Get in Shape in 12 Weeks or 12 Months?

If you could get in shape in 12 weeks but put the weight back on afterwards or do it in 12 months and never have to do it again which would you choose? Depending on these, your going to choose different diets, different training, different lifestyles.  These choices are all fine as long as you know what those choices feed... If you want to keep the weight off then choosing fad diets and hours of cardio probably isn't the right choice But if you only care about the photo at the end of the diet then thats cool too.