I'm iun the same boat as you in terms of needing t lose weight. The yo-yo effect is real though so you'll have to be carefull. Using my own experience, in the last 16 months I went from 228 in Jan 08 to 203 in July 08 and have now topped out (I hope) at 238. PArt of my problem is a medication issue, but mosly its a discipline and lack f motivation problem. I had almost a 1000 miles in by this time last year and now I'm about to hit 100 for the year. That said, I know what I need todo but changing the habits is tough.
Good luck, and i hope you make this change stick!