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The Impact of Obesity On Thyroid Health

Published January 13th 2014

Many people with thyroid and autoimmune thyroid conditions have problems losing weight. This frequently occurs with hypothyroidism and Hashimoto’s Thyroiditis, although occasionally someone with a hyperthyroid condition will also have difficulty losing weight. While a hypothyroid condition will slow down the metabolism, thus contributing to weight gain, there is evidence that obesity itself can affect thyroid function, and perhaps even trigger an autoimmune condition such as Graves’ Disease or Hashimoto’s Thyroiditis.

The reason why this is very important is because many people with thyroid and autoimmune thyroid conditions who are overweight think that the primary cause of this is the thyroid hormone imbalance. Although this might be the case with some people, in many people the opposite is true. And when this is the case, balancing the thyroid hormone levels isn’t the key to losing weight. The key is to address the inflammation associated with the obesity, which I’ll discuss in this article.

Differentiating Between Obesity and Being Overweight

Before I discuss this in greater detail I would like to briefly talk about obesity. Because the truth is, many men and women just think of themselves as being “overweight”, when the truth is that they are obese. While the terms “overweight” and “obese” both relate to the person’s weight being higher than what is considered to be healthy for the person, there of course is a difference between the two. Body mass index (BMI) is commonly used to determine if someone is overweight or obese. An adult who has a BMI between 25 and 29.9 is considered to be overweight, while an adult who has a BMI of 30 or higher is considered to be obese (1) [1]. Other methods of estimating body fat and body fat distribution include measurements of skinfold thickness and waist circumference, calculation of waist-to-hip circumference ratios, and techniques such as ultrasound, computed tomography, and magnetic resonance imaging (1) [1].

There are numerous factors which can lead to a person being overweight or obese. Obviously consuming too many calories and/or leading a sedentary lifestyle can cause or contribute to this. However, these two factors alone don’t always determine whether someone will be overweight or obese. After all, some people who don’t eat well and don’t exercise regularly aren’t overweight or obese, although sooner or later these bad habits will usually catch up with the person. Other factors which can lead to someone being overweight or obese include chronic stress, menopause, taking certain medications, and yes, having a hypothyroid condition.

Prevalence of Obesity

According to the World Health organization, worldwide obesity has nearly doubled since 1980 (2) [2]. Although they updated their fact sheet in March of 2013, their statistics are from 2008, as 1.4 billion adults were overweight, and of these over 500 million were obese (2) [2]. In addition, 35% of adults were overweight, and 11% were obese.

The Role of Leptin In Obesity

I have written a separate article entitled “The Role of Leptin In Thyroid Health [3]“. Leptin is a hormone released by white adipose tissue, mainly subcutaneous fat (3) [4]. However, other parts of the body such as the ovaries, skeletal muscles, stomach, and brown adipose tissue also secrete leptin (3) [4]. In lean individuals, leptin for the most part circulates in the bound form, whereas in obese individuals it circulates in the free form (4) [5]. Leptin regulates energy homeostasis, and its absence in rodents and humans causes severe obesity (5) [6]. What’s important for you to understand is that healthy levels of leptin in the body help to suppress appetite, which in turn is important to maintain a healthy weight.

As I discussed in the article I wrote about letpin and thyroid health, a deficiency of leptin will lead to an increase in appetite. However, most people who are obese actually have increased levels of leptin. The failure of elevated leptin levels to suppress feeding and mediate weight loss in common forms of obesity defines a state of so-called leptin resistance (6) [7]. So that you have a better understanding of this, let’s compare this to insulin resistance. Insulin is required to help decrease the blood sugar levels, but too much insulin can have the opposite effect, as eventually the body becomes resistant to the effects of insulin. Similarly, while the goal of leptin is to help to suppress appetite, too much leptin will lead to leptin resistance and have the opposite effect.

How Can Obesity Affect Thyroid Health?

