What is an eating disorder?

What are the main types of eating disorders?

Page last updated: May 2007

The two most serious eating disorders are anorexia nervosa (anorexia) and bulimia nervosa (bulimia).


Anorexia is characterised by an intense fear of being obese and a relentless pursuit of thinness. Its symptoms include:
  • A loss of at least 15 percent of body weight resulting from refusal to eat enough food, despite extreme hunger.
  • An intense fear of becoming 'fat' and of losing control.
  • A disturbance of perception of body image in that people may regard themselves as fat, over estimating body size the thinner they become.
  • A tendency to exercise obsessively.
  • A preoccupation with determining 'good' and 'bad' foods, and with the preparation of food.
  • Absence of menstrual periods.
Often, anorexia begins with a weight loss, resulting from either dieting or physical illness. Positive comments about the weight loss seem to encourage the person to believe that if thin is good, thinner is better.

Starvation and erratic eating patterns can then become anorexia.

A significant proportion of people with anorexia will also develop bulimia.


Bulimia is characterised by bingeing and purging. Its symptoms include:
  • Eating binges that involve consumption of large amounts of calorie-rich foods, during which the person feels a loss of personal control and self-disgust.
  • Purging attempts to compensate for binges and to avoid weight gain by self induced vomiting, and/or misuse of laxatives and fluid tablets.
  • A combination of restricted eating and compulsive exercise so that control of weight dominates the person’s life.
A person with bulimia is usually close to their normal body weight, so is less recognisable than a person with anorexia.

Bulimia often starts with rigid weight reduction dieting in the pursuit of thinness. Inadequate nutrition causes tiredness and powerful urges to binge eat.

Vomiting after a binge seems to bring a sense of relief, but this is temporary and soon turns to depression and guilt.

Some people use laxatives, apparently unaware that laxatives do not reduce kilojoules/fat content, and only serve to eliminate vital trace elements and dehydrate the body.

People with bulimia may experience chemical imbalances in their body that bring about lethargy, depression and clouded thinking.

The person can make strong efforts to break the pattern, but the vicious binge/purge/exercise cycle and the feelings associated with it, become compulsive and uncontrollable.

Binge eating disorder

This eating disorder has only recently been recognised. People with binge eating disorder have episodes of binge eating in which they consume extreme quantities of food within short periods of time, and feel out of control while they are bingeing.

However, they do not make attempts to purge their food after bingeing. The binge eating can lead to serious health consequences such as obesity, diabetes, hypertension and cardiovascular disease.

Co-occurring mental health problems

Eating disorders often co-occur with anxiety disorders such as panic disorder and obsessive compulsive disorder, as well as with harmful substance use. For more information on anxiety, read the brochure What is an anxiety disorder?

Physical effects of anorexia and bulimia

The physical effects of anorexia and bulimia can be very serious, but are generally reversible if the illness is treated early. If left untreated, severe anorexia and bulimia can be life-threatening.

Both illnesses, when severe, can cause:
  • Harm to the kidneys.
  • Urinary tract infections and damage to the colon.
  • Dehydration, constipation and diarrhoea.
  • Seizures, muscle spasms or cramps.
  • Chronic indigestion.
  • Loss of menstruation or irregular periods.
  • Strain on most body organs.
Many of the effects of anorexia are related to malnutrition, including:
  • Absence of menstrual periods.
  • Severe sensitivity to the cold.
  • Growth of down-like hair all over the body.
  • Inability to concentrate and think rationally.
Severe bulimia is likely to cause:
  • Erosion of dental enamel from vomiting.
  • Swollen salivary glands.
  • Chronic sore throat and gullet.
  • Intestinal and stomach problems.
Emotional and psychological effects include:
  • Difficulty with activities that involve food and deceptive behaviours related to food.
  • Loneliness, due to self-imposed isolation and a reluctance to develop personal relationships.
  • Fear of the disapproval of others if the illness becomes known.
  • Mood swings, changes in personality,emotional outbursts and depression.
Responding to early warning signs and obtaining early treatment for anorexia and bulimia is, therefore, essential.