An underactive thyroid can cause modest weight gain, much of it salt and water rather than body fat. The British Thyroid Foundation states that treatment can be expected to produce a small weight loss, usually less than 10% of body weight, and that no significant weight loss is fairly common. The American Thyroid Association gives general guidance that, once thyroid levels are normal, the ability to lose weight is generally the same as for people without a thyroid problem.
- An underactive thyroid slows metabolic rate, and Cleveland Clinic lists weight gain among its common symptoms, alongside fatigue and feeling cold.
- The British Thyroid Foundation states that, depending on severity, around 5 to 10 pounds (roughly 2 to 4.5 kg) of body weight may be attributable to the thyroid.
- The British Thyroid Foundation also states that treating hypothyroidism can be expected to produce a small weight loss, usually less than 10% of body weight, and that no significant weight loss after successful treatment is fairly common.
- Weight that remains once thyroid levels are normal can be addressed with the same approach as any other weight, including protein, resistance training and a gradual pace.
- Taking extra thyroid hormone to lose weight is not a safe or effective treatment, and the American Thyroid Association warns that it can cause side effects including loss of muscle and bone.
- If weight does not change despite a normal thyroid-stimulating hormone (TSH) result, we recommend further investigation, because insulin resistance, PCOS and certain medications can also affect weight.
Many patients hope that treating an underactive thyroid will lead to significant weight loss. Our page on thyroid and weight loss covers how our endocrinologists assess and treat thyroid conditions.
Does an underactive thyroid cause weight gain?
It can, and the amount is often modest. The thyroid gland produces hormones that help regulate metabolic rate, and when it produces too little, a condition called hypothyroidism, the body uses energy more slowly. Cleveland Clinic lists weight gain among the common symptoms, alongside fatigue, feeling cold, dry skin and hair, and difficulty concentrating. It names Hashimoto disease, thyroid surgery, radiation treatment and certain medications among the causes.
The British Thyroid Foundation states that, depending on how severe the hypothyroidism is, around 5 to 10 pounds (roughly 2 to 4.5 kg) of body weight may be attributable to the thyroid. It adds that most of that extra weight is an accumulation of salt and water rather than fat. A larger gain generally has other contributors, and your endocrinologist will assess these as well.
How much weight can treating the thyroid help you lose?
The amount is often smaller than patients expect. The British Thyroid Foundation states that treatment for hypothyroidism can be expected to produce a small weight loss, usually less than 10% of body weight, and that it is fairly common to find no significant weight loss after successful treatment. The American Thyroid Association gives general guidance that, once thyroid hormone levels are in the normal range, the ability to gain or lose weight is generally the same as in people without a thyroid problem, although individual responses vary.
Treatment with levothyroxine, a daily thyroid hormone replacement, corrects the underactive thyroid. It does not by itself reverse weight gained for other reasons.
Why is some of the weight fluid?
In hypothyroidism the body tends to retain salt and water, which contributes to the puffiness some patients notice in the face and around the eyes. The British Thyroid Foundation and the American Thyroid Association both state that much of the weight gained in hypothyroidism is salt and water. When treatment starts, part of the early change on the scale is the loss of that fluid.
The first weeks of thyroid treatment can therefore show a small, quick change on the scale that then slows. At Endocare, body composition analysis is included free of charge at every consultation. Body composition analysis estimates body fat, muscle mass and body water. Repeated measurements help your endocrinologist understand how your body is changing beyond the number on the scale. Our article on the difference between fat loss and weight loss explains how to tell them apart.
Why might your weight not change when your TSH is normal?
Thyroid-stimulating hormone (TSH) is the main blood test used to monitor thyroid treatment. Once your TSH result is normal, other factors can still affect your weight. If your weight does not change once thyroid levels are normal, we recommend investigating further. Insulin resistance can also make weight loss more challenging and is often associated with increased waist circumference. Polycystic ovary syndrome (PCOS) affects around one in ten women of reproductive age and can influence weight and metabolism. Certain prescription medications can also contribute to weight gain.
Sleep, stress, physical activity and eating habits can also affect weight. In some patients, other hormonal conditions may contribute. Your endocrinologist will review your blood tests, including thyroid function, glucose and insulin markers, alongside your history and your body composition analysis.
What works alongside thyroid treatment?
