The approach, called calorie restriction, involves eating about 30 percent fewer calories than normal while still getting adequate amounts of vitamins, minerals and other nutrients. Aside from direct genetic manipulation, calorie restriction is the only strategy known to extend life consistently in a variety of animal species, a report of study in a laboratory at the Wisconsin National Primate Research Center, highlighted by Michael Mason in the New York Times.
Calorie restriction or Caloric restriction (CR) is the practice of limiting dietary energy intake in the hope that it will improve health and retard aging. In human subjects, CR has been shown to lower cholesterol, fasting glucose, and blood pressure. Some consider these to be biomarkers of aging, since there is a correlation between these markers and risk of diseases associated with aging.
Except for houseflies (below), animal species tested with CR so far, including primates, rats, mice, spiders, Drosophila, C. elegans and rotifers, have shown lifespan extension. CR is the only known dietary measure capable of extending maximum lifespan, as opposed to average lifespan.
In CR energy intake is minimized, but sufficient quantities of vitamins, minerals and other important nutrients must be eaten. To emphasize the difference between CR and mere “FR” (food restriction), CR is often referred to by a plethora of other names such as CRON or CRAN (calorie restriction with optimal/adequate nutrition), or the “high-low diet” (high in all nutrients aside from calories, in which it is “low”). Other names for the diet emphasize the goal of the diet, such as CRL (calorie restriction for longevity), or simply The Longevity Diet, as in a recently published book by that name.
Ageing or aging is the process of becoming older. This traditional definition was recently challenged in the new “Handbook of the Biology of Aging” (Academic Press, 2006), where ageing was specifically defined as the process of system’s deterioration with time, thus allowing for existence of non-ageing systems (when “old is as good as new”), and anti-ageing interventions (when accumulated damage is repaired).
The concept of “successful ageing”, as Strawbridge et al. (2002), have pointed out, can be traced back to the 1950s, but was popularised in an article by Rowe and Kahn (1987). These authors believed that former research into ageing had exaggerated the extent to which health disabilities, such as diabetes or osteoporosis, could be attributed exclusively to age, and also criticised former research in gerontology for exaggerating the homogeneity of samples of elderly people. In a subsequent publication, Rowe and Kahn (1997) criticise earlier work for making what, to them, is an over-simplistic distinction between pathologic and non-pathologic ageing, and distinguish between “normal ageing” (marked by high risk of illness), and “successful ageing” (marked by low risk of disability and high cognitive and physical functioning).
They define “successful ageing” more specifically as consisting of three components:
1. Low probability of disease or disability;
2. high cognitive and physical function capacity;
3. active engagement with life.
Researchers at New York’s Mount Sinai School of Medicine found that compared to monkeys fed a normal diet, squirrel monkeys on a life-long calorie-restrictive diet were less likely to develop Alzheimer’s-like changes in their brains.