The most positively life changing one for me was the Whole 30: http://whole30.com/
And this is really the main key with diets and healthy eating. You gotta change your habits.
But in that respect, you could do similar things without the restrictions: Simply work on changing the habits without eating more. Take a while to focus on cutting out most sweetened beverages: Some time to eat more veggies, more grains, adjust your eating to reflect when you are hungry, and so on.