If you gained the weight back, the diet didn't work
Not saying this to make anybody feel bad or anything, but to consider a diet successful, you can't gain the weight back. That means that you didn't learn a way of eating you could maintain for life. It has to be something you understand and enjoy, a way you WANT to eat.
ALL diets work to lose weight, but the only ones that will work for permanent weight loss are the ones that teach you to change your lifestyle permanently. Remember old habits = old body. There's just no way to get around that.
Good luck whatever you do
My blog, This is not a Diet:http://notsobigk.wordpress.com
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