Well, from what I could gather. Its a mixture of both. Because of the huge amounts of hormornes in the depo, it increases estrogen and the body thinks it is preparing for childbirth, therefore it mimics pregnancy and also increased appetite. The weight gain on depo is confusing because at first I had not changed any eating habits, but was steadily gaining weight that would not shift. Then, my body became used to the starchy carbs I was craving and the habit was formed. Now that I am off that crap, I am regaining control again. Every body is different but depo can most certainly be a cause of weight gain and loss of bone density/hair. Dont know what kinda BC to use now but am going to do my research properly this time. Was thin on the mini-pill back in the day... hummm