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In 1934, Mary Crowell and Clive McCay of Cornell University observed that laboratory rats fed a severely reduced calorie diet while maintaining micronutrient levels resulted in life spans of up to twice as long as otherwise expected. These findings were explored in detail by a series of experiments with mice conducted by Roy Walford and his student Richard Weindruch. In 1986, Weindruch reported that restricting the calorie intake of laboratory mice proportionally increased their life span compared to a group of mice with a normal diet. The calorie-restricted mice also maintained youthful appearances and activity levels longer and showed delays in age-related diseases. The results of the many experiments by Walford and Weindruch were summarized in their book The Retardation of Aging and Disease by Dietary Restriction (1988) (ISBN 0-398-05496-7). The findings have since been accepted and generalized to a range of other animals. Researchers are investigating the possibility of parallel physiological links in non-human and human primates. In the meantime, many people have independently adopted the practice of calorie restriction in some form. Currently there are 2 ongoing randomized control studies on the effects of CR in non-human primates: the Wisconsin National Primate Research Center and the National Institute on Aging CR monkey studies. In 1989, scientists at University of Wisconsin started a study involving 46 adult male and 30 female rhesus monkeys.[1][3] The National Institute on Aging CR monkeys study, started in 1987, involves 60 male and 60 female rhesus monkeys. Monkeys in both studies have been randomized with a 1:1 ratio to 30% CR or to a control diet. Results are being periodically published. A group of scientists at Washington University in St.Louis have studied long-term physiologic, metabolic and molecular effects of CR in a small group of healthy lean men and women.[6] In May 2007 a multi-center clinical trial called the CALERIE ( Comprehensive Assessment of the Long-term Effects of Reducing Energy Intake) study was begun, to examine the effect of 2 years of sustained 25% CR on: a) slowing aging as assessed by proxy indicators and b) protecting against age-related disease processes. 220 healthy volunteers across 3 sites (Tufts University, Pennington Biomedical Research Center, and Washington University School of Medicine) were recruited.[7] A study at UCSF called "CRONA" was started in December 2010, and studied 28 long-term CR practitioners over a few months.[8] The study was completed on September 20, 2011.[9] As of August 2012 the results had not yet been published. |
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