Tubal ligation is not associated with weight gain, as the hormonal changes related to it are small to none. That said, tubal ligation is not something to be taken lightly. It is a permanent sterilization. One should make this decision with great care, not because one was "told" to do so. If you are happy with the number of children you have and are certain you're done with childbearing, it may be a good option for you. You should speak with a doctor to have them explain it to you in detail.