The thyroid gland's role in weight loss

Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer

With the return of summer and lighter clothing, thousands of people are looking to lose weight and slim down. The web is full of advice on diet and exercise to do just that. While loosing weight is rarely an easy endeavour, physiological conditions make it more difficult, if not impossible for many people, and a poorly-functioning thyroid gland is often overlooked.

The thyroid gland – a major control center

The thyroid gland affects many vital body functions, including energy levels, muscle strength, heart rate, calorie burn rate and digestion. [1] [2] To understand its role, here are a few definitions:

Metabolism

Metabolism is the set of chemical reactions that occur inside each of our cells to keep us alive: energy production from nutrients to maintain breathing, heartbeat, brain function, reproduction, body temperature, digestion, work and exercise, etc.

Basal metabolic rate

On the other hand, basal metabolism is the set of chemical reactions that occur when the body is completely at rest. Consuming energy (calories) to maintain the basal metabolic rate is significant: it can represent more than two-thirds of our daily calorie consumption! Such consumption cannot be reduced since it is used to cover the minimal energy expenditures necessary to sustain the basic functions needed for our survival.

Thyroid gland

Located at the base of the neck, the thyroid gland secretes two hormones, thyroxine and triiodothyronine. Their main functions are as follows:

  • To activate basal metabolism and growth by stimulating the body's tissues to produce proteins
  • To increase the amount of oxygen the cells use

The thyroid gland's role in weight control

By controlling metabolism, the thyroid gland helps maintain body weight. When the thyroid gland is working too hard, a condition known as hyperthyroidism, the body burns many calories, leading to significant and sometimes unexplained weight loss. Accelerated basal metabolic rate is the main cause.

When it works below capacity, the body does not burn enough calories, which leads to weight gain. This is known as hypothyroidism and is usually accompanied by weight gain that is particularly difficult to lose because of the slower basal metabolic rate.

Our thyroid gland's health is one of the factors to consider when faced with unexplained weight gain or loss. That said, body weight is also affected by the interaction of several other factors, including the following:

  • Genetics
  • Age
  • Gender
  • Number of calories ingested
  • Number of calories burned by the basal metabolic rate
  • Amount of exercise

Is hyperthyroidism a good thing?

We might consider the ease of resting weight loss in those with hyperthyroidism to be quite positive. However, we would be forgetting that increased thyroid activity has its own set of disadvantages, including the following:

  • Increased risk of heart problems
  • Increased muscle contractions causing tremors
  • Increased sensitivity to heat
  • Affects bowel functioning and can cause more frequent stools

Whatever the cause, hyperthyroidism is definitely a reason to seek treatment. Likewise, taking high levels of thyroid hormone to lose weight is completely inappropriate and can be dangerous.

On the other hand, many hypothyroid patients (more than 10% of Canadians over 65) must also seek treatment for all the side effects of the disease other than weight gain, including the following:

  • Lack of energy and fatigue
  • Cold feet
  • Slow heart rate and shortness of breath
  • Irritability
  • Depression

Fortunately, the treatment is simple (one thyroxine tablet taken daily) and effective in most cases. [3]

What are the possible causes of thyroid dysfunction?

Several causes can throw the thyroid gland off balance and change the amount of hormone it secretes. They fall into the following three categories:

  1. Pituitary gland dysfunction: This problem may lead to hypo or hypersecretion of TSH (thyroid-stimulating hormone) or different factors of stimulation or inhibition of the thyroid.
  2. Thyroid gland problems: They may be due to inflammation or tissue destruction that is autoimmune (immune system dysfunction) or disease-related.
  3. Tissue resistance to hormonal activity: Although it is rare, sometimes tissues do not adequately absorb the hormones produced by the thyroid resulting in certain body disorders.

Are hormone treatments for weight loss effective?

With mild hypothyroidism, treatment with thyroid hormones, including thyroxine, will have minimal effect on body weight. Even with the most severe forms of hypothyroidism, weight loss from hormone treatment is not expected to exceed 10% of body weight. That is because the weight gain is only partly caused by the lack of thyroid hormone. Obesity is never caused solely by a hypofunctional thyroid gland.

Furthermore, thyroid hormones have little effect on fat accumulation in a particular tissue (abdomen, hips, buttocks, etc.). Other phenomena and hormones are involved in that process (insulin resistance, testosterone, estrogens, etc.). [4]

A prerequisite for weight loss

The web is full of advice on diet and exercise to help us lose weight, but normal thyroid function is a prerequisite for other methods to be effective. Fortunately, medical specialists have reliable tools, such as lab tests, to assess thyroid function and guide patients to appropriate treatments or lifestyle changes.

For professional support, we’re here for you.

We provide services that can help your doctor diagnose a thyroid gland dysfunction and related health problems and determine the appropriate treatment.

Do you have a medical prescription for this test? Book an appointment online or contact Biron Health Group’s customer service at 1 833 590-2712.

Sources4
  1. CHUM. (SD). Thyroid 101 (freely translated). https://www.chumontreal.qc.ca/patients/cicc/cancer-de-la-thyroide/thyroide-101#:~:text=La%20thyro%C3%AFde%20est%20la%20plus,la%20forme%20d%27un%20papillon.
  2. Hershman, Jerome M., October 2020. Merck Manual. Overview of the Thyroid Gland. https://www.merckmanuals.com/en-ca/home/hormonal-and-metabolic-disorders/thyroid-gland-disorders/overview-of-the-thyroid-gland
  3. Passeport santé. Hypothyroidism (freely translated). https://www.passeportsante.net/fr/Maux/Problemes/Fiche.aspx?doc=hypothyroidie_pm
  4. Portman, Luc and Giusti, Vittorio. “Obesity and hypothyroidism: Myth or reality?” (freely translated). Revue Médicale Suisse. https://www.revmed.ch/revue-medicale-suisse/2007/revue-medicale-suisse-105/obesite-et-hypothyroidie-mythe-ou-realite
Raymond Lepage, PhD, Doctor in Biochemistry
Raymond Lepage, PhD, Doctor in Biochemistry
Science popularizer
For about 50 years, Raymond Lepage worked as a clinical biochemist in charge of public and private laboratories. An associate clinical professor at the Faculty of Medicine of the Université de Montréal and an associate professor at the Université de Sherbrooke, he has also been a consultant, researcher, legal expert and conference speaker. He has authored or co-authored more than 100 publications for scientific conferences and journals, and now devotes part of his semi-retirement to popularizing science.