Thyroid Imbalance Affects Weight Management The thyroid is a small, butterfly-shaped gland located in the neck that plays a major role in regulating your body’s metabolism—the rate at which you burn calories and produce energy. It does this by producing two key hormones: T3 (triiodothyronine) and T4 (thyroxine). When the thyroid becomes imbalanced—either overactive ( hyperthyroidism ) or underactive ( hypothyroidism )—it can seriously disrupt weight management. Hypothyroidism (Underactive Thyroid) and Weight Gain When the thyroid doesn’t produce enough hormones: Metabolism slows down, leading to fewer calories burned at rest. You may gain weight, even without a change in diet or activity level. The body retains more salt and water, contributing to bloating and puffiness. Fatigue and low energy make it harder to stay active or exercise consistently. This weight gain is typically modest (5–10 pounds) but persistent and difficult to lose without treating the root cause. Hyperthyroidism...