I"ll jump in with my 2 cents also. I lost 70 pounds and have kept it off for 2+ years through a weight loss study that was comparing a low-carb (Atkins style) diet to a low fat diet (called DASH).

One of the researchers on the study has been doing weight related research for 20 years, and he had a really interesting perspective. In his experience, there were 2 key things to taking off weight and keeping it off for most people: food journalling and social support. That's it. The rest is personal preference.

Working out (whether it's walking 3x a week or cycling 6x a week) doesn't predict long term success, although it does seem to help. There is no one diet that has been proven to be better than another. The best diet and workout plan is the one that you can stick with. Find something that works for you and stick with it.

In my experience, food journalling and social support are the key. When my study went from weekly meetings to monthly meetings, I stopped writing down my food and had trouble keeping my weight stable - I would go up by 5 pounds and down by 4. I just joined Weight Watchers for the meetings, and started writing down my food again, and the 10+ pounds I had gained back have come back off.

Good luck finding the plan that works for you. There is no magic bullet, but with attention to what you eat, you can lose the weight you want.