight loss is not due to thyroid disease?

Most people are extremely disappointed to hear their weight gain is not due to thyroid disease. However, you don’t need to get frustrated. In fact, it’s very good that you don’t have to worry about your thyroid causing weight gain. If weight loss is your goal, a much more useful approach is focusing on what else can be causing it. Perhaps you need to rule out Polycystic Ovarian Syndrome other conditions causing weight gain. You can read more about them on this site. You may be surprised to hear that the number of medical diseases that cause weight gain is actually very small. It may be a cliche, but to lose weight the most important step would be carefully reviewing what you eat. Perhaps there are some hidden calories in a food item you thought was “healthy”.

From my experience once medical conditions have been excluded, massive weight gain (20 kilos over a few years) is usually due to poor diet, lack of exercise, genetic factors or a combination of 2 or more of these factors. It’s unfortunately not what most people want to hear, but understanding this may hold the key to achieve genuine and long-lasting weight loss.

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