I dropped between 40 and 50lb over the course of 6 months or so. a) I got a treadmill and started running (treadmills are good because you can stay in and watch anime while exercising) and b) I replaced all my snacks with apples.

That's what really puts on the weight: snacking. I have an almost bottomless appetite, I always want to be eating something. When that something is low in calories and high in good stuff, it's quite a low effort way of cutting unnecessary junk out of your diet.