Fasting on Sundays? No!

"CARTHAGE (398). Held November 8th, 398, under Aurelius of Carthage, at the head of two hundred and fourteen or two hundred and fifteen bishops, including St Augustine. One hundred and four canons were published . . . 

The 64th declares those persons not to be catholics who fast upon Sunday."

Landon, E. H. (1909). In A Manual of Councils of the Holy Catholic Church. Edinburgh: John Grant.

"[DS 454] 4. If anyone does not truly honor the birthday of Christ according to the flesh, but pretends that he honors (it), fasting on the very day and on the Lord’s Day, because, like Cerdon, Marcion, Manichaeus, and Priscillian, he does not believe that Christ was born in the nature of man, let him be anathema."(Council of Braga II, 561AD)

(Anathemas against Heretics, especially the Priscillianists) Denzinger. The sources of Catholic dogma (p. 93).

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