New York dietitian Ayoob figured that Kunis was already at the low end of the normal range on the body mass index, or BMI, when she began training for the role, but afterward she dropped far below the miminum of 18.5.
"She would not be allowed to walk a runway in Spain," he said.
But, he said, there's no question that dancers sink to those levels.
"Their whole world is about deprivation and suffering," he said. "It's a very mascochistic lifestyle."
One that Kunis was apparently happy to abandon. She told E! that it took her only five days to put the weight back on.