probably seen as a sign of laziness, lack of willpower, gluttony and being unhealthy. Thinness is prized as it's a sign of working out, eating right and not being seen as diabetes/walking heart attack. This is what fat is vllified as. Long ago fatness was a sign of strength, health and fertility as it meant being able to eat food which was rare long ago. Just how things change. Can also see it as us liking something that falls outside the norm. Something society is taught to hate and fear and liking it is seen as bad/weird. We're taught as a society to hate fat, to always be on a diet and that we should be horrified at the thought of fat people being sexy or having sex.