The Thyroid Condition Proven to Cause Weight Gain

Researchers show that hypothyroidism can cause excess weight gain

disappointed woman weighing herself on scale
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It is not uncommon for people to associate thyroid problems, more specifically hypothyroidism, with weight gain. In fact, weight gain is one of the most common symptoms of hypothyroidism –– and is what ultimately leads many people to their diagnosis.  

Proving the Thyroid Weight Gain Connection 

Researchers at the University of Birmingham in England have finally established what patients have known and many doctors have long denied –– being hypothyroid causes weight gain.

In a study reported in the journal Clinical Endocrinology, the researchers studied 162 people with hyperthyroidism for six months. Those who already were overweight, whose hyperthyroidism was caused by Graves Disease, or who had lost weight prior to diagnosis all had similar amounts of weight gain, which was approximately 5 to 5.5 kg (11 to 12 pounds) over the six months during which they were treated with antithyroid drugs for radioactive iodine.

Those who had their thyroid removed gained even more weight, an average of 10 kg (11 pounds). And those who became hypothyroid after treatment gained, on average, about 3 kg (6.5 pounds) more than those who were either transiently hypothyroid, or who never became hypothyroid at all post-treatment.

Overall, among the entire group, at the end up one year, weight was up by 3.95 kg (8.75 pounds), to 9.91 kg (22 pounds) after four years, with a mean weight gain of approximately 3.66 kg (8 pounds) per year.

The researchers concluded that there was substantial weight gain after treatment for hyperthyroidism, and those who became hypothyroid, despite levothyroxine treatment, gained the most weight.

Losing Weight With Hypothyroidism

If you have hypothyroidism, losing weight can be very challenging. Many people think that once you start taking thyroid hormone replacement medications, the weight will just fall off.

While these medications can help you lose the weight you have gained, that weight doesn't magically fall off –– it takes hard work, diet, and exercise

If you are struggling to lose weight, work with a nutritionist to find a dietary plan that works best for you. An optimal diet minimizes simple carbohydrates and sugars and focuses on lean proteins and vegetables. Diet alone may not be enough to kickstart weight loss. Getting seven to eight hours of sleep each night can also help you lose weight.

Exercise can also help you lose weight. Current guidelines from the Centers for Disease Control and Prevention (CDC) recommend adults get 150 minutes of moderate exercise and two sessions of muscle building each week. People with hypothyroidism may need to go beyond these recommendations to lose weight. 

If you have Graves disease or hyperthyroidism and are gaining weight or notice any other signs of hypothyroidism, speak to your doctor and have your thyroid tested. Other symptoms of hypothyroidism to keep an eye out for include:

  • Thinning hair 
  • Fatigue
  • Cold intolerance 
  • A hoarse or raspy voice 
  • Brittle nails 
  • Dry skin
  • Depression or inability 
  • Constipation 

These symptoms, as well as weight gain, may indicate that your current thyroid treatment is not optimal and needs to be reevaluated by a medical professional. Do not try and adjust your medication yourself. 


Dale, J., Daykin, J., Holder, R., Sheppard, M. C. & Franklyn, J. A. "Weight gain following treatment of hyperthyroidism," Clinical Endocrinology , 55 (2), 233-239.

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