If the money is low and they really are poor (as opposed to scammed out playing basketball or running with gangs) then this would be expected.
If you eat cheap, you eat carbs.
Potatoes, grains, noodles.
Also (by government standards) bodybuilders are “obese.”
I don’t think it’s eating cheap as much as it is eating “lazy” - ie, convenience food full of carbs, fat, and sodium.