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Why Is It So Hard to Lose Weight When You’re Hypothyroid?

When you’re hypothyroid, it can seem nearly impossible to lose weight. Find out why it’s so hard, along with resources to achieve a healthy
Why Is It So Hard to Lose Weight When You’re Hypothyroid?
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For many people with hypothyroidism, it can be difficult – and feel utterly impossible – to lose or stop gaining weight. This challenge can continue even after hypothyroidism treatment. What’s really going on? Ahead, a look at the factors that make maintaining a healthy weight so hard for many people with an underactive thyroid gland and some of the steps you can take towards achieving your weight goals.

The metabolic slowdown

When you’re hypothyroid, your thyroid gland isn’t producing enough thyroid hormones, namely thyroxine (T4) and triiodothyronine (T3). These hormones are responsible for regulating your metabolism. When these key thyroid hormone levels are low, your metabolism – the body’s ability to effectively use energy and oxygen --  slows down. This metabolic slowdown can lead to fatigue, weight gain, and other metabolic changes that make it harder to maintain a healthy weight.

Hypothyroidism makes it harder to achieve a healthy weight because of the impact of an underactive thyroid on your Basal Metabolic Rate, also known as the BMR.

BMR is defined as the rate of energy your body spends during a minute, hour, or day to maintain basic body functions such as breathing, pumping blood, maintaining body temperature, and primary brain function. It is the body’s metabolic rate at rest, accounting for up to 75% of all energy spent throughout the day.

BMR is usually expressed in calories. You’ve undoubtedly seen charts that show the average BMR – or calories required at rest -- for people of a certain height/weight, age, and biological sex. These charts are based on a generally healthy population.

In a healthy person, BMR is impacted by the following:

  • Body size and composition: If you are taller or heavier, your BMR will be higher. If you have more muscle than fat mass, your BMR will be higher.
  • Biological sex: On average, females have 10% lower BMR than males.
  • Age: After the age of 30, increasing age lowers BMR.
  • Where you live: If you live in a tropical or cold climate, your body will spend extra energy to keep your body temperature at its level.
  • Inflammation: Inflammation from fever or injury can increase BMR.
  • Thyroid hormone levels: Lower levels of thyroid hormones can slow down the BMR.

Extensive research shows that thyroid hormone is an important determinant of overall energy expenditure, and low thyroid hormone levels can reduce BMR.

After we eat and digestion starts, deiodinases -- enzymes whose function is to convert T4 to T3 – activate. A similar process happens in the muscles after exercise. Deiodinases help convert T4 into T3, and T3 helps with muscle growth and maintenance.

Thyroid hormones activate energy-producing processes in our cells’ mitochondria, the cell’s powerhouse. There, nutrients are broken down, creating energy for the cells.

This process is impaired when we don’t have enough thyroid hormone. As a result, BMR is reduced.

You might think treating hypothyroidism restores BMR to normal, but that is not the case. Research shows that even with thyroid hormone replacement treatment, the metabolism often remains from 10 to 20% less efficient, making it harder to maintain a healthy weight.

Let’s look at an example of how a hypothyroidism-impaired BMR can affect weight. Taking the example of a healthy woman who is 5’6”, weighs 150 pounds, and is 40 years old, the standard BMR formula would calculate her BMR at 1350 calories. This woman would burn around 1350 calories per day if she were at rest and did not engage in any physical activity.

Now, let’s say that another woman of the same age, height, and weight has a BMR that’s 20% reduced due to her hypothyroidism. She would have a BMR of 1080 calories, a significant difference of more than 300 calories daily!

Using the most basic weight loss formula – to gain 1 pound of fat, you need to eat 3,500 more calories than you burn --  you can see that our hypothetical woman with hypothyroidism is at a significant disadvantage. If both women remained entirely at rest and each consumed 1350 calories a day, the healthy woman would maintain the same weight of 150 pounds. The hypothyroid woman, however, could gain 1 pound every 11.5 days. That translates to a weight gain of 33 pounds in 1 year!

Increased risk of insulin resistance

Thyroid hormones have a significant effect on how your body processes sugar (glucose) and on the way that insulin functions in the body.  

Insulin is a hormone that helps your body regulate blood sugar levels. When you eat, food is converted into glucose. The pancreas then releases insulin, which helps your body process the glucose either for immediate use or storage.

Insulin resistance is a condition where cells in the muscles, fat, and liver don’t respond well to insulin and cannot easily take up glucose from the blood. As a result, the pancreas produces more insulin to compensate, leading to high blood sugar levels over time.

Insulin resistance can be caused by factors such as excess body fat, physical inactivity, and a family history of type diabetes.

