Those interested in the calorie-restricted lifestyle should be aware of the following potential issues:

List of disadvantages

			Physical effects
			Tissue loss The body's response to low dietary energy levels involves burning off any existing resources. The body's least important tissues are dispensed with first - but their absence can still have some side effects... Less fat Body fat is burned as fuel during CR's weight-loss phase. This results in reduced thermal and mechanical insulation - and depleted fuel reserves... Reduced thermal insulation Reduced body fat and decreased body temperature can make practitioners more sensitive to prolonged cold temperatures. As a result, unexpected, prolonged cold exposure can become more dangerous - such as after a car failure on the highway in winter. Also, reduced subcutaneous fat may increase the hazard represented by local heat and burns - by removing an insulating layer and exposing the more important and sensitive tissues beneath. Reduced mechanical insulation Less insulation due to fat results in external objects getting closer to your skeletal structure. This can result in tissue near the (smaller) contact point getting squashed. This can result for example, in discomfort in the buttocks while sitting on a hard surface. Similarly, collisions with external objects are less likely to be decelerated by a protective insulating layer - and are more likely to reach underlying tissues - such as bone. The result can be that the energy from a more rapid deceleration is concentrated in a smaller area - and there is a greater chance of breaking the skin and doing damage to underlying structures. Reduced energy reserves Fat deposits represent the body's primary energy reserves. These can be drastically depleted during CR. Energy is widely and abundantly available in the modern world - and that shows few signs of changing any time soon - but there are still a few cases where resource availability could cause problems. Being unexpectedly stuck on a boat, locked in a room or lost in a wilderness are all scenarios where resource reserves may be important. It is theorised that some "wasting" diseases may deplete energy reserves - by interfering with metabolism and making it harder to use dietary energy. Intestinal parasites might produce such an effect. It is also theorised that some flu-like disorders characterised by fevers may make energetic demands on the body which can be best met by existing fat reserves. Drained states and weakness can sometimes result if activities requiring stamina are performed for extended periods of time. Less muscle Muscle tissue is often burned as fuel during CR's weight-loss phase. This saves energy overall - since muscles need energy to maintain them. The result is often reduced strength and stamina... Reduced strength CR is likely to result in reduced muscle mass and lower strength. This could cause problems under circumstances where strength is needed. For example, strength can be needed when attempting to absorb a blow - from something like a falling heavy object - or when preventing damage from a fall onto the ground. Reduced stamina A combination of reduced muscle mass and lower stores of energy means that CR practitioners are likely to be unable to repeat exercises as many times - and lack stamina. This could cause problems under circumstances where stamina is needed - for example, if engaged in a chase. Less bone Reduced bone mineral density Weight loss is often accompanied by reduced bone mass - which is likely to place the practitioner at a somewhat greater risk of certain sorts of fracture. Smaller organs CR will often reduce the size of other bodily organs - besides muscle and fat tissue. Smaller organs of digestion The liver is involved in detoxifying the blood, and a smaller liver may be become overloaded more easily - under some conditions. Smaller brain components Though studies suggest brain size is not reduced in organisms doing adult-onset CR, one study of rhesus monkeys found parts of the brains of the CR'd individuals reduced in size. More study can be expected to clarify the existence of this effect. Smaller testicles One study of rats found their testicles shrank by 20% when they were on CR. More study can be expected to clarify the existence of this effect. The liver is involved in detoxifying the blood, and a smaller liver may be become overloaded more easily - under some conditions. A smaller pancreas is less able to secrete large volumes of insulin. This may result in reduced ability to tolerate large loads of glucose. The size of the stomach can limit how much food it is possible to eat at once. This could make brief, rapid refeeding more difficult. Cosmetic problems CR can affect the appearance of those who pursue it. This can affect how others regard practitioners and behave towards them... Reduced attractiveness Among women, a certain level of fat is widely regarded as sexually attractive. Some degree of fat on thighs, buttocks and breasts is believed to act as a signal of fertility. Similarly among men, a certain degree of muscular development is perceived as being indicative of health, freedom from disease, strength and stamina. As a result of their dietary practices, practitioners sometimes find some of their friends and family think they are "too thin". Percieved weakness Extremes of slenderness are sometimes associated with disease states. As a result of this, there is a link in the minds of many people between extreme slenderness and illness. Consequently some people may assume that because practitioners are thin they are also ill. Percieved lack of strength might also make practitioners targets for criminal elements of society who seek to take advantage of others weaknesses for their own benefit. Down-regulation of non-essential functions CR can interfere with bodily functions not of immediate relevance to survival... Reproductive problems Low energy intake can temporarily shut down reproductive function... Libido reduction More extreme CR can result in reduced interest in sexual activity - and reduced levels of desire. Menstrual irregularity A very low calorie intake can sometimes interfere with menstrual function in women - and can cause amenorrhea - a cessation of menstruation. Reduced fertility In rodents, CR appears to reduce fertility, reduces sperm motility, and increases the proportion of sperm that are abnormal. 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 initiate CR until after having (and weaning) their offspring. Those already practicing CR should seriously consider increasing their calorie intake if contemplating reproductive activity. Slower growth Growth processes are often suppressed in CR'd organisms. They are rarely urgently necessary - and can demand resources... Slower wound healing Wounds heal more slowly among CR practitioners. This could be a complicating factor if facing any major operations, and may increase risk after traumatic injury. Tissue adaptation Some tissues respond with growth to demands made by usage. This can happen with muscles, bones and teeth. Muscles normally grow in strength when demands are made on them; Bones increase in density and strength when forces are applied to them; However CR makes growth processes more difficult - making these processes less likely to happen. Thermoregulation Heating the body can be expensive. CR turns down the heat... Cold extremities CR lowers the core body temperature of practitioners. A reduced heating budget also seems to make it more likely for the body to go into a mode where circulation in the extremities is restricted to keep warm blood near the core of the body. This can leads to discomfort in the extremities, loss of feeling and motor competence - and in extreme cases - cell death due to asphyxiation, or frostbite.
			Lifestyle effects
			Psychological effects CR can influence things such as mental outlook and emotional function... Psychological issues CR interferes with a basic drive - the consumption of food. This can have psychological repercussions... Hunger Hunger and craving for food are widely regarded as unpleasant sensations. However for some practitioners, they are a regular part of their practice of CR. Hunger - and having your thoughts constantly returning to the subject of food - can represent distractions that interfere with other activities in a debilitating manner. Obsession To a certain extent, a preoccupation with food is healthy - given its significance to health and well being. The optimal diet is certainly an interesting and important subject - and CR is a powerful instrument for postitive change that many individuals should understand and explore. However, the fact that many CR'd individuals are constantly having their thoughts dragged back to food by hunger can - contribute to them spending more time and energy thinking about food and diet than perhaps is rational or healthy. Mood changes Some have reported that their mood alters in a negative way when their energy intake goes too low. The reported symptoms appear to be rather similar to depression. Others have reported feelings of detachment; a lack of emotion. Studies of the effects of starvation have reported dramatic increases in preoccupation with food, difficulty in concentrating - and a range of emotional, social and sexual changes in those deprived of a substantial share of their normal food intake for extended periods. 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 socialising 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; Such factors can work to divide and isolate family members - unless active steps are taken to combat their effects. Social events with food Many other types of social event also often involve eating: Eating out at restaurants and bars; Hosts often offer food to visitors; Workplace lunches; Food and socialising are often intertwined; and not eating - or following unorthodox diets - can interfere with some aspects of a normal social life. Resource management CR can affect how practitioners allocate their resources... Time and money