In class the topic was medieval times since we were reading Romeo and Juliet, and after one of the students mentioned something she started talking about how being obese in Medieval times was the beauty standard, since it basically meant you were rich enough to overeat. And that most men back then found overweight women very attractive compared to skinnier women.
To my knowledge, and to grossly simplify what a friend told me, in the past there were skinny, "Plump", and obese women, and men prefered "Plump" women since they were more likely to survive childbirth and were also attractive. I'm not sure if she's confusing plump for obese or not, or which one of them are in the wrong, which is why I'm asking.
She also mentioned how Juliet was probably 12, and she said that most men, regardless of how poor they are or how little power they had, would be marrying and having kids with underaged girls. I do know this happened, but my question is was it really all men doing this, or wanting to do this? I can't exactly find it but I remember a history expert on TikTok debunked a meme making fun of it saying only rich people and royalty did it, that both the boys and girls were ~ 5 years or less apart, and that they don't have kids until the late teens or early adulthood. IDK whos wrong, I'm just asking.
This has been asked here before. The beauty standard for women seems to vary from athletic to lithe to voluptuous to 'plump' (but never obese) based on region and period, while for men it is much more consistent. e.g. Socrates "What a disgrace it is for a man to grow old without ever seeing the beauty and strength of which his body is capable."
You may be better off asking your second question independently. I'm aware it's at best highly misleading, early puberty as we've had it is a recent (past two centuries) historic phenomenon and the aversion to prepubescent marriage and relations is not new and has been discussed before.
As to the age of Juliet specifically, though, that one is easier. She was never twelve. She was 13 in Shakespeare's telling, 16 in Brooke's, and 18 in in the original work by Porto.
Neither one is the case.
Regarding beauty standards of the medieval world, I have these two previous answers:
The idea that more weight = more attractive in lean times has a lot of truthiness, but is not necessarily the case, because society is simply more complicated than that. As looking at any medieval art will show you, the ideal woman was slender and small-busted.
I also have an answer to your second question:
That is, no, most of the time when an underaged girl was getting married, it was to an underaged boy for the purposes of securing one's property for the other. Adult men only married children if they needed to take their property and had no son to marry off, or, very very occasionally, if they were kings and needed to cement an alliance with a country that only had underage princesses and also had no sons of their own.