Caloric Restriction in non-obese people translates into less oxidative damage in muscle cells, according to a new study by Anthony Civitarese, Eric Ravussin, and colleagues (Pennington Biomedical Research Center). As oxidative damage has been linked to aging, this could explain how limiting calorie intake without malnutrition extends life span.
A calorie-restricted diet provides all the nutrients necessary for a healthy life but minimizes the energy (calories) supplied in the diet. This type of diet increases the life span of mice and delays the onset of age-related chronic diseases such as cancers, heart disease, and stroke in rodents. There are also hints that people who eat a calorie-restricted diet might live longer than those who overeat. In addition, calorie-restricted diets beneficially affect several biomarkers of aging, including decreased insulin sensitivity (a precursor to diabetes). But how might caloric restriction slow aging? A major factor in the age-related decline of bodily functions is the accumulation of "oxidative damage" in the body's proteins, fats, and DNA. Oxidantsin particular, chemicals called "free radicals"are produced when food is converted to energy by cellular structures called mitochondria. One theory for h ow caloric restriction slows aging is that it lowers free-radical production by inducing the formation of efficient mitochondria.
Civitarese and colleagues enrolled 36 healthy overweight but non-obese young people into their study. A third of them received 100% of their energy requirements in their diet; the caloric restriction (CR) group had their calorie intake reduced by 25%; and the caloric restriction plus exercise (CREX) group had their calorie intake reduced by 12.5% and their energy expenditure increased by 12.5%. The researchers found that a 25% caloric deficit for 6 months, achieved by diet alone or by diet plus exercise, decreased 24hr whole body energy expenditure (i.e. overall calories burned),
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