Breakfast
The need to break the all-night fasting in the morning was common among peasants and tradesmen who started their day early and got to work. It was not generally observed by the upper classes—perhaps because they slept later than peasants, and didn't get right to heavy work—and moralists frowned on it so strongly that some gentlemen felt the need to express shame for eating upon first rising.
Dinner
What eventually became the noon meal was considered the substantial meal of the day, a needed repast because of what you had been doing, and energy for the rest of the day.
Supper
From the word meaning "to sup," supper was served later and was simpler, often involving soup or sops: bread dipped in some tasty liquid.
...and that should have been enough. The sun would be down soon, and sleep would beckon. There was, however, a trend among the profligate that peeved the moralists but delighted the partakers.
If breakfast and little in-between meals drew the ire of moralists, how much more so the late meal after supper known as the reresoper. It was condemned unanimously by the church and heads of households as an unnecessary extravagance and an indulgence. Ranging from a full meal to just some snacks accompanied by lots of alcoholic drink, the reresoper was usually enjoyed by a few friends in a private room rather than the whole household in the hall, as was proper. Loud laughter, crude jokes, gambling, and flirting were some of the vices associated with this meal, which often dragged on until after midnight and resulted in many a hangover the next day. [Food in Medieval Times]Reresoper [the rear-supper, that follows regular supper]
If it wasn't enjoyed by "heads of households" then one pictures the younger generation unwilling to follow a philosophy of "early to bed, early to rise," and instead staying up late and carousing. I cannot help thinking that Taco Bell's "Fourth Meal" marketing campaign serves exactly the same population.
