Either or...or both. But it certainly had something to do with days devoted food...that much is clear when the whole chapter is read. For example:
Rom 14:2 For one believes he may eat all things, but he who is weak eats only vegetables.
This suggests vegetarianism brought about by fear of eating meat brought in the "shambles"...the meat markets...because of concerns they may have come from pagan worship sacrifices. These concerns were addressed by Paul elsewhere:
1Co 10:25 Eat whatever is sold in the meat market, asking no questions for conscience' sake;
1Co 10:26 for "THE EARTH IS THE LORD'S, AND ALL ITS FULLNESS."
1Co 10:27 If any of those who do not believe invites you to dinner, and you desire to go, eat whatever is set before you, asking no question for conscience' sake.
1Co 10:28 But if anyone says to you, "This was offered to idols," do not eat it for the sake of the one who told you, and for conscience' sake; for "THE EARTH IS THE LORD'S, AND ALL ITS FULLNESS."
1Co 10:29 "Conscience," I say, not your own, but that of the other. For why is my liberty judged by another man's conscience?
1Co 10:30 But if I partake with thanks, why am I evil spoken of for the food over which I give thanks?
1Co 10:31 Therefore, whether you eat or drink, or whatever you do, do all to the glory of God.
This is saying essentially the same thing as in Romans. Paul was addressing a matter of conscious. But in Romans Paul weaves in fasting as an example of another eating matter dependent upon conscious. Some Jewish Christians would fast on specified days determined by the Jewish religion (not scripture). For example:
Luk 18:11 The Pharisee stood and prayed thus with himself, 'God, I thank You that I am not like other men—extortioners, unjust, adulterers, or even as this tax collector.
Luk 18:12 I fast twice a week; I give tithes of all that I possess.'
The man considered himself righteous because he fasted twice a week. That's not a scriptural command.
1 At that time Jesus went through the grainfields on the Sabbath, and His disciples became hungry and began to pick the heads of grain and eat. 2 But when the Pharisees saw this, they said to Him, "Look, Your disciples do what is not lawful to do on a Sabbath." 3 But He said to them, "Have you not read what David did when he became hungry, he and his companions, 4 how he entered the house of God, and they ate the consecrated bread, which was not lawful for him to eat nor for those with him, but for the priests alone? 5 "Or have you not read in the Law, that on the Sabbath the priests in the temple break the Sabbath and are innocent? 6 "But I say to you that something greater than the temple is here. 7 "But if you had known what this means, 'I DESIRE COMPASSION, AND NOT A SACRIFICE,' you would not have condemned the innocent.
There's a few issues here.
1. The Pharisee's had instituted a plethora of manmade, non-scriptural rules and regulations for what constituted "work" on the sabbath. These man made rules were strictly enforced to point of ridicule. For example:
Joh 9:13 They brought him who formerly was blind to the Pharisees.
Joh 9:14 Now it was a Sabbath when Jesus made the clay and opened his eyes.
Joh 9:15 Then the Pharisees also asked him again how he had received his sight. He said to them, "He put clay on my eyes, and I washed, and I see."
Joh 9:16 Therefore some of the Pharisees said, "This Man is not from God, because He does not keep the Sabbath." Others said, "How can a man who is a sinner do such signs?" And there was a division among them.
The amount of "work" that had to be done was silly here...and it was "work" that was an act of compassion and mercy. There is nothing in OT scripture that says we shouldn't do this.
By the time of the incarnation of the messiah the Jews had wandered far from what was scriptural. Their traditions and customs were (and are) often considered to be the final word on interpretation of scripture. These often went against the commandments of God:
Mat 15:7 Hypocrites! Well did Isaiah prophesy about you, saying:
Mat 15:8 'THESE PEOPLE DRAW NEAR TO ME WITH THEIR MOUTH, AND HONOR ME WITH THEIR LIPS, BUT THEIR HEART IS FAR FROM ME.
Mat 15:9 AND IN VAIN THEY WORSHIP ME, TEACHING AS DOCTRINES THE COMMANDMENTS OF MEN.' "
The notion that Jesus Christ broke any of the ten commandments that were created by him, spoken by his lips, and written by his hand is a non-starter. That would mean that Jesus Christ was a sinner. He wasn't of course.
And, HE is a HUMAN - just like you.
What WAS 'taught' here' is there is a higher princle than slavishly 'following the LAW'.
"Don't you pull an ox out of a ditch on the Sabbath?"