It is unlikely that an eating disorder will result from a single cause. Much more likely is a combination of many factors, events, feelings or pressures that lead to the sufferer feeling unable to cope, precipitating this maladaptive coping mechanism. Examples of such factors include low self-esteem, problematic family relationships, trouble with friends, the death of someone special, difficulties at school, lack of confidence, and sexual or emotional abuse.

Often people with eating disorders say that the eating disorder is the only way they feel they can stay in control of their life, but as time goes on it becomes evident that the eating disorder itself is controlling them. It is common amongst those with eating disorders to experience feelings of despair and shame. They may also identify with feelings of failure or lack of control due to inability to overcome these feelings about food alone.

An Eating Disorder is an illness that permeates all aspects of the sufferer's life. It is a serious health condition that can be both physically and emotionally destructive. People with eating disorders need to seek professional help as soon as possible, as early diagnosis and intervention may enhance recovery. Eating disorders can become chronic, debilitating, and even life-threatening conditions.

Anorexia Nervosa
'Anorexia nervosa' literally means 'loss of appetite for nervous reasons' but this is misleading, as in most cases the appetite of the sufferer is undiminished but is systematically unsatisfied. Individuals with anorexia nervosa are unwilling or unable to maintain a body weight that is normal or expected for their age and height (most clinicians use 85% of normal weight as a guide). The disorder is characterised by a fear of gaining weight, self-starvation, and a distorted view of body image. Concerns and perceptions about their weight have an extremely powerful influence and impact on their self-evaluation and anorectics typically restrict the amount eaten and drunk, often to a dangerous level. Exercise may be used to burn off what are perceived to be excess calories. The seriousness of the weight loss and its physical effects are minimised or denied.

Diagnostic criteria of anorexia nervosa include two subtypes of the disorder that describe two distinct behavioural patterns. Individuals with the Restricting Type maintain their low body weight purely by restricting food intake and increased activity. Those with the Binge-Eating/Purging Type usually restrict their food intake but also regularly engage in binge eating and/or purging behaviours.

Initially the sufferer focuses on food in an attempt to cope with life; it becomes a way of demonstrating control over body weight and shape. Ultimately, however, the disorder itself takes control and the chemical changes in the body affect the brain and distort thinking, making it almost impossible to make rational decisions about food. People who suffer from anorexia often have low self-esteem and a tremendous need to control their surroundings and emotions. As the illness progresses, the sufferer will experience the exhaustion of starvation. Occasionally people die from the effects of anorexia, especially if it is untreated.

Bulimia Nervosa
It was only in 1979 that bulimia nervosa was recognised by doctors as an eating disorder in its own right. The term bulimia nervosa means literally 'the nervous hunger of an ox'. The hunger, however, is really an emotional need that cannot be satisfied by food alone. After binge-eating a large quantity of food to fill the emotional or hunger gap, there is an urge to immediately get rid of the food. Bulimia Nervosa is characterised by these episodes of binge eating (uncontrolled consumption of a large amount of food in a relatively short period of time) followed by an inappropriate "compensation" behaviour such as forced vomiting, laxative or diuretic abuse, a subsequent fast or period of food restriction, or excessive exercising.

Diagnostic criteria for Bulimia Nervosa also identify two sub-types of the disorder: purging and non-purging. Forced vomiting, or abuse of laxatives or diuretics, is considered "purging" whereas fasting or engaging in excessive exercise after a binge to compensate for the calories consumed is considered "non-purging". Sometimes the distinction between bulimia and the binge/purge type of anorexia is difficult to draw. However, if a patient meets all other criteria of anorexia nervosa, that is generally the diagnosis which is made.

Bulimia is more difficult for others to notice as the sufferer tends not to lose weight so dramatically, or their weight will fluctuate. People with bulimia may have demanding jobs that require them to be out-going and self-assured even when they feel inadequate inside. As with anorexia, people who develop bulimia become reliant on the control of food and eating as a way of coping with emotional difficulties in their life. During the binge episode, the individual experiences a loss of control. However, the sense of a loss of control is also followed by a short-lived calmness. The calmness is often followed by self-loathing. The cycle of overeating and purging usually becomes an obsession and is repeated often.

Eating Disorder Not Otherwise Specified (EDNOS)
Eating disorder not otherwise specified (EDNOS) is a diagnostic category of mental disorders that involve disordered eating patterns. It is described in the diagnostic manuals as a "category [of] disorders of eating that do not meet the criteria for any specific Eating Disorder". A diagnosis of EDNOS is frequently used for people who meet some, but not all, of the diagnostic criteria for anorexia nervosa or bulimia nervosa. For example, a person who shows almost all of the symptoms of anorexia nervosa, but who still has a normal menstrual cycle and/or body mass index, can be diagnosed with EDNOS. A sufferer may experience episodes of binging and purging, but may not do so frequently enough to warrant a diagnosis of bulimia nervosa. A person may also engage in binging episodes without the use of inappropriate compensatory behaviours; this is referred to as binge eating disorder. People diagnosed with EDNOS may frequently switch between different eating disorders, or may with time fit all diagnostic criteria for anorexia or bulimia.

EDNOS is a serious eating disorder, like anorexia and bulimia, with various subtypes (such as Binge Eating Disorder, Compulsive Overeating and Orthorexia Nervosa, as described below) and can have long-term consequences on the individual's physical health.

Binge Eating Disorder (BED)
Binge eating disorder is characterised by consuming large quantities of food in a very short period of time until the individual is uncomfortably full. It is similar to the eating disorder bulimia nervosa except the individuals do not use any form of purging following a binge. Additionally, people with bulimia are typically of normal weight or may be slightly overweight whereas people with binge eating disorder are typically overweight or obese. Individuals usually feel out of control during a binge episode, followed by feelings of guilt and shame. Many individuals who suffer with binge eating disorder use food as a way to cope with or block out feelings and emotions they do not want to feel. Individuals can also use food as a way to numb themselves, to cope with daily life stressors, to provide comfort to themselves or fill a void they feel within. Like all eating disorders, binge eating is a serious problem but can be overcome through proper treatment.

Binge eating disorder is similar to, but it is distinct from, compulsive eating. People with binge eating disorder do not have a compulsion to overeat and do not spend a great deal of time fantasising about food. On the contrary, some people with binge eating disorder have very negative feelings about food. As with other eating disorders, binge eating is an expressive disorder - that is, the disorder is an expression of a deeper, psychological problem.

Continual debate exists over whether binge eating disorder should have its own diagnosis. Some believe that it is a milder form, or subset of bulimia nervosa, but others argue that it is its own distinct disorder. Currently it is characterised under Eating Disorder Not Otherwise Specified (EDNOS), and the diagnostic manual simply states that ‘more research is needed’.

Compulsive Overeating
Compulsive overeating is characterised by an addiction to food. An individual suffering from compulsive overeating disorder engages in frequent episodes of uncontrolled eating, or binging, during which they may feel frenzied or out of control. They will eat much more quickly than is normal, and continue to eat even past the point of being uncomfortably full. Binging in this way is generally followed by a period of intense guilt feelings and depression. Unlike individuals with bulimia, compulsive overeaters do not attempt to compensate for their binging with purging behaviours such as fasting, laxative use or vomiting. Compulsive overeaters will typically eat when they are not hungry, spend excessive amounts of time and thought devoted to food, and secretly plan or fantasize about eating alone.