While it took me 53 weeks to lose 85 lbs (and I WAS very committed to my lifestyle change), I am 50+ and have a sedentary job.

That being said, I think that one of the most important reasons that I was successful is that I did NOT put a time limit on it. Every time I have attempted to lose weight with any type of time-bound goal, I have failed. Over, and over again.

So, pick a plan, start your lifestyle change, and let your body come along for the ride

I would say a year minimum, and probably a year and a half.

Excellent thread. I am always astonished at the range of responses to questions like these. The stuff "diet" books don't tell you!