I would say my biggest insecurity is my height. I am not a midget by any means, but I will never be able to pass as 6 foot tall man. Does not help that I also live in one of the States with the highest average height. Not uncommon for women to be taller than I am. Usually at a grocery store line I look to see if any other men are shorter than I am, and 9 times out of 10 there isn't one. The rare instance the other man is usually Asian or Hispanic, lol.
Sometimes I wish I had broader shoulders too. My father's side is very neotenous for European origins. Sadly, I inherited their body type. Ironically my mother's side is more traditional in European body appearances. Growing up I realized my mother has somewhat unusual tastes in men compared to other women. She likes the smaller more feminine looking men. When my mother had a crush on my father, he tried to pass her on to a 6+ tall well-built man who had a huge crush on her himself, but she ended up friend zoning him and my father decided to finally give her a chance, lol.
Besides those two things I do not really have any other body insecurities, besides getting older. I do feel like the early 30s is the last "hurrah" for looking young. Even for men, I've read studies that men's appearances tend to dip past the age of 36 or something. We can rely on other things to attract mates, but the 40s seems to be when people really start falling apart, lol.
I like my facial features and thick hair; I usually get complimented about them by others. Sometimes I wish I had more of the "hunter eyes" look but can't do anything about that. Or maybe I can, but I doubt I'd ever go the plastic surgery route, lol. Double eyelid surgery is popular in Asia, even among men... yet I suspect many European men would like narrower eyes... lol.. the grass is always greener on the other side. Lol.