I had these when I was breastfeeding. I did not notice any weight gain, but I have always been physically active. Supposily they make you want to eat more, too, but I was eating more anyway because I was breastfeeding so I do not know if it was the shot or the nursing. I used them 9 months with my first son, and then I went on birth control for a little while, and then I attempted to get pregnant again ( I did so after 2 months). Supposily it can take up to a year to get pregnant again after doing the depo provera shots. They are expensive, it was cheaper for me to go back on the pill after my second son was born, so that is what I did.