The signs of insulin resistance may include a waistline over 40 inches in men and 35 inches in women and high blood pressure and cholesterol levels.

Studies have shown that hypothyroidism is a significant risk factor for insulin resistance. And insulin resistance is linked to weight gain – and difficulty losing weight -- because the body stores excess blood sugar as fat.

According to a recent study, insulin resistance can prevent weight loss despite dieting and exercising. Research has shown that insulin resistance makes it harder to lose weight, and when weight is lost, a lower percentage of that loss is fat. Another complication is that the more weight that’s gained, the harder it becomes to lose.

Increased risk of leptin resistance

Leptin is a hormone that regulates hunger levels and gives you the feeling of fullness. When you eat, leptin is released, sending a message to the brain that you are satiated. Sometimes, however, the brain doesn’t respond to leptin normally. This condition, known as leptin resistance, can cause you to eat more, even though your body has enough fat stores to meet your energy needs.

Leptin resistance is believed to be a leading driver of fat gain and may be one of the main reasons people gain weight and have a hard time losing it.

Hypothyroidism is one of the most common medical conditions associated with leptin resistance. Specifically, leptin resistance can be caused by a decrease in thyroid hormones. When these hormones are out of balance, it makes it harder for your body to use leptin correctly and can lead to weight gain.

Another potential cause of leptin resistance is chronic inflammation. This could be caused by a poor diet that’s high in sugar, processed foods, and unhealthy fats. High levels of inflammation can reduce the sensitivity of your cells to leptin, making it harder for your body to process information from the hormone.

Finally, leptin resistance can also be caused by chronic stress. When you’re stressed, your body produces hormones like cortisol and epinephrine that can make it harder for leptin to do its job in regulating appetite and energy levels.

Problems that effect wieght loss when you have hypothyroidism

Reduced fat-burning

Thyroid hormones play a direct role in stimulating fat burning from fat stores – known as lipolysis -- and from dietary fat sources. Lipolysis is the metabolic process through which lipids or fats are broken down. This process occurs mainly in fatty tissues and is used to mobilize stored energy when it’s needed. Hormones, including insulin, regulate the process. The higher the circulating insulin levels, the less fat-burning takes place.

Hypothyroidism reduces lipolysis and makes it harder for your body to burn fat.

Increased hunger

In some people with hypothyroidism, an underactive thyroid can cause an increase in appetite. The sensation of hunger can be partly due to impaired absorption of nutrients but may also be related to fatigue. Some people find that they tend to eat more when they have ongoing exhaustion, especially fast-converting carbohydrates and sugar.

Water retention

Another challenge associated with weight loss in hypothyroidism is water retention. When you’re hypothyroid, adrenal hormones are often not secreted properly, resulting in low sodium levels and blood pressure, which causes water retention. Another reason is that a lower body temperature, characteristic of hypothyroidism, can cause fluid accumulation in various parts of the body.

This excess water weight can cause bloating and puffiness and may mask any progress made on the scale.

Lack of energy and exercise limitations

Individuals with hypothyroidism often experience fatigue and low energy levels due to their condition. This can make it difficult to get regular physical activity, which is an important component of weight loss. Additionally, hypothyroidism can cause joint pain and muscle weakness, making engaging in physical activity even more challenging.

How to lose weight with Hashimoto’s and hypothyroidism

Losing weight with hypothyroidism and/or Hashimoto’s can be difficult, but it is possible. The key is approaching the challenge from multiple directions, building on a foundation of optimal thyroid treatment with the right thyroid hormone replacement medication. Your plan needs to include dietary changes, supplements, physical activity, sleep, stress management, and potentially the addition of prescription medications.

Optimal thyroid treatment

Paloma patients frequently report feeling best – and are better able to lose weight – when their TSH levels are less than 2.0 and Free T4 and Free T3 levels are in the upper half of the reference range. If your TSH levels are high and Free T4 and Free T3 levels are low, subclinical hypothyroidism can make weight loss an uphill battle. The key is optimizing your thyroid function so that you’re taking the right thyroid hormone replacement drug at the right dose to relieve symptoms and improve your metabolism safely.

Remember that after starting thyroid treatment or increasing your dose of thyroid medication, it takes time to help boost your metabolism. Even then, thyroid treatment is not a magic weight loss cure, and changes to your diet and activity level will still be necessary to achieve the goal of weight loss and healthy weight management.

Dietary changes

There is no one perfect diet for weight loss when you’re hypothyroid. For example, if you have Hashimoto’s, the autoimmune disease that causes hypothyroidism, you may find the Autoimmune Protocol (AIP) Diet most effective because it focuses on reducing inflammation.

