After Christian hegemony of the Roman Government. Fasting days increased as Byzantine increased. Meaning government Titled and Clerical offices. The Wage-workers were already fasting, meat was a rarity. Titled and Clerical offices received the benefits of office meat and wealth was a benefit. The Great Fast is a period when food was the scarcest in these times until modern agriculture. The increasing of the other fasts is highly conclusive.
All four fasts of the Church practice were done seven days before the feast day, and if feast day landed on a fast day, the fast day was not a Strict Fast, ie fish, wine, & oil were allowed.