If I could I'd frame your stretch marks
You only get them two ways
Giving birth or dropping weight
Either way, serious pain
~Propoganda, Framed Stretch Marks
If you're an adult female of any size or shape, you probably hate your body. If you are an adult male, there is also a good chance you have issues with your body. Some have a mild distaste for their image in the mirror and might even laugh at their flaws, but others - many others - have serious issues with the way they look.
There is a name for this disorder. It's called body dysmorphic disorder. Though I'm not a fan over our obsession with over diagnosis, this disorder is to me something we need to categorize so we can kill it. Whether or not BDD is a legit mental condition I do not know, but let's just use that as our junk drawer term here for anyone who struggles with body image (read: most people).
How did we get here? Why are so many people convinced they're fat and ugly? Well, for one, our media has put forth airbrushed images of unrealistically skinny women and dudes who magically have no body hair who look like Greek gods. Further, the statistics state that most people (sadly, including Christ-followers) have looked at or continue to look at porn, which gives a completely unrealistic view of the body and healthy sexuality. If you take these two aspects away, there are other mental health factors, histories of abuse, etc. that could come into play.