Eating disorders all have different symptoms, but basically, they each result from the fact that the individuals who suffer from them have difficulty separating their emotions from their eating habits. Indeed, they may even choose to use their eating habits to express their emotions and to 'communicate' with those around them. The way and the amount that they eat are seriously affected, and the long term effects can be devastating and sometimes fatal.

In the United States, the normal criteria for the diagnosis for eating disorders are contained in the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Association. In Europe, slightly different diagnostic criteria are uses.

DSM-IV recognises two distinct eating disorders - anorexia nervosa (anorexia), bulimia nervosa (bulimia). It has a further classification for "Eating Disorders Not Otherwise Specified" into which falls binge eating syndrome, a commonly diagnosed condition.

The diagnosis of Anorexia nervosa can be made if the patient fits the following criteria (Adapted from DSM-IV TR)):

• Refusal to keep body weight at or above that which is regarded as an acceptable minimum for age or height age and height:
• Weight loss causing body weight of <85% of that expected or failure to gain weight due to normal growth, resulting in body weight less than 85% of that expected.
• Anxiety about being perceived as fat, even though under weight.
• Distorted perceptions of body image, or denial of the existence of illness or the seriousness of current low body weight.
• Amenorrhea (for at least three menstrual cycles) in girls and women.

Anorexia nervosa has two sub-types, which can be present at different stages of the illness in the same person. Firstly, the "restricting" type, in which weight loss is achieved by severely restricting calorific intake without resort to laxative use or self-induced vomiting, and then the "Binge Eating-Purging" type, in which the sufferer may eat large amounts of food then attempts to eliminate the consequences by abusing laxatives.

Bulimia nervosa has the following diagnostic criteria (adapted from DSM-IVTR):

· Recurrent episodes of binge eating characterized by both:

1. Eating, within a given period of time), an amount of food that is significantly larger than most people would during a similar period
2. A feeling of inability over eating during the episode, identified by a belief that what is being eaten cannot be controlled.

· Frequent recurring inappropriate behaviour designed to prevent gaining weight

1. Self-induced vomiting
2. Abuse of enemas, laxatives or diuretics
3. Fasting
4. Excessive exercise
5. The binge eating and inappropriate behavior both occur, on average, at least twice a week for 3 months.
6. Self image and self esteem are dependent on perceptions of body shape and weight.

Bulimia, like anorexia falls into two sub types:

• Purging type: The person regularly self-induces and/or misuses of laxatives, enemas or diuretics.
• Nonpurging type: There is inappropriate compensatory behavior but no self-induced vomiting or medication misuse.

Binge Eating Disorder is best described as episodes of binge eating which are not characterised by the use of laxatives or self induced vomiting. Patients are often obese.

Night Eating Syndrome is disorder characterised by early morning lack of appetite, increased appetite in the evening and eating during the night. Strangely, patients often have total amnesia of their night eating episodes.

Other eating disorders commonly found before puberty include food avoidance, selective eating and pervasive food refusal syndrome. These childhood disorders are usually transient however.

Pica (the eating of faeces) and rumination (regurgitating and re-chewing of food) are not classified as eating disorders, although they are far from rare.

Eating disorders are much more common in women - ratios of 10:1 Female to Male have been suggested - and are also more prevalent in industrial societies where there is an over-abundance of food. The commonly accepted idea that a woman has to be slim to be attractive is also a factor in the prevalence of eating disorder, particularly in Europe and the US.

Eating disorders often co-exist with other psychological disturbances. 50% to 70% of sufferers will typically also suffer from depression, 25% -to 50% may have been (or are being) sexually abused, and up to 25% will suffer from Obsessive compulsive disorder. Substance abuse is also common.

Typically, eating disorder behaviour is highly secretive, and accompanied by sever guilt feelings. Obsessive thinking about food, hoarding food and even collecting recipes are frequently observed behaviors.

Treatment for eating disorders is complex, as any co-existing factors have to be taken into account. Cognitive Behavioural Therapy (a fairly brief and highly interactive therapy has proved useful, as has medication in the case of bulimia nervosa. Anorexia nervosa has so far proved difficult to treat with medication.

Family support is essential, and online self help or support groups have a large part to play in successful treatment.

Long term outcomes are variable, with about 0ne third of sufferers making a total recovery, one third retaining a low degree of eating disorder, and the final one third maintaining chronic eating disorder problems.