One of the most frustrating things I hear from clients with thyroid conditions is that they've been dismissed — told their weight struggles are simply a lack of willpower. The reality is far more nuanced, and you deserve an honest explanation.
How the thyroid affects your weight
Your thyroid gland produces hormones — primarily T3 and T4 — that regulate your metabolism. Essentially, they control the rate at which your body burns energy. When the thyroid is underactive (hypothyroidism), metabolism slows. This can lead to weight gain, fatigue, fluid retention, constipation and feeling persistently cold. When it's overactive (hyperthyroidism), metabolism speeds up, and unintentional weight loss can occur.
But thyroid treatment doesn't always mean weight loss
Many of my clients expect that once their thyroid levels are corrected with medication, their weight will simply normalise. For some people this happens — but for many it doesn't, and they're left confused and disheartened. The truth is that hypothyroidism can cause only modest weight gain (typically 2-5kg), and much of this is fluid rather than fat. Other factors — insulin resistance, disrupted sleep, fatigue-related inactivity and changes in appetite — often play a greater role in weight challenges than the thyroid alone.
What diet can actually help with
While there's no specific "thyroid diet," there are dietary approaches I find genuinely useful in my clinic:
- Anti-inflammatory eating — conditions like Hashimoto's thyroiditis have an autoimmune component, and an anti-inflammatory dietary pattern (rich in vegetables, oily fish, wholegrains, olive oil) may help manage inflammation
- Selenium and iodine — both are important for thyroid hormone production; Brazil nuts are a great selenium source, and iodised salt and dairy provide iodine
- Adequate iron — iron deficiency can impair thyroid function; ensuring adequate intake is important especially for women
- Being cautious with raw goitrogens — large amounts of raw cruciferous vegetables (kale, broccoli, cauliflower) can theoretically interfere with thyroid function in iodine-deficient individuals; cooked versions are generally fine
What about supplements marketed for thyroid health?
I'd urge caution. Many supplements marketed for "thyroid support" are unregulated and some contain thyroid hormone derivatives that can interfere with your medication. Always discuss supplements with your endocrinologist and dietitian before taking them.
The most important thing
If you're struggling with your weight alongside a thyroid condition, please know that it's not your fault and there is real, practical support available. Working with your endocrinologist and an APD who understands thyroid conditions can make a genuine difference to how you feel.