Of all the methods currently used to extend healthy lifespan, calorie restriction (CR) is probably the most well researched. The idea behind CR is simple: Eat less, age less. While this correlation has been demonstrated in species as diverse as yeast, rodents and fruit flies, what causes the phenomenon has remained a mystery to scientists for decades.

The first serious study of CR was conducted by Clive McCay and Mary Crowell of Cornell University in 1934. They observed that rats fed a calorie restricted diet had lifespans up to twice as long as control rats. These studies were elaborated upon by a series of mouse studies conducted by Dr. Roy Walford in the '80s. Walford observed that mice on CR not only lived longer than control mice, but exhibited healthier appearances and activity levels, and delayed onset of age-related diseases.

Experiments in primates are much more recent. Rhesus monkey studies conducted by the University of Wisconsin and the National Institute on Ageing have yielded promising results. The UofW project studied the effects of CR by comparing the results of a CR test group with those of a control group whose eating was unrestricted, and mimicked the macronutrient content of a modern American high-sugar high-fat diet. The NIA study compared their CR monkeys to a control group that was fed a much more balanced, limited diet than that of the UofW study. The results, unsurprisingly, are that CR has healthy benefits in both groups, but that these benefits are much more pronounced in UofW study than in the NIA study. This provides evidence that not only is CR effective at slowing ageing and the onset of age-related diseases, but also that the reverse is true: Overeating actually speeds up the ageing process and causes the development of age-related diseases earlier in life.

Research on CR's effects on humans is in much earlier stages, but is already showing promising results. The CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy) study being conducted by Washington University has demonstrated exciting improvements in a wide range of biomarkers realated to health and ageing including: Reduced insulin resistance, lower LDL cholesterol and less damage to DNA from oxidation.

For all these reasons and more, I have decided to practice CR in my personal life over the past 2 years, and I have made substantial improvements in my overall health. In an upcoming article I intend to create a practical guide for anyone wanting to start a CR regimen of their own, in which I will provide some tips and tricks from my own experiences that will hopefully help readers overcome the difficulties associated with this challenging dieting regimen.C