Take $1, go into a grocery store, buy the maximum amount of calories you can for that dollar. You do NOT get those calories in the produce aisle, you get them in processed foods. I'm telling you, READ the book "Stuffed and Starved" Stuffed and Starved: The Hidden Battle for the World Food System: Raj Patel: 9781612191270: Amazon.com: Books
Or at the very least, watch the documentary on Netflix, A Place at the Table.
Look, poverty goes hand in hand with malnourishment. In developed countries, the poor and malnourished are obese. In third world countries, the poor and malnourished are underweight, it's the SAME THING. It's just in industrialized nations where cheap calories are easily accessible, the poor can fill their bellies with cheap sugary, fat and carby crap because we give them less than subsistence level amounts of food stamps and in impoverished countries they simply have nothing.