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Risks

Along with all its demonstrated and potential benefits, calorie restriction may result in a range of other effects.
  • appearance changes -- CR-induced weight loss can affect the appearance ofthose who pursue it. In the overweight, these changes may be perceived positively -- but in others, negative perceptions may arise.
  • appearance changes -- CR-induced weight loss can affect the appearance ofthose who pursue it. In the overweight, these changes may be perceived positively -- but in others, negative perceptions may arise.
  • bone health -- while evidence suggests that CR may support long-term skeletal health, weight loss is often accompanied by reduced bone mass. Work with your physician, especially an endocrinologist, to monitor your bone mass and markers of bone formation.
  • cold sensitivity -- reduced body fat and decreased body temperature can make practitioners more sensitive to cold temperatures, while perhaps decreasing their sensitivity to extreme heat, and thus being a boon in summer.
  • children, adolescents, and young adults (under approx 21) should be advised against starting CR. Physical growth may be impaired by calorie restriction, as observed in lab animals. In addition, mental development and physical changes to the brain take place in late adolescence and early adulthood that could be negatively affected by calorie restriction. For this group, the best advice is to follow a normal (non-CR) diet until reaching early twenties.
  • hunger (both psychological and physical effects), cravings, or food obsession -- thoughts about food sometimes increase while practicing CR. For some, this may interfere with other aspects of their life. On the other hand. Many people come to welcome hunger, knowing that the hunger hormones. ghrelin and orexin are good for the brain and the heart.
  • menstrual irregularity -- dramatic weight loss can sometimes interfere with reproductive function in women. Women planning to get pregnant soon, should not begin CR until after having (and weaning) their baby.
  • pregnancy -- low BMI is widely regarded as a risk factor in pregnancy. It can result in ovulatory dysfunction and thus infertility. Underweight mothers have higher levels of preterm delivery - and more low birth-weight infants. Women planning to get pregnant soon, should not begin CR until after having (and weaning) their baby.
  • decreased testosterone Testosterone production often reduces at the beginning of CR practice. The beauty of the process is that the capability of producing this and other homrmones is preserved, so as calorie restrictors age, they become more likely to have higher levels of many hormones than their peers.
  • rapid weight loss (greater than 1 - 2 lbs/wk) -- may do more harm than good, as noted in animal studies. We recommend changing your diet gradually, focusing at first on changing the quality of your diet: many people find that improving their diets by replacing low-nutrition, high-Calorie foods (such as sugar, gflours, and high-saturated-fat) with high-nutrition, low-Calorie foods (notably vegetables and fruit to a lesser degree) will lead to some weight loss even without any attempt to reduce Calories. Once your overall diet has improved, allow our body to take as long as it needs to reach your stable weight or calorie target.
Synergistic interactions -- i.e. the combination of several CR effects

Lifestyle and Personal Impacts
Social Issues. Eating food is often a social phenomenon. CR can sometimes interfere with conventional social practices...
  • Family meals -- Eating is often a communal activity, and a time for socializing with members of the family. CR can present some problems in this area.
  • Some CR practitioners try to eat less frequently than is usual
  • CR diets may not be suitable for all family members
  • The quality of the communal time together is just as great if the CR practitioner is drinking lemon tea or eating dinner.
  • The variety of diets being catered to at a given meal can be a challenge but also an opportunity to teach children the importance of valuing health and of preparing and serving the most healthful nmeal to each family member. This can be the occasion to welcome the children's help -- teaching them about food preparation, nutritiom, and nurturing. The whole family can learn a lot together.
Social events with food -- Many other types of social event also often involve eating:
  • Restaurants and bars
  • Parties, where hosts often offer food to visitors
  • Workplace lunches
  • Holiday season
Food and socializing are often intertwined. Some people feel that not eating - or following unorthodox diets - can interfere with some aspects of a normal social life. Many others believe that when people get together for a social occasion, it is because they want to be together. Precisely what they are or are not eating takes a back seat to enjoying each others' company.

Time and Money
CR can be both a low-cost and relatively time-efficient regimen. For example: use frozen veggies or prepackaged salads; go for low-fat protein (turkey, canned fish, egg whites, soy and other meat substitutes or non-fat yogurt); add a dash of olive oil or a few raw almonds for fat; have an apple or orange for dessert; and, finally, take a generic multi-vitamin to make up for any deficiencies. However, achieving "optimal nutrition" can be time-consuming and expensive. Time:
  • preparing meals (more than they would otherwise do)
  • swapping notes with other practitioners over the Internet
  • educating themselves about how best to practice CR
  • monitoring their health
  • seeking out a variety of foods and nutrients
  • growing their own food
  • On the other hand, what is more important than actively living intentionally?
Money -- the health benefits suggest that CR should save on medical bills in the long run. However, it can involve expense on:
  • eating high quality foodstuffs
  • supplements
  • health monitoring equipment
  • consulting with physicians and/or extensive testing (many health plans may refuse to pay for certain tests in healthy individuals)
  • We must all be responsible in how we allocate our resources. A better investment than our own health and that of our loved ones would be hard to find.
CR Psychology
CR represents a dramatic change in diet. This can attract people attracted to the extreme, who may push the limits of safe or healthy CR practice. Some anecdotal reports of CR-induced psychological disturbances, including anorexia, bingeing, excessive food thoughts and fantasies. These have not been shown in peer-reviewed publications

In fact, extensive scientific evidence suggests that CR may effectively slow aging, reduce the incidence of disease, and prolong life.

Additional information
More information on specific topics can be mined from the Mailing Lists (search the archives). Use the descriptions above to narrow your search. Various books by Walford are also excellent resources. Notes:(1) CR means a reduction in intake of calories only. Just eating less food -- smaller portions of the food you typically eat -- will likely lead to malnutrition, rather than enhanced health. It's important to adjust your diet to ensure that intake of essential nutrients is maintained. Poorly-designed low-calorie diets are often low in calcium, zinc, iron, essential fatty acids, and protein. Fortunately, most people who practice CR find it quite easy to maintain proper nutrition for their age, sex, personal physiology and active lifestyle. The USRDA/DRI and Scientific American's New Food Pyramid may be used as a guide. Likewise, "yo-yo" dieting or "weight cycling" is not CR, but a far-too-common result of quick weight-loss diets. Some evidence suggests that yo-yo dieting may eliminate the beneficial effects of CR, or even be detrimental to health. If you find even minimal calorie restriction difficult, it is better to follow a healthy, non-CR diet.(2) Remember: despite the huge health/longevity improvements that CR potentially holds for humans it remains relatively "uncharted territory." Long-term physical and psychological effects are unknown. A CR lifestyle can involve (or necessitate, depending on the level of calorie reduction one wishes to pursue) carefully tracking calories, nutrients and physiological parameters (hormone levels, bone health, muscle/fat mass, etc.). As always, consult your doctor before making any dietary changes.