Table of ContentsView AllTable of ContentsMetabolismThyroid HormonesHypothyroidismHyperthyroidismWeight Loss
Table of ContentsView All
View All
Table of Contents
Metabolism
Thyroid Hormones
Hypothyroidism
Hyperthyroidism
Weight Loss
Though scientists do know that thyroid hormones regulate your body’s metabolism, the exact relationship between thyroid hormones, metabolism, and weight changes is a complex one that isn’t well understood.
When your thyroid isn’t producing enough hormones (hypothyroidism), your metabolism slows down. This reduces the number of calories your body burns and often leads to weight gain.
Conversely, when your thyroid is producing too many hormones (hyperthyroidism), your metabolism goes into overdrive, burning more calories than normal and likely resulting in weight loss.
However, this is a simplistic picture of the various factors that are involved in these processes.
1:33How the Thyroid Gland Works
1:33
How the Thyroid Gland Works
The Role of Metabolism
How to Boost Metabolism: 12 Evidence-Based Ways
The Role of Thyroid Hormones
Thyroid hormones heavily influence your metabolism, your body temperature, and your appetite regulation. Your thyroid works closely with your hypothalamus, a small area of your brain, to maintain both your weight and your energy balance—what’s left after you eat and your body uses the calories it needs.
How this happens isn’t exactly clear, but one thing is certain: It isn’t thyroid hormones alone that play a role in how much energy your body uses. Thyroid hormones work along with a number of other hormones, proteins, nuclear receptors, and chemicals, which is why it’s such a complicated process.
Research
Various studies on the relationship between thyroidhormones and weight gainhave returned different conclusions. Most often, studies have shown that in the obese population, the following is true regarding thyroid hormones:
However, some studies have reported these hormone levels to be normal or even decreased.
For instance, a 2014 study looked at a community-based sample of 1,944 adults with normal thyroid function who were followed for 11 years. The researchers found that TSH levels increased as weight increased over time in both males and females.
The study concluded that the association between TSH and weight gain doesn’t necessarily mean that one causes the other. Instead, the researchers proposed that there could be a third factor involved.
But a 2017 study examined 1,100 participants with normal thyroid function and found no link between changes in TSH andbody mass index (BMI)after a follow-up period of 10 years. This study did find, however, that patients with lower levels of free T4 tended to have higher BMIs.
The variance in study results further illustrates how intricate the relationship between thyroid hormones and weight really is. The bottom line is that further research is needed.
BMI is a dated, flawed measure. It does not take into account factors such asbody composition,ethnicity, sex, race, and age. Even though it is a biased measure, BMI is still widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.
21 Reasons You’re Not Losing Weight—and How to Address Them
Hypothyroidism and Weight
As discussed above, the simplistic explanation is that having an underactive thyroid often causes people to gain weight because their bodies stop using calories efficiently. A lot of this weight is excess water and salt. Typically, the more severe thehypothyroidism, the greater the weight gain, but usually it’s between 5 and 10 pounds.
Somewhere between 10% and 60% adults with obesity also have autoimmune hypothyroidism.Some studies have concluded that even mild hypothyroidism can lead to weight gain and changes in one’s BMI.
Emily Roberts / Verywell
Weight Loss With Treatment
There aren’t many scientific studies regarding how much weight is gained or lost once hypothyroid people are treated with the synthetic thyroid hormone levothyroxine, but the limited evidence that is available indicates that not everyone loses weight with treatment and in the ones who do, it’s limited.
Once your hormone levels are within the normal range, you may lose a small amount of weight that mainly consists of the extra water and salt your body has built up. However, weight gain has multiple factors, and yours is more than likely not all due to your thyroid’s slowdown. One way to tell is if treatment has helped all of your other thyroid symptoms, but not your weight. This indicates that your thyroid very likely isn’t the only factor behind your gain.
The More Medication Myth
You may have heard that thyroid hormones can beused to lose weight, even in people without thyroid disease. While synthetic thyroid hormones have been used this way in the past, research has shown that most people gain all the weight back once they stop using them.Worse, being on thyroid hormones unnecessarily can result in serious side effects.
For people who are already using levothyroxine, increasing the dose above what’s needed can lead to more weight loss, but it’s usually not significant and those pounds are often gained back once the dose is decreased again.
This is also an unhealthy way to lose weight, as an increased dose is also associated with adverse reactions, including heart issues, insomnia, headaches, menstrual irregularities, and skin rash.
Are You Taking Too Much Levothyroxine?
Hyperthyroidism and Weight
Many patients with an overactive thyroid end up losing weight. And in general, the more severe the hyperthyroidism, the more weight that is lost. But because metabolisms in these individuals are working harder and faster, they often feel hungrier and some may gain weight instead.
