Depending what you consider my start date (I started running regularly before I changed my eating habits), I've been losing weight for about 15-16 months already. At my current rate I'm losing between 2-4lbs/month so if I decide to stop at a healthy BMI (155lbs) that would mean that I'll be done in 6.3 months (assuming a loss of 3lbs/month) but if I decide to go down all the way to me lower end of my goal weight it'll be a total of 11.3 months.
Granted, that's assuming that I consistently lose 3lbs/month but there's a good chance my weight loss could slow down even further the closer I get to goal. So who knows?
On the other hand, my weight loss speeds up quite a bit if I get sick, so hopefully that doesn't happy but it could mean I hit goal sooner.
Anyways, it looks like it will have at least taken me about 2 years to reach goal.