Sure, when the Japanese and German soldiers and civilians started to starve, the prisoners didn't get fed well either.

However, there are thousands of pre-food-shortage eyewitness accounts of prisoners being worked like slaves and fed far less than what they needed to stay healthy. Both the Germans and the Japanese did it. The Russians did as well, with their German captives.

The prisoners in question were being intentionally held right at the edge, where they could still work, but most did not have enough energy to seriously consider escape or resistance.