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How a Low Functioning Thyroid Can Lead to Weight Gain After 50

By Julie Dargan March 21, 2021 Health and Fitness

In a previous article I discussed the effects of estrogen on your body and subsequent weight gain. Then I followed with a discussion on cortisol, also known as the stress hormone.

This week I am going to assess how having a low functioning thyroid could be adding to your weight gain woes, even if all your blood levels come back normal.

Thyroid and Weight Gain

Weight gain can be directly linked with thyroid problems. Thyroid issues develop over time. You may have been displaying signs of low thyroid function in your 30s or 40s but were able to push through it.

Back then you were able to exercise a little more to lose any extra weight, or sleep in over the weekends to make up for any tiredness. You probably did not give these changes a second thought.

As you enter your late 40s, these symptoms tend to become more apparent because of any hormonal fluctuations that are also experienced during that time. You need to listen to your thyroid and the signs your body is receiving, and nurture your thyroid if you want to lose weight and gain energy.

Weight gain is typically linked to an under active thyroid because it slows down your metabolism. This results in weight gain and difficulty losing extra weight.

An under active thyroid gland, a condition referred to as hypothyroidism, is where your thyroid gland doesn’t produce enough hormones. Common signs of an under active thyroid are tiredness, weight gain and feeling depressed.

Weight Gain and Hormone Shifts

Women’s weight tends to fluctuate, especially when hormone levels are shifting, which happens as you approach menopause. Many women try to diet to counter this with unhealthy eating plans or a plan that does not address their thyroid, only to make things worse.

Eating the wrong foods can decrease your gut mobility, which slows down your metabolism and causes you to gain more weight. Then, when you find that you do not get the weight loss you were expecting, you revert back to your old eating habits.

Low thyroid function is associated with weight gain due to the fact that the thyroid gland controls fuel-efficiency and your metabolism. With too little thyroid, the fuel (your food) is burned at a lower rate. If meal sizes are the same, weight gain occurs.

Tiredness associated with low thyroid function also can find you too tired to exercise as much as you would like to, further adding to weight gain.

A note of caution: Although weight gain often occurs with hypothyroidism, it is a nonspecific change because increasing weight also occurs with decreased exercise, stress and as a side effect of many drugs.

So do not be quick to assume that you have an under active thyroid if you have gained weight or are unable to lose weight.

Causes of Low Thyroid Function

Estrogen dominance can decrease your thyroid activity by inhibiting the release of thyroid stimulating hormone (TSH). TSH is a hormone secreted by your pituitary gland when your thyroid hormone levels are low. Low thyroid function can also cause progesterone levels to decrease.


An under active thyroid, referred to as hypothyroidism, can present with symptoms that are usually mild and nonspecific. Therefore, it can be easy to dismiss them at the start as not being particularly important. But this is an issue that needs to be addressed.

Hypothyroidism stems from a problem with the thyroid gland, which reduces the amount of the hormone thyroxine it produces.

An under active thyroid can lead to fatigue, brain fog, weight gain, depression, constantly feeling cold and even hair loss. All of these can also be experienced during perimenopause and menopause. A common cause of hypothyroidism is Hashimoto’s disease.

Sub-Clinical Hypothyroidism

You do not have to have a disease of the thyroid to feel the effects of low thyroid function.

Many of my clients would be in tears with the tiredness and exhaustion they experience, yet blood tests come back normal, making them feel that they are going crazy. It certainly does not help when their doctor will not listen to what they are feeling and will only respond to blood tests.

What could be happening is a condition referred to as sub-clinical hypothyroidism where your thyroid is not working to its full potential but blood tests are coming back within normal ranges.

All your blood tests may come back normal but you are most certainly experiencing nearly every symptom associated with low thyroid function. Even low thyroid function can lead to weight gain, especially when it is interconnected with other hormonal issues.

If your thyroid is not functioning as well as it should be, all of your efforts to curb weight gain and achieve hormone harmony may be futile.

Hypothyroidism can occur at any stage in life but it most commonly occurs in women between the ages of 40 and 50. At this age, some women mistake their symptoms are just a part of the menopause or getting older.

Both perimenopause and hypothyroidism commonly occur in midlife women. Perimenopause is a phase that happens for all women and the incidence of hypothyroidism increases with increasing age, especially in women. Therefore, perimenopause and new onset hypothyroidism may occur together.

Here are top 5 tips to improve your thyroid function and help curb the battle of the belly fat.

Decrease the Amount of Processed Foods

A diet high in processed foods can cause inflammation in the body. It also inhibits the thyroid hormone conversion of T4 to T3, T3 being the active form that the body uses.

Gluten and the Thyroid

There is a strong connection between gluten reactions and the thyroid. Some people will be able to completely put their conditions into remission by going gluten-free, while others may need to dig a bit deeper. Eliminating gluten from your diet for 1-3 weeks can be of great benefit.

Selenium and Zinc

Two nutrients directly involved in thyroid function are selenium and zinc. Consuming a diet naturally rich in selenium and zinc is critical for maintaining a healthy thyroid and metabolism. These foods include brazil nuts, tuna, sardines, eggs and pumpkin seeds.

Vitamin D

Get more Vitamin D into your body. This fat soluble vitamin is necessary for thyroid hormone production in the pituitary gland. So be sure to get out and bare your arms and legs at least 20 minutes a day, without UV protection to absorb essential Vitamin D.

Depend on Greens

Add a green smoothie to your diet. This is one of the best ways to make sure you are getting enough nutrients into your day. It is easy to make, easy to digest and packed full of vitamins and minerals that your body needs.

Do you think your thyroid is sluggish? Have you had any blood tests to ascertain if your thyroid function is low only to be told everything is fine? I would love to know what experience you have had. Let me know in the comments below.

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The Author

Julie Dargan (RN, ND, BHSc) has experience assisting women going through hormonal changes and want to live each day with confidence and enthusiasm.

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