This usually reverses once your hyperthyroidism is treated. You may find that you gain back all the weight you lost, which is totally normal. If you eventually end up in a hypothyroid state, as many hyperthyroid patients do after thyroid surgery or radioactive iodine therapy, you may also run into the challenges of maintaining or losing weight.
The Weight Loss Challenge
Losing weight can be a challenge when you’re dealing with hypothyroidism. Researchers aren’t exactly sure why this is, but low T3 levels and hormone resistance issues may play a role.
In some cases, knowing how much to eat and discussing the best foods with a dietitian or nutrition professional can be a helpful first step.
Low T3 Levels
T3 is the active thyroid hormone at the cellular level, delivering oxygen and energy to cells, and it’s often low in hypothyroid patients. Lower T3 levels are associated with lower resting metabolic rates.
As mentioned previously, when your metabolism is lower, you need both lower calorie intake and more activity to burn calories in order to maintain your current body weight or lose weight. This can make losing weight extremely difficult.
Hormone Resistance
Another contributing factor to the weight loss challenge may be that hormone resistance problems often occur in people with thyroid disease, includingleptin resistanceand insulin resistance.
Leptin Resistance
When there’s too much leptin, which also happens when you’re obese, your body becomes less sensitive to leptin’s signals, resulting in leptin resistance.This means that your hypothalamus isn’t being properly told that you’re satisfied, so it goes into starvation mode, decreasing the number of calories you’re burning and telling you that you’re still hungry.
In the meantime, your thyroid slows down your metabolism as your appetite increases, you eat more, and you burn fewer and fewer calories, all resulting in weight gain. And the more pounds you put on, the more leptin your fat cells make, further enabling this cycle.
Insulin Resistance
As in leptin resistance, when your insulin levels are continually elevated, your cells become less sensitive to the signals insulin gives. This results in needing even more insulin to keep your blood sugar level steady. Having higher levels of insulin causes weight gain and raises your risk of developing type 2 diabetes.
Insulin is considered a fat-building hormone—it increases the amount of fat around the abdominal organs, which is highly inflammatory and can raise your risk of chronic diseases like type 2 diabetes. Studies show that both hyperthyroidism and hypothyroidism can create insulin resistance.
Insulin Resistance: How to Test and Manage Symptoms
A Word From Verywell
Thanks to the complexities involved with hormones and metabolism, the reality is that if you have an underactive thyroid, you may have to work harder to lose weight than someone without a thyroid disorder.
If you’re continually hitting roadblocks, talk to your healthcare provider about optimal treatment. Once your treatment is optimized—which means that your thyroid levels are in the optimal range foryou, not just in the normal reference range—you may find that it’s easier to lose weight.
According to the American Thyroid Association, when your thyroid hormone levels are normalized, you should be able to lose, maintain, and gain weight just like someone without thyroid disease.It may also help to increase your protein intake, get your glucose and leptin levels checked, adhere to a healthier diet, and strengthen your muscles to boost your ability to lose those extra pounds.
Above all, don’t give up! Hard work and determination can get you where you want to go.
Is It Possible to Lose Weight With Hypothyroidism?
9 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kouidhi S, Clerget-Froidevaux MS.Integrating thyroid hormone signaling in hypothalamic control of metabolism: crosstalk between nuclear receptors.Int J Mol Sci. 2018;19(7). doi:10.3390/ijms19072017Sanyal D, Raychaudhuri M.Hypothyroidism and obesity: an intriguing link.Indian J Endocrinol Metab. 2016;20(4):554-557. doi:10.4103/2230-8210.183454Bjergved L, Jørgensen T, Perrild H, et al.Thyroid function and body weight: a community-based longitudinal study.PLOS ONE. 2014;9(4):e93515. doi:10.1371/journal.pone.0093515Abdi H, Kazemian E, Gharibzadeh S, et al.Association between thyroid function and body mass index: a 10-year follow-up.Ann Nutr Metab. 2017;70(4):338-345. doi:10.1159/000477497American Thyroid Association.Thyroid & weight.Food and Drug Administration.LEVO-T®: highlights of prescribing information.Gruzdeva O, Borodkina D, Uchasova E, Dyleva Y, Barbarash O.Leptin resistance: underlying mechanisms and diagnosis.Diabetes Metab Syndr Obes. 2019;12:191-198. doi:10.2147/DMSO.S182406Iwen KA, Schröder E, Brabant G.Thyroid hormones and the metabolic syndrome.Eur Thyroid J. 2013;2(2):83-92. doi:10.1159/000351249American Thyroid Association.Thyroid and weight FAQs.