If you have insulin resistance and high blood sugar, you may find a low-carbohydrate Ketogenic Diet, the Paleo Diet, and Intermittent Fasting approaches helpful in improving your health and metabolism for successful weight loss.

Whatever approach you take to diet, there’s one crucial thing to remember: don’t starve yourself. By eating an extremely low-calorie diet, or crash dieting, you push your body into starvation mode. As a result, the body will try to conserve as much energy as possible, because the body doesn’t know when it will get enough food again. By entering starvation mode your metabolism slows, and your body actually needs fewer calories than in a non-starvation mode.

Here’s another tip to help with weight loss and metabolism: limit alcohol consumption. Alcohol can directly block thyroid function, interfere with the production of both free T4 and free T3 and increase levels of Reverse T3. Reverse T3 is biologically inactive and prevents active T3 from reaching the cells. When Reverse T3 is elevated, this can lower your BMR.


In addition to changes to your diet, supplements can help support your thyroid and weight loss.

Many Paloma patients take Paloma’s Daily Thyroid Care supplement, which provides nutritional support for optimal thyroid function. A number of key supplements are also recommended for thyroid patients to bolster thyroid function.

Several supplements specifically focused on weight loss may also be helpful in your plan. These include Berberine and Myo-Inositol.

Physical activity

Physical activity is a necessary part of your weight loss plan. For an in-depth look at exercise and activity, view our video on “How To Exercise Safely & Effectively With Hashimoto’s Disease,” featuring several experts offering advice.

Something to keep in mind about physical activity: don’t overexercise! When you overexercise or regularly engage in high-intensity exercise, you risk using up all the available free T3 in your body. As a consequence, you won’t have enough T3 – the active thyroid hormone -- to power your metabolism to process the food you’ve eaten effectively. It’s best to focus on incorporating medium-intensity activity and muscle-building into your daily routine. You’ll increase your BMR and burn more calories throughout the day.

Get enough sleep

Aim for 7 to 9 hours of sleep per night for successful weight loss. When you don’t get enough sleep, your body produces more hunger and appetite hormones, and less leptin, which helps you feel full. This can lead to overeating and weight gain. Additionally, sleep deprivation can cause metabolic changes, including glucose intolerance and insulin resistance, which can contribute to weight gain and obesity.

Stress management

You should also incorporate a daily stress management practice to help balance hormones and promote weight loss. Stress can increase appetite and cause cravings for sweet, fatty, and salty carbohydrate-rich foods, leading to overeating and weight gain. Stress can also increase levels of the adrenal hormone cortisol, which stimulates fat and carbohydrate metabolism and increases appetite. Elevated cortisol levels can also cause higher insulin levels, leading to rapid drops in blood sugar that trigger cravings for sugary, fatty foods.

Chronic stress also encourages fat storage, particularly around the belly!

Prescription drugs

You may also want to discuss with your practitioner whether prescription treatments could be part of your weight loss journey. Paloma has several articles to help you explore the possible medications to consider. These include:

  • Topamax – an anticonvulsant medication that is prescribed off-label to aid in weight loss
  • Metformin (Glucophage) – a type 2 diabetes drug
  • Wellbutrin – an antidepressant that is sometimes prescribed to aid in weight loss
  • Semaglutide (Ozempic) – a once-weekly injectible type 2 diabetes drug
  • Phentermine – the “Phen” of the famed “Fen-Phen” weight loss drug combination popular in the past
  • Low Dose Naltrexone (LDN)  - a medication that’s prescribed off-label to reduce inflammation and aid in weight loss

A note from Paloma

An important note regarding weight loss success: If you lose 10% or more of your weight, be sure to have your thyroid levels rechecked because you may need a lower thyroid medication dose. The one temporary downside of weight loss is the risk of overdosing on thyroid medication. So, be alert to any signs and symptoms of hyperthyroidism, such as excessive sweating, a rapid or irregular heartbeat, insomnia or difficulty sleeping, anxiety, and diarrhea.

To stay on top of your thyroid levels, try Paloma’s convenient at-home thyroid test kit. This affordable panel measures TSH, Free T4, Free T3, and Thyroid Peroxidase Antibodies (TPOAb). You can also add on a Reverse T3 and Vitamin D test.

Most importantly, healthy weight loss and weight management for people with hypothyroidism require optimal treatment of your thyroid condition. For the best results, consider working with one of Paloma Health’s top thyroid practitioners to help you understand your test results and oversee your personalized – and effective – treatment plan for an underactive thyroid. Convenient virtual visits with thyroid doctors are available from the comfort of your home.

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Vedrana Högqvist Tabor, Ph.D., contributed to this article.


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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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