Diets never work - short term weight loss is all a diet will achieve and most have low nutritional values, losing nothing more than water.
Lifestyle change is the only way - healthy eating, proper fluid intake and exercise. That's all WW is, but as a structured plan it does work and it takes the hassle out of working out a plan for yourself - at a cost. But the minute you finish, you cannot go back to your previous eating/drinking habits. If you do, hey presto, the weight comes back.
Rocket science? I think not............
GG