It's different for everyone! I've been on Alesse, Yasmin and Marvelon On both Alesse and Yasmin I didn't have any weight gain, but I gained about 7 pounds on Marvelon. One of my friends was on Alesse...
They don't always make you fat; some women lose weight when taking them. They affect your hormones so naturally they affect your weight, but not every woman reacts the same way.