Art History student here! I actually just took a class and wrote a paper on the androgynous appearance of Jesus. Though I can't tell you what a 1st century Jew may have looked like, I CAN tell you why the effeminate looking Christ is fairly common.

First, Christian art as well as Christianity itself was illegal for many years, so christians appropriated depictions of Pagan gods into a "cover" for Jesus Christ. With that being said, one of the gods they used was Apollo who could also be pictured with womanly characteristics. They used a lot of other pagan figures like Orpheus and Dionysus as well.

Once christianity was finally tolerated in the empire in the fourth century, Christ had already been dead for so long that people took these depictions as a basis and also tried to give him characteristics that would make him relatable to certain groups. In this case, Christ was shown to relate to his female followers. My favorite art work representing this is this Mosaic in Ravenna Italy where you can see a much more "feminine" Christ in the center with John the Baptist. It was said that by portraying him with feminine characteristics, Christ then appeared to be a "nurturer" of life and of souls as well as giving him a a "life-giving" characteristic. They used these to differentiate Jesus and his powers from the apostles, too.

I know this doesn't really address biblical passages and how that may influence these portrayals but I hope I shed some light on it! If your interested in reading more on this information, check out the Christ Chameleon chapter in the book, "A Clash of Gods" by Thomas F. Mathews. I'm happy to share more sources as well.

I can't think of any NT passages that imply that. Isaiah has a prophecy about the messiah (~740 years before Christ showed up) that predicted him being very plain of face, so to speak.

“He had no beauty or majesty to attract us to Him, nothing in His appearance that we should desire Him.” Isaiah 53:2

Can I ask a related question, is their any proof of the theory that the Jesus we see in paintings was actually based off of Caesar Borgia?

The origin of most depictions of Jesus we are familiar with come from the Italian Renaissance, when shoulder-length hair was at the height of fashion. If he does look emaciated, it's probably done to display his vulnerability, humanity, suffering after the passion, and whatever other artistic themes the painter was looking to stick in there. Painting Jesus was also a good excuse to conduct studies of anatomy, where the model would be a cadaver.

At one point a team of "Researchers" from the BBC (which I put in quotation marks, as the BBC is a broadcaster, not an academic institution) reconstructed what the average person born in first-century Judea would look like, and in all probability Jesus wouldn't be too different.

For depictions of Jesus in Italian art, I'd cite a book I recently read by Vittorio Sgarbi about Italian art in the early renaissance and late middle ages; I'll cite it properly when I get home. Sgarbi is an Italian art critic and academic who's become an entirely disagreeable TV personality, blabbering about things he knows nothing about, but still manage to turn into a normal person when talking about art.

It's always very important to read more than one verse. In some cases you find that a passage taken out of context has the complete opposite message when isolated. Appears to me that the passage about the hair in Corinthians is in fact deconstructing a tradition, not supporting it. "For as the woman is of the man, even so is the man also by the woman; but all things of God. Judge in yourselves: is it comely that a woman pray unto God uncovered? Doth not even nature itself teach you, that, if a man have long hair, it is a shame unto him? But if a woman have long hair, it is a glory to her: for her hair is given her for a covering. But if any man seem to be contentious, we have no such custom, neither the churches of God. (‭1 Corinthians‬ ‭11‬:‭12-16‬ KJV) if they are both "of God." Then why the division? See? Ones a glory and one a shame? If she serves him and he God? Why two customs? And any controversy isn't recognized since they have no such custom. (Regarding one or the other) It doesn't matter. Goes on to say: Now in this that I declare unto you I praise you you you NOT, that ye come together not for the better, but for the worse. For first of all, when ye come together in the church, I hear that there be divisions among you; and I partly believe it. (‭1 Corinthians‬ ‭11‬:‭17-18‬ KJV) it's a scorning of division. Division based upon outward appearance. The nature of flesh isn't your salvation basically. That's not why your in the church. As far as the emaciated look. "First deny yourself." He spent 40 days being tempted without eating. So there was definitely a starved Jesus at least at that point. And as far as blending in goes, head coverings were a standard for that area during that time. Since most time was spent outside at the mercy of the sun. And since beard were also standard that leaves very little to distinguish between thousands of passing people. How he's portrayed is only a reflection of what people wanted him to be. Appearance was basically contrary to the entire book. And his own teachings.