Calorie restriction

Calorie restriction, or caloric restriction (CR), is a dietary regimen that restricts calorie intake, where the baseline for the restriction varies, usually being the previous, unrestricted, intake of the subjects. CR when not associated with malnutrition, improves age related health and slows the aging process in some animals and fungi. CR is the only dietary intervention that has been documented to increase both the median and maximum lifespan in a variety of species, among them yeast, fish, rodents and dogs. There are currently ongoing studies on primates to show if CR works on primates, and even though they are showing positive indications it is still not certain that CR has a positive effect on longevity for primates and humans, due to the very lengthy time required for the completion of such lifespan studies. Calorie restriction in adult men and women is associated with beneficial metabolic, hormonal, and functional changes, but the precise amount of calorie intake or body fat mass associated with optimal health and maximum longevity in humans is not known. It is possible that moderate calorie restriction may be harmful in specific patient populations, such as lean persons who have minimal amounts of body fat. The effect of CR on IGF-1 serum levels seen in rodents has not yet been replicated in human trials. The life extension is varied, for mice and rats there is a 30-40% increase. Even though there has been research on CR for over 70 years the mechanism by which CR works is still not well understood.

Recent research has been in favour of the hypothesis that CR works by decreasing insulin levels and thereby upregulating autophagy, but CR affects many other health indicators and whether insulin is the main concern is still undecided.

Calorie restriction is a common measure found in several dietary regimens, including the Okinawa diet  and the CRON-diet.