The low caloric intake caused many to consider that this was similar to the observed increase in longevity seen when other species are given calorie restricted diets. The one thing not reported that could affect the results is the size of the people themselves. Each generation tends to be larger than the one before (in very recent history) and the elderly tend to "shrink" in size and be less active, which also decrease caloric needs.
Dan Buettner ("Blue Zones") replicated Leaf's work by trying to find areas where people live longer than usual. Significantly, none of Leaf's groups were found to be especailly long-lived any more. The Okinawans had already been known to have a large number of centenarians and there were reports of villages in Italy that also had many very old people. Besides Okinawa and Sicily, he found an area in Costa Rica and a group of Seventh-Day Adventists in Loma Linda, California (and reportedly, he also found a Greek island recently which he will undoubtedly document later).
A study in Italy to find the oldest citizens found, quite remarkably, that most had the unusual last name of Bau or were related to the Bau family. Their diet was fairly typical of the mediterranean region, but was very high in saturated fat, due to consumption of meat and especially cheese. It was discovered that they had a genetic mutation passed down from a Danish ancestor (whence the name Bau), which appeared to be protective against heart disease, causing them to outlive their neighbors who ate a similar diet. A pharmaceutical company jumped on this research and is trying to create a pill that mimics this effect.
One reason these people may live longer than average is by genetic self-selection. All of the areas studied are geographically separated "islands" (except the Loma Linda group, which are separated by choice). On islands, rare genes are more often expressed (which is why, for example, one finds unusually large or unusually small animals on remote islands). If the elderly are revered, then those who have elderly ancestors have elevated status and are more likely to have children, which increases the incidence of genes leading to improved longevity. These people may not be living longer because of anything they do, but because of choices made by the society in which they live.
The Tarahumara of Mexico and the Tendai Buddhist monks of Mt. Hiei near Nagano, Japan are reknowned for their being endurance athletes and there have been reports that their diets may be similar to the above. Next post, I'll try to address them. [Actually, there will undoubtedly be some unrelated personal posts first, then I'll get back to the matter at hand.]