CRON, or Calorie Restriction with Optimum Nutrition, is an acronym given to a diet or lifestyle by Dr. Roy Walford, UCLA professor and doctor of pathology. Walford began his experiments in the 1960s and, along with Dr Richard Weindruch of the University of Wisconsin and Dr Stephen Spindler from the University of California, concluded that calorie restriction is the only proven, research-backed technique known to extend lifespan and "healthy years."
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The goal of CRON is to eat fewer calories and consume adequate vitamins and minerals in food. Nutrient-dense vegetables replace calorie-sparse foods such as simple sugars and flours. Vegetables contain the highest content of nutrients for the calorie content, and along with fruits provide the basic carbohydrates needed. Protein, ideally low fat, and mono-unsaturated fat choices are selected carefully. After the diet quality is improved, the calorie reduction is done slowly, ideally over one to two years, recommends Dr. Walford.
Dr Walford's human study in 1990, the "Biosphere Project," found data supporting improved biomarkers of aging, such as cholesterol and blood pressure. Short-term benefits as reported by CRON dieter testimonials occur within a few weeks, and include fewer colds, fewer headaches, less acne, less required sleep and greater energy. Based on empirical evidence from repeated calorie-restriction studies, the National Institute on Aging lists several long-term benefits. They include decreases in cancer, diabetes, heart disease and auto-immune disease.
The CR Society points out that calorie restriction can sometimes interfere with conventional social practices. As CRON practitioners tend to eat less frequently, and eat different kinds of foods, it can lead to isolation. Family meals, parties, holidays and dining out can become potential sources of conflict. Time and money can also become more demanding, as it takes longer to shop for and prepare healthy meals, and extra money for high quality foods and produce.
Calorie restriction may result in a wide range of negative side effects, according to the CR Society. Physical appearance could become unattractive if the dieter gets too "skinny." Other negative side effects include reduced bone mass; cold sensitivity from decreased body fat and temperature; loss of "cushioning" with bony joints and discomfort sitting on hard surfaces; hunger, cravings, and food obsessions; menstrual irregularity with more difficulty conceiving; and loss of strength from decreased muscle mass.
The National Institute on Aging claims that calorie restriction remains the only nongenetic intervention that extends the life-span in mammals, and delays or slows many age-related processes. MIT professor Leonard Guarente discovered in 2000 that calorie restriction activated the silenced information regulator SIR2 gene, which has the ability to slow aging during a low-calorie diet. Dr. Bradley Wilcox of the Pacific Health Research Institute studied data from 1,900 men collected over 36 years, and concluded that a reduced-calorie diet promotes longevity.