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Morbid Obesity C031

Last amended 
4 July 2019

In this section

Current RMA Instruments
Reasonable Hypothesis
5 of 2014 as amended by 75 of 2019
Balance of Probabilities

6 of 2014 as amended by 76 of 2019

Changes from previous Instruments

SOP Bulletin 209

ICD Coding
  • ICD-9-CM Codes: 278.0
  • ICD-10-AM Codes: E66.8
Brief description

This is a condition where excessive accumulation of fat in the body results in a body mass index (BMI) of 40 kg/m2 or higher, in adults.  Note that there is a different criterion for persons aged 18 years or younger (see SOP definition).

Confirming the diagnosis

The diagnosis is made by calculating the person's BMI from their height and weight.  Note that the SOP definition previously specified a current BMI, but that requirement has been removed.  If a person's BMI has been at or over the threshold in the past, but the current BMI is below the threshold, then the SOP may still be applicable.  Examples may include: where a person has undergone bariatric surgery for morbid obesity; and, where a person's BMI has fluctuated above and below the threshold and is currently slightly below.  In cases where the BMI is not currently at or above the threshold at the time a cliam is made the individual circumstances should be considered and medical advice sought as to whether a morbid obesity diagnosis is warranted.

Body mass index = [Mass in kg] divided by [height in metres, squared]  =  (kg/m2).

The  World Health Organisation Body Mass Index charts referred to in the SOP definition, for persons aged 18 years or younger, are linked below.

WHO BMI girls

WHO BMI boys

Additional diagnoses covered by SOP
  • Nil
Conditions excluded from SOP
  • Obesity – not a disease or injury - see the RMA declaration
  • Overweight – not a disease or injury.
Clinical onset

Clinical onset of morbid obesity is when the person first reached the BMI threshold.  If a person's weight subsequently fluctuated below and then back above the threshold, that will not represent a new clinical onset in most circumstances (unless there has been a substantial decrease in BMI and that decrease was maintained for a significant period of time).

Clinical worsening

The only SOP worsening factor is for inability to obtain appropriate clinical management. Clinical worsening may be evidenced by a significant increase in weight, beyond the normal weight trajectory or pattern for that person.