If the only thing that could reasonably be looked at as causing the weight gain is the implanon, then I can't imagine there being anything to actually stop the weight gain except going off it. Certain pills made me gain or lose weight, and the only way to fully stop it was to switch. I'm sure you can increase your exercise and lose some, but sounds like you definitely need to talk with your doctor about this. You don't want to find yourself at an unhealthy weight that's bad for your heart, your arteries, your bones, could lead to diabetes, high blood pressure etc. If I were you, I'd rather switch birth controls.