The stat comes from people reporting that they have felt hungry without having enough food to satiate their hunger. Totally makes sense at first pass.
But here is the rub, obesity is out of control in the US, and it is especially bad in poorer populations.
So now we have two conflicting stats: Poor people are food insecure while simultaneously being overweight...
The reconciliation is easy, when you are obese, you get hungry more and eat more. A 325lb average height male has to eat ~50% (!) more food per day than a healthy weight male of the same stature.
I know this is a bit of the stick in the spokes of the stat, but its blatantly obvious that America does not have a low income hunger problem, it has a low income obesity problem.