Hi, Thanks for writing in. Implanon does become less effective in overweight women as the concentration of etonogestrel ( the active drug in implanon) becomes less in the blood stream. Regarding the movement, I do not think it would make the implant any less effective. The only consequence would be that a larger incision may be needed when your physician gets down to removing it. Given your weight and the fact that Implanon doesnt protect against sexually transmitted diseases including HIV-AIDS , I would suggest you speak with your physician and consider another method of contraception. Hope this helps Regards