When I was a kid, "fat" was definitely used as a negative word. It was what you called someone, including yourself, when you didn't like them. Maybe you just wanted to hurt their feelings. Maybe you were feeling bad about yourself and wanted to be hateful. You were calling our their failure to meet the beauty standard you'd been indoctrinated with through the current media culture, which said (destructively), "Fat = Worth Less."
The beauty standard is much more variable than we recognize. It's a way to categorize people and their worth, dependent on the current social landscape. It validates the power of those already in power. It's almost always simply the most difficult thing for a person to achieve. Beauty is rare. Beauty is expensive.
When everyone was a peasant farmer, only rich rulers could afford to lay around and gorge themselves… so beauty was found in being fat. When we all started organizing ourselves into cities and doing more desk jobs and only had to walk a few feet from our front door to our cars and processed foods were cheaper than fresh foods, we all got fat… so beauty became being skinny. When everyone began finding themselves somewhere between slow moving fat people and emaciated calorie counters, the richest of us figured out you could pay for a private gym membership and a sergeant-like, order-barking personal trainer and purchase ready-prep, quick-cook, diced and sliced "homemade" fresh meals THROUGH THE MAIL.. so beauty became athletic.
But if beauty really only exists in the eye of the beholder, couldn't we change our worth by changing the beholder? What about when the beholder is YOU?
Could fat become just a descriptor of cells in the body? Could there be a lot of other things that just describe how you are, rather than how much you are worth? And if your worth no longer comes from how you are, where will you find it?