At in the last episodes of Yu Yu Hakusho, when Yusuke met the Raizen's subordinates, they explained that Raizen stopped using humans as food, but his subordinates didn't. Moreover, the other two Makai Kings (Yomi and Mukuro) still use humans as the main food source. So it's possible to say that all their subordinates and maybe others youkai do that.
However since it's difficult to open a gate between ningenkai (human world) and makai (demon world), given the difficulty Sensui had. Was there an explanation to how could all the Class A/S youkai get so many humans?