Thyroid Health: How it Plays a Role in Weight Maintenance

By Lizzie Streit, MS, RDN, LD 

At the base of the neck, just below the voice box, sits a butterfly-shaped gland that has several important functions in the body.  

Known as the thyroid gland, this organ produces hormones that play a large role in metabolism, growth, and temperature and energy regulation.  

If the thyroid gland is not functioning properly, it may result in weight gain or loss, among other symptoms. 

This article provides an overview of thyroid functions, types of thyroid diseases, and how thyroid health plays a role in weight maintenance. 

Functions of the Thyroid Gland 

The thyroid gland produces three important hormones (1): 

  • Triiodothyronine (T3) 

  • Thyroxine (T4) 

  • Calcitonin 

Both T3 and T4 help regulate metabolism. Specifically, these hormones increase the activity of every cell in the body by increasing the basal metabolic rate (BMR), or the rate at which the body uses energy while at rest (1).  

The increase in BMR leads to a rise in body temperature, faster pulse, quicker use of energy from food, proper growth and development in children, and improved concentration (1).  

When the thyroid is functioning properly, so is the body’s metabolism, temperature regulation, and energy production. A healthy thyroid helps you use calories efficiently and therefore maintain a healthy weight. 

The thyroid gland uses iodine, a mineral found in some foods, to make T3 and T4. It receives signals from the pituitary gland in the brain, in the form of thyroid-stimulating hormone (TSH), that dictate how much T3 and T4 it should release (1). 

Calcitonin is a hormone that regulates bone formation and calcium and phosphate levels in the blood. It does not play a role in metabolism (1). 

Types of Thyroid Diseases 

When the thyroid produces excessive or inadequate amounts of hormones, metabolism can be greatly affected.  

The following issues can impact the thyroid and the important functions it has in the body (2): 

  • Hypothyroidism (underactive thyroid): low production of thyroid hormone; can be caused by Hashimoto’s disease (an autoimmune condition), medications (such as lithium), iodine deficiency, thyroid cancer, and others 

  • Symptoms: sluggishness and lethargy, weight gain, feeling cold, dry skin, slow heart rate 

  • Hyperthyroidism (overactive thyroid): high production of thyroid hormone; can be caused by Graves disease (an autoimmune condition), medications (such as those containing iodine), and others 

  • Symptoms: irritability, rapid heart rate, weight loss, anxiety, abnormal protrusion of the eyes 

  • Thyroid cancer: an irregular, cancerous mass on the thyroid that impacts function 

  • Symptoms: lump and swelling in the neck; trouble swallowing; hoarseness 

  • Goiter: an enlargement of the thyroid gland; most commonly caused by iodine deficiency 

  • Symptoms: visible swelling and enlargement; may not have many other symptoms 

  • Thyroid nodule: a lump that grows in the thyroid 

  • Symptoms: usually none besides enlargement 

  • Pregnancy and thyroid issues: having a child can lead to postpartum hyper- or hypothyroidism, but it can be difficult to diagnosis 

Hypothyroidism and Weight Maintenance 

As noted above, hypothyroidism can lead to weight gain. 

This is because thyroid hormones are so vital in increasing BMR and helping the body use calories from food. So, an underactive thyroid can contribute to a sluggish metabolism and a subsequent increase in body weight.  

What’s more, having low energy as a result of hypothyroidism may make you less likely to exercise or prepare healthy meals, and may increase cravings for carbohydrates and sugar that provide quick energy. This can also lead to weight gain.  

Due to these reasons, long-term hypothyroidism may be a risk factor for obesity, but the link between these two issues is not well understood (3). 

Medical Treatments for Hypothyroidism  

If you are experiencing weight gain and other symptoms related to hypothyroidism, such as sluggishness, cold intolerance, and a slow heart rate, be sure to visit your doctor as soon as possible. 

Getting a proper diagnosis for hypothyroidism is the first step in pursuing treatment that can help with symptom relief.  

Levothyroxine, a synthetic form of T4, is commonly used to treat hypothyroidism. Since it helps stabilize thyroid hormone balance in the body, it may promote modest weight loss and help some people get back to their normal weight (2). 

But whether or not levothyroxine helps with weight loss depends on the dose and person. High doses of levothyroxine, which may lead to more weight loss compared to lower doses, are not typically recommended and can cause unpleasant side effects. 

Dietary Recommendations for Hypothyroidism 

In addition to medications, there are some dietary and lifestyle recommendations for the management of hypothyroidism. 

Once your thyroid hormone levels are stabilized with the help of medication, eating a healthy diet and increasing physical activity can help you lose the weight that you may have gained before your diagnosis. 

However, it’s important to note that dietary recommendations should be individualized based on the causes and symptoms of hypothyroidism in each person, with the help of a registered dietitian. 

Here are some of the general diet and lifestyle recommendations for individuals who have hypothyroidism (4): 

  • Overall, eat a mostly plant-based, balanced diet with a variety of vegetables, lean proteins, fruits, legumes, and other nutritious foods. 

  • Include foods with nutrients that may promote proper thyroid function, such as iodine (found in iodized salt, dairy, and shrimp) and selenium (found in brazil nuts, tuna, and crab). 

  • However, supplemental forms and/or excessive intake of these nutrients is not recommended. 

  • Limit foods that decrease thyroid hormone synthesis, such as cruciferous vegetables (broccoli, cauliflower, brussels sprouts, cabbage) and soy. 

  • However, this may not be as much of a concern for some people. 

  • Incorporate regular physical activity and exercise into your daily routine. 

  • Current recommendations from the American Heart Association suggest 150 minutes of moderate intensity activity per week (5). 

  • Manage stress through yoga, exercise, and other techniques. 

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Stef Keegan