Mentioning previous answers is not intended to discourage further questions. Follow-on questions, information, and debate is welcome.

The FAQ points to "When did having three meals a day--breakfast, lunch, and dinner--become the norm?" at https://www.reddit.com/r/AskHistorians/comments/10we0z/when_did_having_three_meals_a_daybreakfast_lunch/ , answers by /u/Talleyrayand (pointing out that three meals is not the norm worldwide) and [deleted].

There's also "How did the three-meal day become standard throughout the world? We’re there any cultures that ate more or less meals in a day?" at https://www.reddit.com/r/AskHistorians/comments/7vk9p4/how_did_the_threemeal_day_become_standard/ , with an answer and sources by /u/VivaLaVodkaa , and also /u/AshkenazeeYankee.

Also see "Did the ancient Romans really only eat one meal a day?" at https://www.reddit.com/r/AskHistorians/comments/7700g7/did_the_ancient_romans_really_only_eat_one_meal_a/ , where XenophonTheAthenian ... well, addresses that.

"Did early humans eat 3 meals a day? When/where did to tradition of eating 3 meals a day start?" at https://www.reddit.com/r/AskHistorians/comments/1bem68/did_early_humans_eat_3_meals_a_day_whenwhere_did/ : natarey touches on medieval practice, with pointers to sources. (This used to be in the FAQ but has been removed.)

"How did the distinction between the 'English' and 'Continental' breakfasts come about?" at https://www.reddit.com/r/AskHistorians/comments/145mof/how_did_the_distinction_between_the_english_and/ : agentdcf touched on the changes to breakfast brought on by meal-times moving later in the day.

I will go out on a limb to point to a BBC News Magazine article: Denise Winterman, "Breakfast, lunch and dinner: Have we always eaten them?", 15 November 2012, http://www.bbc.com/news/magazine-20243692 . A lot of historians are cited.