Losing weight can be a real struggle when you have thyroid disease, even with a healthy diet and exercise. Multiple changes in your body are believed to be behind this problem.

It can be discouraging when you work hard to lose weight and don’t see a change on the scale. The good news is that the proper treatments and strategies may help with weight loss.

This article discusses why it’s so hard to lose weight with hypothyroidism (low thyroid activity) and the role of hormones. It also covers treatments to consider, plus how to effectively eat and exercise.

The Thyroid Weight-Loss Problem

According to researchers, even slight shifts in thyroid function are linked to weight gain. They don’t fully understand why an underactive thyroid causes weight gain or prevents weight loss. They suspect it’s due to:​

  • A slower metabolism
  • Less energy, which leads to less activity
  • Changes in how your body processes, stores, and burns off fat and glucose (sugar)
  • A tendency to retain fluids in tissues

Much of the weight gain associated with hypothyroidism is due to salt and fluids, not body fat.

Weight Loss and Thyroid Hormones

Three important hormones are related to thyroid function:

  • Thyroid-stimulating hormone (TSH)Triiodothyronine (T3)Thyroxine (T4)

T3 and T4 are produced by the thyroid gland. TSH is made by the pituitary gland when your body detects low levels of T3 and/or T4. Its job is to stimulate the thyroid to make more of those hormones.

T3 and T4 regulate your:

  • MetabolismHeart rateDigestive functionMuscle controlBone maintenanceBrain development

Typically, hypothyroidism is diagnosed and monitored with TSH tests and treated with only replacement T4 hormone (levothyroxine).

Untreated or Undertreated Hypothyroidism

You may find it difficult—or even impossible—to lose weight if your hypothyroidism is untreated or undertreated. If you’ve tried diet and exercise without success, consider having your thyroid hormone levels tested.

High TSH, Low Thyroid Function

Because TSH is made in response to low thyroid hormone levels, a high level of TSH suggests low levels of thyroid hormones.

  • If you’re already being treated for hypothyroidism, your thyroid hormone levels may not be in the optimal range. You may need a dosage increase or additional medications.If you haven’t been diagnosed with thyroid disease but can’t lose weight, testing may reveal hypothyroidism.

It’s possible to have weight loss problems when thyroid hormone tests show you’re in the correct range for thyroid-stimulating hormone (TSH). That’s not the only measure of thyroid function, and research suggests there’s no TSH level that’s optimal for everyone with hypothyroidism.

So, even if your tests come back “normal,” you may need a medication adjustment. Often, it’s a low T3 level that blocks weight loss efforts.

You can ask a healthcare provider to test your free T3 level. If it’s low, they may add the T3 replacement hormone liothyronine to your treatment regimen. For weight loss, studies show this is a more effective approach than levothyroxine alone.

The Role of Other Hormones

Some people with thyroid disease have other hormonal imbalances that can get in the way of successful weight loss. These include:

  • Leptin and ghrelin are hormones that regulate weight and appetite. Low levels contribute to obesity and an inability to lose weight.
  • Insulin deals with glucose usage and fat storage. In insulin resistance, your body doesn’t use insulin efficiently and therefore needs more, which leads to additional fat stores.
  • High levels of the stress hormone cortisol can lead to overeating and weight gain.

You may want to ask for tests of these hormones if your weight-loss efforts are unsuccessful.

Key Components of Weight Loss

Whatever diet or exercise plan you follow, don’t neglect these basic necessities for weight loss:

  • Get sufficient sleep: Studies show inadequate sleep makes weight loss especially hard.
  • Drink enough water: Proper hydration is linked to more successful weight loss efforts.

Adequate water intake is considered to be about four to six cups for a healthy adult. Ask your healthcare provider if you have any conditions or factors that require more.

When and How Much to Eat

The timing of meals and snacks and how much you eat are important factors for weight loss, especially when you have thyroid disease.

Timing of Meals

Newer studies show that changing your timing of eating and the length of breaks between meals may help boost your metabolism and promote weight loss. One approach to this is an intermittent fasting diet, which can be done in a couple of ways:

  • Restricted daily timeframe: Each day, you only eat during a set period of between six hours and eight hours.5:2 approach: You eat regularly for five days, then for two days you’re limited to a single meal of between 500 and 600 calories.

Some people may have success with a grazing-all-day approach, which typically involves three small meals plus three snacks a day at regular intervals. Others have luck not eating anything after 8 p.m.

Check with your healthcare provider first before starting an intermittent fasting diet to make sure it’s safe for you.

How Much You Eat

It’s well established that your weight and weight-loss attempts are influenced by how many calories you eat.

The recommended calorie intake for adults is:

  • Between 1,600 and 2,400 calories per day for people assigned female at birthBetween 2,000 and 3,200 calories per day for people assigned male at birth

You may be surprised to learn that eating too few calories can stall your weight loss. That’s because your body goes into starvation mode and starts consuming muscle for energy instead of fat.

What’s ideal for you depends on many factors. A healthcare provider or a nutritionist can help determine what’s best for you.

