But that's the point. A diet is not something that you do a few months after which you get and keep a killer figure while returning to eating whatever you want. A diet should be the preliminary to a permanent shift in eating habits.

This is very true. We just need to avoid recommending unsustainable diets based on calories in/out thinking. Since they all ultimately fail. Also why settle for a decreased metabolic rate when you could actually increase it and enjoy the extra energy instead. No need to feel miserable the rest of your life.