Underactive Thyroid and Weight Loss

By Dietitian, Juliette Kellow BSc RD

Q: After gaining weight and having no energy to exercise, I was diagnosed with an underactive thyroid gland. Now having been on thyroxine I have more energy and am back at the gym twice a week. But instead of losing weight as my doctor promised, I’m continuing to put on weight. Does this mean that even when treated, an underactive thryroid will make it impossible for me to lose weight?

A: An underactive thyroid condition occurs when the thyroid gland fails to produce sufficient amounts of the thyroid hormones that help regulate the body’s metabolism.

A lack of these hormones decreases metabolism, causing symptoms such as weight gain, tiredness, depression, poor concentration, dry skin and constipation – all things you’re likely to be familiar with. Fortunately though, as you have discovered, thyroid disorders can be controlled by medication.

Many people with an underactive thyroid gain a lot of weight before a diagnosis is made or if the condition is poorly controlled. But if you are being prescribed the correct dose of thyroxine, there’s no reason why you can’t lose weight through sensible eating and taking more exercise.

However, you should bear in mind that treatment with thyroxine doesn’t result in an immediate recovery – it can take up to nine months for the symptoms to improve and even longer for you to feel better.

If you are sticking to your daily calorie allowance recommended by WLR, you should be losing weight at your chosen rate. The fact you’re not achieving this indicates one of two things – either you are underestimating your calorie intake, or your thyroid problem is not adequately controlled.

I suggest you keep a food diary for a week, making sure you record every single item you eat. If, at the end of the week, you discover you really are sticking to your calorie allowance, you might want to see your GP to check whether you are having the correct dose of thyroxine.

You’ll find more information about hypothyroidism on the British Thyroid Foundation website, www.btf-thyroid.org