Are you talking about bento boxes served in America? I lived in Japan for 5 years and even a 7-11 bento will have 15+ different types of food in them pretty regularly (Salmon, rice, umeboshi, misoshiru, tofu, wakame, burdock root, carrot, salad with a few ingredients, another protein, tsukemono, and nimono (with a few other ingredients). Now if you look a traditional kaiseiki dinner, you're looking at 30+ types of food included. Don't get me wrong, I love ban chan and eat Korean food regularly because of the ban chan included, but bento boxes were pretty much created to serve a lot of different foods in small portions.

This concept is well recognized in Japan, hence bento boxes having a small portion of a variety of veggies, foods, and toppings. I’m glad there is a study that supports this idea!