This really is only going to be helpful to a few people, I realize, but I lost 40 pounds without even trying by taking a job picking and packing in a warehouse.  (Basically I walk for 8-10 hours a night.)  Unfortunately I hit a plateau with another 50-80 pounds left to go, but I just managed to badger my bosses into putting me in an even more active position, so hopefully that will push me over the hump for a while. *crosses fingers*.