So, in case you aren't from America, you might not know this: the food that is the cheapest also happens to be the food that is the least nutritious. Americans who are poor cannot afford fresh vegetables, fruit, meats and gym memberships. They can afford cheetos.
It is quite the spurious correlation to say that obesity causes hunger. Just wow.
Unprepared foods, in the US, are much cheaper than prepared foods.
A bag of Cheetos (16oz) is $5.
A pound of chicken legs is $2.
2 lbs of rice is $3.
I'd suggest you instead argue that low income people work multiple jobs and therefore have no time to cook. I've had this debate a lot before.
"I can't work out, I can't afford a gym! No, I'm not going to run around the park or join the YMCA!"
"I can't eat healthy, I can't afford it! No, I'm not going to buy a big bag of rice and black beans."
Before anyone comes at me: there are poor people and their struggles are real. I am 100% opposed to things like removing soda from food stamps.
https://fred.stlouisfed.org/series/APU0000706212
It's currently at $1.82/lb. Assuming that 30% of leg weight is inedible bone, it's more like $2.60 per pound of edible chicken.
"Normal" foods like rice and beans are dramatically cheaper than "junk" food.