The commissary markup is absolutely true, but "deliberately underfed" is as far as I can tell, completely untrue. Most states actually have calorie minimum rules. Arkansas is 2300 per day. Kentucky 2400 per day. Both states mandate annual menu reviews by a third-party dietician. New York state's guideline is 2800 per day + 90g protein. California 2500 per day. The Federal Bureau of Prisons facilities additionally states there are to be at least 3 meals per day, two of them hot, and no more than 14 hours between dinner and breakfast.
These are all right within the USDA's general population daily calorie guidance of 2-3 thousand per day for males.
It's possible that some of this is down to the "Prison" vs "Jail" distinction?
But I can't source what I said.
What I can source is that prisoners largely report going hungry. That's a completely different problem though.
I cannot remove or edit my comment. Thank you for the push back.