Why are poor kids fatter than rich kids?

It used to be that being fat indicated wealth. You could afford a lot of food, and you didn't work it off the next day.

Now, it is related to poverty and, presumably, the kind of diet poor people have.

The researchers found obesity most common in children living in neighborhoods with the least-educated females, most single-parent households, lowest median household income, highest proportion of non-white residents, and fewest homes owned. Together, these five socioeconomic factors accounted for 24 percent of the variability in childhood obesity rates across neighborhoods.

 So these 5 environmental factors account for 24% of the variability among neighborhoods. While I believe that much of obesity is caused by genetic factors, that would not explain variability among neighborhoods, unless you believe that neighborhoods are sorted by genes. (Okay, to some extent they are, such as many more Somalis living in this neighborhood and many more Vietnamese or Samoans in that one, but that's irrelevant here.)

That leaves 3/4 of the variability to be due to what? If it's not genes, and it's not education, single-parenthood, income, race, or home ownership, what else can it be? Which commercials are shown on the TV shows they watch? What car they drive? Access to routine medical care? Number of meals eaten out of the home divided by the cost of the meal? Number of fast-food restaurants per 10,000 population? That's a lot of variability to account for when you have already used the best ones.