Losing Weight After a Thyroidectomy: What's Realistic

Some people gain a little weight after a thyroidectomy, some gain more, and many gain none. Across 17 studies the average was about 2 kg over roughly two years, more after surgery for an overactive thyroid. A Melbourne study found no significant change on average. Once your thyroid levels are right, losing weight works the same way as for anyone else. Levothyroxine isn't a weight-loss tool, so the useful steps are checking your dose is right and then the everyday basics: food, movement and sleep.

If the scales have crept up since your surgery, or you are worried they will, here is what the research actually shows, why it happens to some people more than others, and what helps.

How much weight do people gain after a thyroidectomy?

Less than many people fear, and it varies a lot:

• A 2021 review of 17 studies and more than 3,000 people found an average gain of about 2.1 kg over about two years after a total thyroidectomy. It was about 5.2 kg when surgery was for an overactive thyroid, about 1.6 kg for a goitre, and about 1.3 kg for thyroid cancer. Younger people tended to gain more.
• A study from the Alfred Hospital in Melbourne followed 79 people for at least ten months and found an average change of just 0.06 kg, which was not significant. Some people gained and some lost, and the authors described weight change after surgery as unpredictable.
• A US study found people gained about 1.8 kg more in the year after surgery than similar people without thyroid disease.

So the honest picture is: on average a little, for some people a lot, and for many none.

Why some people gain more

Surgery for an overactive thyroid

If your thyroid was overactive before surgery, you may have lost weight because of the extra hormone. The American Thyroid Association explains that this weight loss reverses once thyroid levels return to normal, and that people may have got used to eating more while their thyroid was overactive. That is the main reason gains are bigger after surgery for Graves' disease or an overactive nodule.

Changes in habits

A 2022 review concluded that weight gain after thyroidectomy seems to be related more to changes in habits after surgery, such as eating and activity during recovery, than to anything permanent.

Your dose

If your levothyroxine dose is too low, an underactive thyroid can add some weight. The first dose after surgery often needs adjusting, so a dose check is the first step if your weight is climbing. Our guide to signs your dose is too high or too low explains what to look for.

Life stage and other causes

Age, some prescription medicines and poor sleep all affect weight too. Around menopause, body composition shifts towards more fat and less muscle, even when total weight changes little. Your GP can help sort out what is playing a part.

Is your metabolism "broken"?

No. You may read that metabolism drops by a large amount after a thyroidectomy. The research doesn't support that. In a study that measured it directly, resting energy use in people on levothyroxine was only about 4% lower than in healthy people, a small difference. And once levels are right, the American Thyroid Association says the ability to gain or lose weight is the same as for people without thyroid problems.

Can you lose weight after a thyroidectomy?

Yes. In one Italian trial, a single session with a dietitian before surgery prevented the weight gain seen in people who didn't have one. People on levothyroxine have lost weight with diet changes too, and in one study a weight-loss medicine worked as well for people with a well-treated underactive thyroid as for people without one. The steps that help are the same as for anyone:

• Check your dose first. Make sure your levels are in range before judging anything else.
• Eat in a way you can keep up. Enough protein, plenty of vegetables, fewer drinks with added sugar. Higher-protein, reduced-energy eating can help with appetite and weight management in general.
• Move regularly, including muscle strengthening on two or more days a week, as the Australian guidelines suggest.
• Protect your sleep. Short sleep is linked with hunger hormones that push appetite up.
• Get help. A dietitian can make a real difference, especially early on.

Don't change your dose to lose weight

The Australian levothyroxine leaflet says it should not be used for weight loss. Doses that are too high can cause serious heart and bone problems. A trial that changed people's doses found no improvement in weight or body composition, and the American Thyroid Association notes that any weight lost on extra hormone is usually regained.

Weight-loss medicines and your thyroid tablet

If you start a weight-loss medicine such as semaglutide or tirzepatide, ask your doctor when to recheck your thyroid levels. Losing weight can lower the levothyroxine dose you need, and some of these medicines may change how tablets are absorbed. After a total thyroidectomy you have no thyroid of your own to buffer a change, so a check matters more. If you have had thyroid cancer, talk to your specialist before starting one.

Where ThyroBase fits

ThyroBase is not a weight-loss product and makes no weight claim. It is a daily morning and evening nutrition powder, a food rather than a medicine, made with plant protein, greens and minerals, that sits alongside your thyroid medication, never instead of it. Both serves contain minerals, so keep them several hours away from your tablet. If you are working on your weight, it is worth talking through how it fits your day with your dietitian. Here is who ThyroBase is, and is not, designed for.

Weight after a thyroidectomy is usually a small, manageable change, not a sentence. Check the dose, then do the basics.

Frequently asked questions

Do you gain weight after a thyroidectomy?

Some people do, many don't. Across 17 studies the average gain was about 2 kg over two years, higher after surgery for an overactive thyroid. A Melbourne study found no significant change on average. If your weight rises a lot, ask your doctor to check your levothyroxine dose.

How can I lose weight after a thyroidectomy?

First make sure your thyroid levels are in range. After that, the same things work as for anyone: a sustainable way of eating with enough protein, regular movement including strength exercise, and good sleep. A dietitian can help. Don't change your levothyroxine dose to lose weight.

Does levothyroxine help with weight loss?

No. The Australian leaflet says levothyroxine should not be used for weight loss, and too high a dose can cause heart and bone problems. A trial that changed people's doses found no improvement in weight or body composition.

Why did I gain weight after my thyroid was removed?

Common reasons include regaining weight lost while your thyroid was overactive, changes in eating and activity during recovery, a dose that needs adjusting, and other factors like age, sleep and some medicines. Your GP can help work out which apply to you.

Can I take weight-loss medicines after a thyroidectomy?

Talk to your doctor. Weight loss can lower the levothyroxine dose you need and some of these medicines may affect tablet absorption, so your thyroid levels should be rechecked. If you have had thyroid cancer, talk to your specialist before starting one.

The honest takeaway

Weight gain after a thyroidectomy is real for some people, but it is usually modest, often linked to a dose that needs adjusting or to life changes during recovery, and it is not permanent. Get your levels checked, focus on food, movement and sleep you can keep up, and get support from a dietitian. Your effort counts.

ThyroBase is a nutritional supplement and is not intended to diagnose, treat, cure, or prevent any disease. It is designed to sit alongside your thyroid medication, not replace it. This article is general information, not medical advice. Never start, stop or change a supplement or prescription medication without speaking to your doctor or pharmacist first.

References

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