Hi there! Yours is a great question, with a really simple answer! What works is what works for YOU!
What I mean by this is that you are RIGHT -- there are hundreds, if not thousands of diet plans out there. All of them have the same basic premise -- if you cut calories, you will lose weight. Some cut calories by eliminating foods or food groups. Others by counting calories to make sure you aren't eating too much. Others provide you with the food, thereby ensuring that calories are cut.
SO, what works is the plan that fits into your lifestyle so that you will stick with it. I personally do Weight Watchers because all foods are allowed, but you have to account for your intake so that you expend more calories than you take in. Others prefer to Calorie Count, which is pretty much the same. Only I am math challenged! So it is easier for me to count WW points (22 per day for me!) than it is to count calories (1200 -1500)!!! Others like food delivery type programs, such as Nutrisystem or Jenny Craig. Still others like Atkins and have great success with it (I couldn't do that one for very long -- gotta have my pasta!!!

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What does the trick is your own personal dedication and motivation and DECISION to change your life. HOW you get there is really your own path that you have to find.
If you check the boards, there are success stories in pretty much all diet program threads. So it really comes down to deciding HOW you want to live the rest of your life and then making the CONSCIOUS DECISION to do so.
Maybe not the clear answer you were hoping for (i.e. I use plan X), but I think it is pretty accurate with respect to the reality of lifestyle change...
Kira