ANY plan is a "diet" if you treat it as something you can be "done" with and go back to eating "normal" again. Period.

I know quite a few people who've managed to take weight off and maintain on other plans. My friend Elaine did WW, and she's maintained her 50-lb loss for more than 3 years and still going. She has committed herself to healthy eating and exercise, and her overall health is great.