Get a load of this. Fasting for two days protects healthy cells against chemotherapy, according to a study appearing online the week of Mar. 31 in PNAS Early Edition. Mice given a high dose of chemotherapy after fasting continued to thrive. The same dose killed half the normally fed mice and caused lasting weight and energy loss in the survivors. ... The idea for the study came from the Longo group’s previous research on aging in cellular systems, primarily lowly baker’s yeast. About five years ago, Longo was thinking about the genetic pathways involved both in the starvation response and in mammalian tumors. When the pathways are silenced, starved cells go into what Longo calls a maintenance mode characterized by extreme resistance to stresses. In essence the cells are waiting out the lean period, much like hibernating animals. But tumors by definition disobey orders to stop growing because the same genetic pathways are stuck in an “on” mode. That could mean, Longo realized, that the starvation response might differentiate normal and cancer cells by their stress resistance, and that healthy cells might withstand much more chemotherapy than cancer cells. The shield for healthy cells does not need to be perfect,...