I'm sure it's written somewhere, tucked away, that keeping prisoners, captives or other types of incarcerated criminals and POW's on a bare minimum diet (2000 calories maybe?) sets a certain sort of tone to either get a desired effect out of those locked away or make them vulnerable to questioning if not reduced to only having enough energy for one short burst of energy in the event of a physical altercation.

Of course this has to be against all sorts of laws and conventions so I doubt it's publicly traded knowledge but the whole idea reminds me of the grey area psychologists and interrogation specialists tend to talk about when topics like water boarding and other torture / effective interrogation methods are questioned.