I think that Bento box is the right to count the calories, and try to lose weight. You can have a little bit of vegetables plus a little bit of protein, some starch. In that way you can manage your meal in that meal period of the day.
You don't have to go to a restaurant, or to a fast food place and not knowing what you are going to eat. You prepare it that day; you know what you put inside. Basically, that is going to be your meal. It's a great way to manage the calories and the type of food that you are eating.