Try the Morning Banana Diet!
Apparently this is hugely popular with girls in japan: Link
You eat a banana and room temperature water in the morning, eat anything you like for lunch and dinner (by 8 p.m.). A three o'clock snack is okay, but no desserts after meals, and you have to go to bed before midnight.
All the grocery stores in japan are out of bananas because this diet is so popular. It actually sounds like it makes sense to me. They're essentially just telling girls to eat breakfast, so try it!