There are two kinds of fat: fat gained by a person who enjoys life to the fullest (particularly food and leisure) and fat gained from despair. The fat looks different. I once knew an opera singer who was 40 pounds overweight: she was gorgeous, vibrant almost perfect. I envied her immensely.

But I see other people carrying extra weight around and I can tell they’ve gained it because they just didn’t have anything better to do than eat. The fat is lumpy in most cases and unevenly distributed over the body. That’s why I am ambivalent about the fat acceptance movement, I just get the feeling if they were happier they'd lose it.

Good fat
evenly distributed
smooth surface
supported by mild muscle tone
enhances shape of figure
dose not jiggle very much
fits the way the person moves
even circulation

Bad fat
unevenly distributed
inhibits movement
poor, uneven circulation

I think that Tem42 (below) is right about it being partially subjective.