Height and other similar features are controlled not just by one gene, but rather, by multiple (often many) genes that each make a small contribution to the overall outcome. This inheritance pattern is sometimes called polygenic inheritance
Because the gene is an inheritance of our ancestors, weight is something you gain or lose depending on how balance your health is. The reason why our weight can't be controlled by the gene is because the gene has different traits coming from each parents(50%) and grandparents(25%), and either parents has different weight, so it will be hard for the gene to capture one specific weight from both sides.
