Thyroid and Weight Gain
Thyroid hormones control your metabolic rate — an underactive thyroid slows it and commonly causes modest weight gain.
Plain English
Patient-Friendly Explanation
Thyroid hormones control your metabolic rate. An underactive thyroid (hypothyroidism) slows metabolism and commonly causes modest weight gain, while an overactive thyroid tends to cause weight loss.
Medical
Clinical Definition
Thyroid hormones (T4/T3) regulate basal metabolic rate. Hypothyroidism reduces resting energy expenditure and is associated with modest weight gain (typically 2–5 kg, largely fluid and fat); hyperthyroidism increases expenditure and typically causes weight loss. Weight effects are usually reversible with appropriate thyroid treatment, but thyroid dysfunction explains only a small minority of obesity — most overweight patients have normal thyroid function.
Key Insight
Why It Matters
Patients often blame their thyroid for weight gain — and while it deserves checking, an underactive thyroid explains only a few kilograms. The clinic tests thyroid function when history or examination suggests it, but treats the weight as its own problem in most people.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: August 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
