What is anorexia nervosa?

Anorexia nervosa is a serious eating disorder where individuals become intensely focused on their weight, body shape, and food consumption, leading them to severely restrict their eating to the point of self-starvation. This condition often develops gradually over several years, particularly in people with certain genetic factors, emotional vulnerabilities, or challenging life experiences. The term 'anorexia' is often used interchangeably with anorexia nervosa, specifically referring to the behaviour of self-starvation.

This disorder revolves around an overwhelming preoccupation with body weight, which might manifest as an intense fear of gaining weight or an unrelenting drive to become thinner. As a result, individuals maintain a body weight that is much lower than what is healthy for their age, height, and build.

Symptoms and diagnostic criteria

The symptoms of anorexia nervosa typically build up over time and centre on distorted perceptions of body image and extreme measures to control weight. These symptoms not only affect eating habits but also influence daily life, emotions, and physical health.

Key symptoms of anorexia nervosa

• Severe restriction of food intake - Individuals deliberately limit what they eat, often avoiding entire food groups or consuming very small portions, leading to significant weight loss.
• Intense fear of weight gain - Even when underweight, there is a persistent dread of becoming fat, which drives ongoing efforts to lose more weight.
• Distorted body image - People with anorexia often see themselves as overweight despite being thin, and they may engage in behaviours like frequent weighing or mirror checking.
• Denial of the seriousness of low weight - There is often a refusal to acknowledge the health risks associated with their low body weight.

Diagnostic criteria based on weight

Diagnosis involves assessing whether body weight falls below healthy levels. Body mass index (BMI) is a key measure here, calculated as a person's weight in kilograms divided by the square of their height in metres (kg/m²).

Formula for BMI:

$\text{BMI}=\frac{\text{weight (kg)}}{{\text{height (m)}}^2}$

Key weight-related criteria:

• Adults - Weight is at least 15% below what is expected for their height and age, or BMI is below 17.5 kg/m².
• Younger individuals - During puberty, diagnosis may apply if expected weight gain during a growth spurt does not occur, resulting in becoming underweight without actual weight loss.

These criteria help distinguish anorexia from other conditions, ensuring that the focus is on the combination of low weight and psychological factors.

Physical effects on the body

The self-starvation and related behaviours in anorexia nervosa have widespread impacts on the body, as every system is affected by starvation. Additionally, some individuals engage in purging behaviours, which add further complications.

Effects on major body systems

• Muscular system - Leads to weakness and loss of muscle strength, including weakening of the heart muscle.
• Skeletal system - Causes loss of bone density and can impair linear growth.
• Endocrine system - Results in infertility and reduced mineral content in bones.
• Dental and oral health - Purging behaviours erode tooth enamel, leading to worn, painful teeth that affect comfort, appearance, and self-esteem.

Prevalence and demographic patterns

This disorder is more common in certain groups, though it can affect anyone regardless of background.

Key statistics on prevalence

• Overall occurrence - Approximately 10% of all eating disorder cases are anorexia nervosa.
• Lifetime risk for women - Between 1 and 4.2% of women experience anorexia at some point in their lives.
• Age of onset - The condition typically first appears around mid to late adolescence.

Demographic patterns

• Gender distribution - It affects about 1% of women aged between 15 and 30.
• Development over time - Symptoms often emerge gradually, influenced by genetic predispositions, emotional factors, or life experiences, rather than appearing suddenly.