On a base level; they consume more (medical resources, food, waste disposal, circus fabric) and contribute less (work, labor, beauty.) It isn't cultural it's basic group mentality. No one would want them in their group of they could choose.  If a vote came up to send everyone with a BMI over 30 to Mississippi, Alabama, Louisiana, and Texas.  And extend the border wall around them, I'd vote yes.  Those with a BMI between 25 and 30 may remain but have to pay a fat tax. If they go over 30 they get shipped south.