You make your own rules about what matters.
Box Lunch Lifestyle isn't about weight loss. It's about doing things "better," and doing more of the things that make you YOU. If you're making your own lunch, you're more likely to eat better food--if not necessarily low-calorie food.
If you want to change how much fat you have on your body, take care of your whole body. Eat good lunch food, but pay attention to how you use your lunch time, too. It's a way to flex ALL of your discipline muscles.