Low-Calorie Diet

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. Calorie restriction without malnutrition has been shown to improve age-related health and to slow the aging process in a wide range of animals and some fungi. CR is one of the few dietary interventions that have 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 to investigate whether CR works in nonhuman primates, and its effects on human health and metabolic parameters associated with CR in other species. The results so far are positive, but the studies are not yet complete, due to the long lifespan of the species.

Calorie restriction is a feature of several dietary regimens, including the Okinawa diet and the CRON-diet.

Although most studies conducted showed that these diets can improve longevity and health in the long term, the effects of calorie restriction on humans is still controversial. Some studies on humans revealed a number of benefits of calorie restriction but also major side effects such as loss of muscle mass, muscle strength and loss of bone. In the middle aged or elderly low body weight is associated with premature mortality from cardiovascular disease and cancers. Confounds to these studies exist but higher mortality rates make the view that human CR leads to increases in lifespan as robust as CR leads to in rodents questionable nonetheless. An expert on aging has voiced concern over his CR practicing colleague Mark Mattson saying “This guy has no reserves.”

The health concerns in the case of calorie restriction begin when an individual cuts off too many calories. Researchers have reported that “excessive calorie restriction causes malnutrition and can lead to anemia, muscle wasting, weakness, dizziness, lethargy, fatigue, nausea, diarrhea, constipation, gallstones, irritability and depression”. Although calorie restriction may have potential benefits for individuals, the majority of nutritionists agree that a diet that does not comprise enough calories for the individual’s body may lead to serious health problems.

Many specialists believe that calorie restriction can make individuals feel hungry all the time and this may lead to them getting obsessed with food which can easily become the cause of various eating disorders. Most commonly, individuals who are trying to lose weight quickly with the help of calorie restriction diets are at risk of developing anorexia nervosa, a type of eating disorder.

The effect of these diets on people who want to lose weight is controversial. Although calorie restriction may provide quick weight loss, several studies have shown that the body adjusts to the new diet in more or less half a year. Researchers argue that people who have little body fat should not use this method of losing weight but rather should exercise more because calorie restriction in this case can be harmful. The reason for this is that after the body’s fat reserves have been burned for energy, the proteins within muscle tissue will be consumed. In severe cases where individuals do not acknowledge the dangers they are exposing themselves to, they may suffer serious loss of the muscle mass.

Several studies conducted in this sense revealed that dieters who restricted calories for 12 months had lower muscle mass and a reduced capacity to perform exercise compared with those who lost similar amounts of weight from exercise alone. Another study concluded that individuals who lost weight with the help of the calorie restriction diets are more prone to develop a loss of bone at the level of hip and spine, the area most at risk for bone fractures. Some specialists however claim that minor mineral losses can be prevented with supplements of vitamin D and calcium.

It has also been noted that people who are willing to lose weight by following such diets put themselves at risk of developing cold sensitivity, menstrual irregularities and even infertility and hormonal changes. Moreover, recent studies attack the earlier studies that found that calorie restriction may improve memory and attention. A study published in 2007 in Rejuvenation Research magazine shows that there is no significant link between this diet and memory or attention problems. Excessive calorie restriction may lead to swelling in the individual’s legs and feet.

~ by superbowlnyc on January 30, 2011.

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