9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kouidhi S, Clerget-Froidevaux MS.Integrating thyroid hormone signaling in hypothalamic control of metabolism: crosstalk between nuclear receptors.Int J Mol Sci. 2018;19(7). doi:10.3390/ijms19072017Sanyal D, Raychaudhuri M.Hypothyroidism and obesity: an intriguing link.Indian J Endocrinol Metab. 2016;20(4):554-557. doi:10.4103/2230-8210.183454Bjergved L, Jørgensen T, Perrild H, et al.Thyroid function and body weight: a community-based longitudinal study.PLOS ONE. 2014;9(4):e93515. doi:10.1371/journal.pone.0093515Abdi H, Kazemian E, Gharibzadeh S, et al.Association between thyroid function and body mass index: a 10-year follow-up.Ann Nutr Metab. 2017;70(4):338-345. doi:10.1159/000477497American Thyroid Association.Thyroid & weight.Food and Drug Administration.LEVO-T®: highlights of prescribing information.Gruzdeva O, Borodkina D, Uchasova E, Dyleva Y, Barbarash O.Leptin resistance: underlying mechanisms and diagnosis.Diabetes Metab Syndr Obes. 2019;12:191-198. doi:10.2147/DMSO.S182406Iwen KA, Schröder E, Brabant G.Thyroid hormones and the metabolic syndrome.Eur Thyroid J. 2013;2(2):83-92. doi:10.1159/000351249American Thyroid Association.Thyroid and weight FAQs.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Kouidhi S, Clerget-Froidevaux MS.Integrating thyroid hormone signaling in hypothalamic control of metabolism: crosstalk between nuclear receptors.Int J Mol Sci. 2018;19(7). doi:10.3390/ijms19072017Sanyal D, Raychaudhuri M.Hypothyroidism and obesity: an intriguing link.Indian J Endocrinol Metab. 2016;20(4):554-557. doi:10.4103/2230-8210.183454Bjergved L, Jørgensen T, Perrild H, et al.Thyroid function and body weight: a community-based longitudinal study.PLOS ONE. 2014;9(4):e93515. doi:10.1371/journal.pone.0093515Abdi H, Kazemian E, Gharibzadeh S, et al.Association between thyroid function and body mass index: a 10-year follow-up.Ann Nutr Metab. 2017;70(4):338-345. doi:10.1159/000477497American Thyroid Association.Thyroid & weight.Food and Drug Administration.LEVO-T®: highlights of prescribing information.Gruzdeva O, Borodkina D, Uchasova E, Dyleva Y, Barbarash O.Leptin resistance: underlying mechanisms and diagnosis.Diabetes Metab Syndr Obes. 2019;12:191-198. doi:10.2147/DMSO.S182406Iwen KA, Schröder E, Brabant G.Thyroid hormones and the metabolic syndrome.Eur Thyroid J. 2013;2(2):83-92. doi:10.1159/000351249American Thyroid Association.Thyroid and weight FAQs.
Kouidhi S, Clerget-Froidevaux MS.Integrating thyroid hormone signaling in hypothalamic control of metabolism: crosstalk between nuclear receptors.Int J Mol Sci. 2018;19(7). doi:10.3390/ijms19072017
Sanyal D, Raychaudhuri M.Hypothyroidism and obesity: an intriguing link.Indian J Endocrinol Metab. 2016;20(4):554-557. doi:10.4103/2230-8210.183454
Bjergved L, Jørgensen T, Perrild H, et al.Thyroid function and body weight: a community-based longitudinal study.PLOS ONE. 2014;9(4):e93515. doi:10.1371/journal.pone.0093515
Abdi H, Kazemian E, Gharibzadeh S, et al.Association between thyroid function and body mass index: a 10-year follow-up.Ann Nutr Metab. 2017;70(4):338-345. doi:10.1159/000477497
American Thyroid Association.Thyroid & weight.
Food and Drug Administration.LEVO-T®: highlights of prescribing information.
Gruzdeva O, Borodkina D, Uchasova E, Dyleva Y, Barbarash O.Leptin resistance: underlying mechanisms and diagnosis.Diabetes Metab Syndr Obes. 2019;12:191-198. doi:10.2147/DMSO.S182406
Iwen KA, Schröder E, Brabant G.Thyroid hormones and the metabolic syndrome.Eur Thyroid J. 2013;2(2):83-92. doi:10.1159/000351249
American Thyroid Association.Thyroid and weight FAQs.
Meet Our Medical Expert Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?OtherHelpfulReport an ErrorSubmit
What is your feedback?
