Good Afternoon. I Am Having The Left Side Only Of

Good afternoon. I am having the left side only of my thyroid surgically removed. I have a toxic nodule and I have hyperthyroidism. I have gained a lot of weight, 30 pounds, and I have hyperthyroid. I have never been this overweight in my life. My doctor said that I would lose the weight that I gained once I have the left side removed... is this true? Because hyperthyroid you lose weight. I have gained. Will I lose the 30 pounds I gained once my thyroid is removed?