Weight Loss Foods and Supplements

Some foods and nutritional supplements may help you lose weight despite your hypothyroidism.

Fiber

Fiber has been shown to help with significant weight loss in people with thyroid disease. Several things could contribute to this effect.

If you have frequent constipation, which is common in hypothyroidism, it’s likely due to slow digestion. Slow digestion can lead to weight gain or stalled weight loss. Fiber can help with this.

Fiber also reduces blood-sugar swings and lowers the glycemic load of foods, which is good for people with insulin resistance. Some experts recommend taking fiber supplements with high-carbohydrate foods to counter their effects on blood sugar.

In general, high-fiber foods are more filling and take longer for you to digest. This means more time before you get hungry again.

Other Weight-Loss Helpers

Some other foods and supplements may help, but most haven’t been studied as much as fiber, especially for their impact on people with hypothyroidism. They include:

  • Chia seeds
  • Cinnamon
  • Coconut oil
  • Grapefruit
  • Conjugated linoleic acid (CLA)
  • Caralluma
  • Hoodia gordonii
  • Green tea

No matter how “natural” or “healthy” something seems, remember that it can have negative side effects. Be sure to check with your doctor before adding foods and supplements to your treatment regimen.

Goitrogens: What Not to Eat

Some otherwise healthy foods can slow down your thyroid function, which can stall weight loss or lead to weight gain. These naturally occurring compounds are called goitrogens and include:

  • Cruciferous vegetables (spinach, kale, cabbage, cauliflower, broccoli, turnips, rapeseed)
  • Cassava
  • Lima beans
  • Linseed
  • Sorghum
  • Sweet potato
  • Soy
  • Millet

You can eat these vegetables in moderation, especially if they’re steamed or cooked since heat destroys problematic substances. However, you should be careful not to eat large amounts of these foods.

Soy is a special concern. Along with being a goitrogen, soy can block your body’s absorption of thyroid hormone. That can make your treatments less effective. This can pose a real problem for someone following a vegetarian or vegan diet, as soy is used in many meat-replacement products.

Movement, Exercise, and Workouts

Movement—sports, exercise, or other forms of physical activity—is an important part of any successful weight loss program and is particularly important for thyroid patients. That’s because it:

7 Essential Facts About Goitrogens and Diet

  • Boosts the metabolism
  • Reduces fluid retention and bloating
  • Makes you feel more energetic

Diet Drugs

Some diet drugs on the market can pose dangers for thyroid patients. If you want to try any of these drugs, be sure to weigh the pros and cons with a healthcare provider.

Saxenda and Wegovy

Saxenda (liraglutide) and Wegovy (semaglutide) may increase your risk of medullary thyroid cancer (MTC). Don’t take them if you have a personal or family history of MTC or multiple endocrine neoplasia syndrome type 2 (MEN 2).

This risk doesn’t appear to be higher due to hypothyroidism unless you have thyroid nodules, adenomas, or goiter. These abnormal growths are tied to an increased thyroid cancer risk.

Saxenda was originally created to help control diabetes. Levothyroxine, which treats hypothyroidism, can impair its ability to lower blood-sugar levels. This can interfere with both diabetes management and weight loss.

Wegovy can change how much levothyroxine your body absorbs, possibly raising your thyroid hormone levels to a dangerous degree.

Qsymia

Qsymia (phentermine/topiramate) isn’t recommended for anyone taking levothyroxine or liothyronine. Thyroid disease appears to make you more sensitive to the effects of Qsymia.

This diet drug and both thyroid medications can increase your heart rate and blood pressure. Taken together, they can put a strain on your cardiovascular system, which could result in heart disease.

Alli/Xenical

The drugs Alli and Xenical (which are both brand names of the drug orlistat) interact badly with thyroid medication. It may lower the effectiveness of your thyroid replacement hormones.

To counter this effect, you should take the medications at least four hours apart. A healthcare provider will likely monitor your TSH levels extra closely while you take orlistat.

Summary

Hypothyroidism slows your metabolism and makes other changes that can hamper weight loss. Other hormones that influence weight and appetite may be affected as well.

If you’re having trouble losing weight, ask your healthcare provider about testing your thyroid hormone levels. They can help determine if you need medication or a change in dosage.

You may be able to jumpstart your weight loss by getting enough sleep, staying hydrated, following a special diet, eating more fiber, avoiding goitrogens, and increasing your physical activity. Diet drugs may pose special problems for people with hypothyroidism because of drug interactions.

A Word From Verywell

Weight loss is never easy, and it can be significantly harder when you have hypothyroidism. You may have tried a lot of weight-loss strategies with little or no success. That doesn’t mean it’s a hopeless situation, though.

Try working with your healthcare provider on a healthy weight-loss plan. You may want to see a nutritionist for extra help. These professionals can help you develop a plan that focuses on healthy habits.

Also, try reaching out to other people with thyroid disease, either online or in your community. They can provide advice and encouragement as you work to find a plan that’s right for you.