What is Anorexia Nervosa?

Written by Emily Green

Potentially the most well known type of eating disorder, anorexia nervosa (AN) is a serious and incredibly isolating mental illness with a high mortality rate. Contrary to this however, AN actually only accounts for approximately 10% of eating disorder diagnoses (1). AN is a restrictive eating condition characterised by avoidance of eating, lower than optimal body weight and severe anxiety around food and weight gain.

How is Anorexia Nervosa Diagnosed?

AN is defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) (2) according to diagnostic criteria, subtype and severity. Typically AN is diagnosed when the following criteria are met:

A. Restriction of energy intake relative to requirements, leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health. Significantly low weight is defined as a weight that is less than minimally normal or, for children and adolescents, less than minimally expected.

B. Intense fear of gaining weight or of becoming fat, or persistent behaviour that interferes with weight gain, even though at a significantly low weight.

C. Disturbance in body weight or shape perception, undue influence of body weight or shape on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight.

Diagnoses are further specified depending on subtype. This considers the following symptoms and behaviours in the preceding 3 month period:

Restricting subtype

The individual has not engaged in recurrent episodes of binge eating or purging behaviour (i.e. self-induced vomiting, or the misuse of laxatives, diuretics, or enemas). This subtype describes presentations in which weight loss is accomplished primarily through dieting, fasting and/or excessive exercise.

Binge-eating/purging subtype

The individual has engaged in recurrent episodes of binge eating or purging behaviour (i.e. self-induced vomiting, or the misuse of laxatives, diuretics, or enemas).


The severity of AN is defined in the DSM-V using the following BMI categories:

Mild: BMI >17

Moderate: BMI 16-16.99

Severe: BMI 15-15.99

Extreme: BMI <15

It is important to note that although this criteria is included in the DSM-V, at TCN we understand that BMI doesn't necessarily reflect the severity of an eating disorder like anorexia nervosa. BMI can potentially be used to guide clinical assessment and recommendations, however we believe that everyone deserves accesses to treatment regardless of body shape, size or weight.

Who Does Anorexia Nervosa Affect?

Eating disorders do not discriminate, they can affect all genders, races and ages.

It's tricky to pinpoint an exact prevalence of AN but it is estimated that it affects around 0.3% of females (29,267) and 0.1% of males (10,504) aged 11-34yrs in the UK (3), with the common age of onset at 16-17yrs (1).

Males account for approximately 25% of all AN cases but are at increased risk of poor outcomes due to a typically later diagnosis (4), where early interventions have been shown to improve outcomes in symptoms and recovery.

Contrary to popular depictions, AN can affect individuals at any weight and those with the condition may not always appear underweight or unwell. There can be increased risks related to anorexia for people in larger bodies due to practitioner’s implicit or explicit weight bias and prejudice. This can delay timely diagnosis or prevent proper care and treatment from being provided.

What are the warning signs?

Although the signs of eating disorders are not always obvious, there are some common red flags which may indicate a person is struggling. These can show up in eating behaviours, thoughts and perceptions, physical wellbeing or emotional changes:

●Ritualistic behaviours around food

●High levels of perfectionism

●Rigid black and white thinking exhibited as strict food rules

●Regular weighing where the number on the scale impacts mood for the whole day

●Avoiding eating with others or avoiding social events

●Social withdrawal and isolation

●Excessive or compulsive exercise for the purpose of weight loss not enjoyment

●Body checking, skin pinching, looking in mirrors obsessively

●Intense anxiety around food and eating

●Absence of menstruation - a lost menstrual cycle or delayed onset of the first period

How Does Anorexia Nervosa Develop?

There is no single root cause of AN, but often a mixture of historical factors which put someone at increased risk and a distressing trigger such as trauma, bereavement or stressful life changes. Research in this area generally accepts that eating disorders have many interconnected risk factors which fall under psychological, environmental (i.e. socio-cultural) and biological (includes genetics).

Research into a potential genetic link is still ongoing and includes twin studies and genome-wide association studies to identify if any specific genes are related to AN (5).

Family history of eating disorders and mental illness can also be a risk factor. Several studies have linked the presence of AN to obsessive compulsive disorder (OCD) and mood disorders (e.g. depression, bipolar disorder) within families (6, 7). This suggests that eating disorders and mood disorders may have common causal factors.

Similarly, the home environment plays a key role; maternal eating disorders have been shown to predict body dissatisfaction in daughters and dieting in sons (8). And a difficult relationship between parent and child can exacerbate body and weight issues, increasing the risk of eating disorders (9). However this is more likely to be related to the environment in which a child grows up and behaviours or attitudes they adopt from parents, rather than a causative genetic-basis.

The important thing to remember about risk factors and genetics is that it is not black and white. Being at an increased risk of developing an eating disorder does not necessarily mean a person will develop an eating disorder.

What to Expect in Treatment for Anorexia Nervosa?

Eating disorders are complex, multi-faceted conditions, so treatment should involve a multi-disciplinary team. Typically, the first point of contact is a GP and they will refer you onto a specialist team including a psychological professional and registered dietitian.

Treatment is a long-term process and aims to restore the physical health of the individual through supervised weight restoration and address the factors maintaining the eating disorder. These maintaining factors can be categorised as clinical perfectionism, core low self esteem, mood intolerance and interpersonal difficulties (10).

Typical treatment programs include:

Maudsley Anorexia Nervosa Treatment for Adults (MANTRA)

Family Therapy for under 18s

CBT-E (Cognitive Behavioural Therapy for eating disorders)


Guided self help


Specialist supportive clinical management (SSCM)

Treatment can be successful in an outpatient setting, but some cases require inpatient care if there are concerns about continued weight loss, risk to life or the patient is under 18 without sufficient support at home (11).

Working With a Dietitian in Recovery

Recovery is possible for everyone! A dietitian is a key part of the multi-disciplinary eating disorder recovery team. They will work alongside medical and psychological professionals to help a person achieve full recovery.

At the TC Nutrition Clinic, our dietitians support and guide people with:

●Weight restoration

●Establishing regular eating patterns

●Helping normalise relationship with food

●Overcoming food rules and fears

●Improving body image

●Improving gastrointestinal symptoms (bloating, constipation, discomfort)

●Normalising food choices in a social context

●Replacing unhealthy compensatory behaviours (laxative abuse, purging) with healthy behaviours

If you recognise any of these red flags in your own thoughts and behaviours, or know you struggle with anorexia nervosa, please reach out to us for support at info@taliacecchele.com and book a free discovery call with us.

Emily Green