As long as they're getting enough nutrients than I guess we couldn't say its bad for them per se, but at the same time, I give little credit to the theory that they will live longer. the above post made a good point-- these animal studies started out from birth and their metabolisms never had to adjust to a lower level of eating, they simply always ate that way. The other thing, appetite is a brain chemistry function, and your body is self-regulating. Why would our bodies be telling us we are hungry if its better for us to not eat? Human beings are evolutionary creatures like any others so why would we have genes that give us this brain chemistry function? If human being survived better (I.E. LONGER) on lower calories, we would not have this mechanism. It could be argued that people don't reprodice after a certain age, like 45, or so, and therefore no lifespan-increasing genes would matter after that age (because evolution is the direct result of which species can reproduce successfully and survive to create the next generation) but that would only be the case for females. Males can make a kid much older. and maybe there was some 72 yr old neanderthal still having kids way back when. I don't know. Just, instinctively, something tells me this deprivation diet isn't right. Our bodies are like they are for a reason-- they are most efficient this way, and they survived best this way , and our hunger mechanism is just as much a part of our physical bodies as our hands and eyelashes.