I lost quite a bit of weight before this pg. I think it is a great thing to do. Gets your body into top shape to be carrying a bub - the healthier you are at the begininning, the easier it should be. That said though, I wouldn't do anything extreme - a sensible diet & some exercise. And of course, once you are pg, don't worry too much. You will gain weight, but if you are sensible it may not be much. Some heavier people even lose body fat while pg! So as the baby grows - they shrink!

All the best with it.