Could be a mating strategy. A girl could be a 4 and push woman to get fat in the hope that she will become relatively more attractive. This woman looks too old for that, but maybe she has a daughter who isn't that attractive. Also fats are less able to have kids both because they are less attractive and medical issues so you can end up out producing them. Or economically, push people to get fat (while even being paid for it) and they'll be less able to work and attractive people who are preferable to hire will be in lower supply thus it'll be easier to get better jobs.