ELI5 Breakfast - Is it the most important meal of the day?

Why is breakfast "the most important meal of the day"? Where did the phrase even come from? ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: bca1849, mredding, shleppenwolf & lyrical_myrical   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected] ... we love hearing from you!