One of the first cases of hacking the bodies biology for longevity was the story of Luigi Cornaro. Luigi was a venetian nobleman born in 1467, he lived a glutinous life of excessive eating and drinking, and by age 35 the venetian was plagued by gastrointestinal issues and an insistent fever. Eager to avoid a premature death, he figured that his excessive habits were to blame, and pledged himself to a life of constraint. His new diet included only 12 ounces of food a week (eggs, bread, soup etc.), and 14 ounces of red wine a week. Within a few weeks Luigi’s afflictions have waned and he lived to the ripe old age of 98, which was a whopping double the average lifespan of that time. Despite his success, it was a few hundred years until anyone decided to investigate the importance of the diet on longevity.
In the 1930s, a group in the United States of America decided to take a look at how the starvation caused by the Great depression affected growth rates. By feeding mice a restricted diet the researchers hypothesized that the lifespan of the mice would be severely stunted. Much to their shock, they found that the mice lived longer! McCay the lead researchers proposed that the basis of this life extension was the slowing of growth. This theory remained until the 1960s, when Berg and Simms proposed that the reduction of body fat content was the cause for life extension, helping to promote the demonising of dietary fats within the media of the time. Other hypotheses have sprung up since then, but still, the underlying biological mechanism as to why calorie restriction seems to ubiquitously elongate life remains a mystery.
In a more recent study investigating the effects of dietary restriction on 41 different strains of mice, both male and female, the results showed something to the contrary. The mice control group were fed without constraint (ad libitum), whereas the calorie restricted group were fed on a diet containing 40% less calories than the control. It was discovered that calorie restriction extends lifespan in only a small subset of mice strains. Not only this, but it was also found that keeping the calorie count to a minimum actually shortens the lifespan in an even larger subset. This could suggest that calorie restriction isn’t universally beneficial.
Two experiments, which began in the late 1980s, but have recently yielded results, tested whether caloric restriction improved health and survival in rhesus monkeys. One hosted by the University of Wisconsin, where scientists studied 76 adult monkeys (Jul 2009 news). The other, from NIA, included 121 monkeys aged 1 to 23 (Aug 2012 news). Both studies put half the monkeys on a CR diet. At the NIA, some animals started the diet when they were young, and some when they were older. There were some discrepencies and confounding issues between the control groups used in the studies. However, taken together, the data suggest that CR does in fact extend lifespan in monkeys.
Stephen Ginsberg, New York University Medical Center (who was not involved in the work)
This confirms what a lot of researchers have thought—that diet makes aging malleable in a nonhuman primate. It’s quite significant—the implication is that it’s translatable to humans.