Although an underactive thyroid can lead to weight gain, and even obesity in some cases, there is evidence that obesity itself can potentially lead to thyroid dysfunction. Even though treating hypothyroidism frequently results in weight loss, treatment involving thyroid hormone many times just results in modest weight loss (7) [8]. I commonly experience this with my patients who have Hashimoto’s Thyroiditis and take synthetic or natural thyroid hormone, as many times this will result in positive changes with the TSH, but for many of these people, taking thyroid hormone won’t have much of an impact on weight loss.

There is evidence that an increased TSH can be a consequence of obesity, since weight loss frequently will lead to a normalization of the TSH (8) [9]. Leptin seems to be a promising link between obesity and alterations of thyroid hormones since leptin concentrations influence TSH release (8) [9]. However, in some of these people with obesity, in addition to an elevated TSH, elevated free T3 levels were found to be positively associated with obesity (8) [9] (9) [10]. Free T4 was shown to be inversely correlated with obesity (9) [10]. The elevated TSH and low Free T4 levels make sense, but the elevated free T3 levels don’t make sense for someone with a hypothyroid condition. The cause of this isn’t known, although there are a few theories, such as an increased deiodinase activity in certain individuals with obesity which results in an increase in conversion of T4 to T3 (10) [9].

There is an enhanced secretion of some interleukins and inflammatory cytokines in adipose tissue of the obese as well as increased circulating levels of many cytokines (11) [11]. And as I have mentioned in past articles, inflammatory cytokines play a role in thyroid autoimmunity (12) [12] (13) [13]. Recent data have shown a relationship between obesity and thyroid autoimmunity, with the hormone leptin appearing to be the key factor (14) [14]. More research needs to be conducted in this area, but what’s important to understand is that both obesity and thyroid autoimmunity are inflammatory conditions, and it is possible that being obese might be one of the triggers of thyroid autoimmunity.

Is Obesity Linked To Thyroid Cancer?

Those who are obese might also have a greater risk of thyroid cancer. In fact, there is evidence that being overweight and obese is related to a modestly increased thyroid cancer risk (15) [15]. However, this is another area where more research is needed.

What Can Be Done To Overcome This Problem?

When someone with a thyroid or autoimmune thyroid condition is obese, in some cases it can be a challenge knowing whether the thyroid hormone imbalance is responsible for the increase in weight, or if the weight gain is what led to the development of a thyroid or autoimmune thyroid condition. In most cases it is assumed that the thyroid condition is what ultimately led to the weight gain. But frequently the person will take thyroid hormone, while at the same time clean up their diet and exercise regularly, yet still won’t notice a big difference when it comes to losing weight.

While eating well and exercising regularly are both very important, addressing the inflammatory component of the condition can be an essential component of correcting both the obesity problem, as well as suppressing the autoimmune response for someone dealing with an autoimmune thyroid condition. Eating an anti-inflammatory diet is of course important, but many times additional support is required in the form of omega 3 fatty acids, gamma-linolenic acid, making sure one’s vitamin D levels are over 50 ng/mL, etc. Sometimes additional support is necessary, and other natural agents which can help with the inflammation include turmeric, resveratrol, ginger, and bromelain. However, it’s important to understand that in order to eliminate the inflammation you must remove the factor or factors which are causing the inflammation. In other words, giving anti-inflammatory nutrients won’t be too effective if you don’t remove the inflammatory trigger.

In summary, weight gain and obesity are common with thyroid and autoimmune thyroid conditions. And while it is often assumed that an imbalance in thyroid hormone (usually a hypothyroid condition) is responsible for the increase in weight, sometimes the weight gain is what leads to the development of a thyroid or autoimmune thyroid condition. The problem is that many people think of obesity as being a “static” condition. In other words, most people don’t realize that an increase in adipose tissue will result in inflammation, and in some cases this inflammation can be severe enough to trigger an autoimmune response. As a result, many times balancing the thyroid hormone levels alone isn’t sufficient to address obesity, as other factors need to be considered in order to correct the inflammatory process, which in turn can help greatly with weight loss.