Protein and resistance training
Adequate protein and resistance training can help preserve muscle while you lose weight. A review in the journal Nutrients concluded that higher protein intakes help protect fat-free mass and skeletal muscle mass during weight loss, either on their own or together with exercise. General guidance such as the International Society of Sports Nutrition suggests roughly 1.2 to 1.6 g of protein per kg of body weight per day for people losing weight. Endocare’s lifestyle coaches will personalise that figure from your body composition analysis. Two to three resistance training sessions a week can help preserve muscle during weight loss.
Realistic pace
The US Centers for Disease Control and Prevention states that people who lose weight at a gradual, steady pace of around 0.5 kg to 1 kg a week are more likely to keep it off than people who lose it faster. Your endocrinologist will review your rate of weight loss alongside your thyroid results at each follow-up.
We do not recommend iodine supplements or other thyroid supplements as a weight loss treatment. Taking extra thyroid hormone to lose weight is not safe. The American Thyroid Association warns that excess thyroid hormone can cause side effects including heart rhythm problems and loss of muscle and bone, and that weight lost this way is often regained.
Is weight loss medication appropriate with a thyroid condition?
For many patients with treated, stable hypothyroidism, a thyroid condition does not by itself rule out weight loss medication, and the decision follows the same assessment as for any other patient. Our endocrinologists prescribe weight loss medication for patients with a body mass index above 30, or above 27 where there is a weight-related condition such as type 2 diabetes, hypertension or high cholesterol. Our article on who qualifies for weight loss injections sets out the criteria and the conditions your endocrinologist checks before prescribing.
Some thyroid conditions are among the points the prescribing information asks doctors to assess before starting a GLP-1 medication. Your endocrinologist will therefore review your thyroid history in full at the first consultation. Patients should not decide by themselves to start a GLP-1 medication. A doctor’s review is critical to ensure the treatment is safe and appropriate for the individual.
What does Endocare check?
Your first appointment is a full medical assessment, not simply a prescription visit. Your endocrinologist will take a full medical history, review your thyroid function and your other blood tests, and examine you before discussing treatment options. Your endocrinologist will review blood tests from the last three months before prescribing. If your results are out of date, the clinic can arrange the required tests.
Thyroid conditions are a core part of an endocrinologist’s specialty, so your endocrinologist will assess the thyroid and the weight together. Monthly follow-up appointments can be held in person at the clinic or online. We recommend the first consultation in person, as it includes a physical examination and body composition analysis. Obesity is common in the UAE. The UAE National Health Survey 2017 to 2018, published by the Ministry of Health and Prevention, found that 27.8% of adults aged 18 to 69 had obesity, and a thyroid condition can occur alongside the other causes of weight gain.
Frequently asked questions
Does hypothyroidism cause weight gain?
It can, and the amount is often modest. The British Thyroid Foundation states that around 5 to 10 pounds (roughly 2 to 4.5 kg) may be attributable to the thyroid, depending on severity, and that most of it is salt and water rather than fat.
How much weight will I lose once my thyroid is treated?
The amount is often smaller than expected. The British Thyroid Foundation states that treatment can be expected to produce a small weight loss, usually less than 10% of body weight, and that no significant weight loss after successful treatment is fairly common. Weight that remains once your thyroid results are normal can be addressed with the same approach as any other weight.
Why has my weight not changed even though my TSH is normal?
Your TSH result can be normal while other factors still affect your weight. Insulin resistance, PCOS, certain medications, sleep and eating patterns are among the factors your endocrinologist will review.
Is some of the weight fluid?
The British Thyroid Foundation and the American Thyroid Association both state that much of the weight gained in hypothyroidism is salt and water. Part of the early change after treatment starts is the loss of that fluid, and body composition analysis can help distinguish it from fat loss.
Can I take weight loss medication with a thyroid condition?
For many patients with treated, stable hypothyroidism, yes, after a full assessment. Your endocrinologist will review your thyroid history, your other conditions and your medications before deciding whether a medication such as Mounjaro, Wegovy or Foundayo is appropriate for you.
What should I have tested?
Thyroid function, glucose and insulin markers, and a lipid profile are a common starting point, alongside a body composition analysis. Your endocrinologist will decide which tests you need.
If you are on thyroid treatment and your weight has not followed, or you suspect your thyroid is affecting your weight, the first step is a consultation. Your endocrinologist will review your thyroid function, your other blood tests and your body composition analysis, and will set a plan for both.
You can speak to an endocrinologist at our clinics in Dubai and Abu Dhabi.
