EATING DISORDER - ANOREXIA IN TEENS

Eating disorders are fairly common, fortunately the severe variety such as anorexia is least common. This article focuses anorexia in teenage girls, you may download a more detailed power point version of this article.

Normal physiology in teenage girls (anorexia disrupts this significantly)

  • Puberty – occurs over a range of 4-5 years
  • Peak height velocity for girls is at 11.5 on average (growing on average 9 cm per year).
  • Menarche is one of the last events of puberty.
  • Puberty / Growth Spurts - Growth is especially rapid during puberty, with girls’ mean weight increasing from 34 kg at age 11 years to 48 kg at age 13 years; this represents a 41% increase in 2 years.
  • The estimated average energy requirement in the UK for healthy girls aged 11–18 years ranges from 1845 kcal to 2110 kcal

Clinical features and physiological features of anorexia:

  • Starts as adolescent preoccupation with diet / weight
  • Weighing several times a day
  • Downward setting of weight goals
  • Growing list of forbidden food
  • Egosyntonic thinking (person does not think there is a problem)
  • Self-induced weight loss by - Skipping meals, avoidance of "fattening foods", self-induced vomiting / purging, excessive exercise, use of appetite suppressants, diuretics and Laxatives.
  • There is body-image distortion with an intrusive dread of fatness - the patient imposes a low weight threshold on himself or herself.
  • Presence or absence of binges
  • Co-morbid emotional disorders
  • Body weight 15% below that expected weight for height
  • Pre-pubertal patients fail to make the expected weight gain, delayed or arrested puberty.
  • A widespread endocrine disorder manifest as amenorrhoea

For details on adverse effects of different body parts go to the presentation

BMI is not helpful in Children and Adolescents: The average BMI in childhood changes substantially with age. At birth = 13 kg/m2, increases to 17 at age 1, decreases to 15.5 at age 6, then increases to 21 at age 20. It hence unreliable as a sole clinical marker in young people. Other factors also make it unreliable, these are detailed on the slide presentation.

Treatment

  • Motivational interviewing / Education
  • Re-feeding syndrome – oedema (usually normal), cardiac and respiratory failure, delirium & fits.
  • Nutritional supplements & monitoring of bloods
  • Dietetics - Daily intake initially may be ~ 800 (start low in cases with high risk of re-feeding syndrome) to 1800 cal but would have to go up to 3000 cal / day - depends also on level of physical activity, to account for expected growth, a positive energy balance is needed. A weekly weight gain of 0.5 to 1 kg in inpatient settings and 0.5 kg in outpatient settings should be an aim of treatment.
  • Target weights need changes if growth spurt happens during re-feeding.
  • Family Therapy - mobilise family resources to improve intake first before treating family dysfunction.
  • Cognitive Analytical Therapy / Interpersonal Therapy / CBT (more robust evidence for BN)
  • Medication – symptomatic (medical) and for psychiatric co-morbidity only (anecdotal use of Olanzapine may help with cognitive rigidity; anti-depressants for severe anxiety or mood problems).

Dr A Joglekar