• Summary
• Downloads
• Explanatory Notes
• Related Information
• Past Releases

BODY MASS AND PHYSICAL MEASUREMENTS

Definition

This topic refers to respondents' physical measurements and other self-perception questions including:

• The height (cm), weight (kg) and waist circumference (cm) of respondents as measured during the interview
• Body mass index (BMI) derived from the height and weight physical measurements
• Self-perceived body mass.

Physical Measurements

Physical measurements were taken towards the end of the survey. All physical measurements were voluntary, and women who volunteered at this point in the interview that they were pregnant were not measured. Interviewers used digital scales to measure weight (maximum 150kg), a stadiometer to measure height (maximum 210cm), and a metal tape measure (which avoided the risk of the tape stretching) to measure waist circumference (maximum 200cm). Thorough interviewer training identified the points at which waists were to be measured as recommended by a World Health Organisation report as well as how to take the measurements with the least amount of respondent discomfort. For waist measurements, interviewers held the end of the tape at the appropriate point and asked the respondent to turn around until the tape met, or asked the respondent to hold the end of the tape and walked around them until the tape met.

Interviewers encouraged respondents to remove their shoes and any heavy clothing, e.g. jumpers, before they took measurements, however, this was voluntary, and may not have occurred in some cases. Interviewers were not required to record if they thought clothing may have impacted significantly on measurements. Weight was recorded in kilos to one decimal point, and height and waist measurements were recorded in centimetres to one decimal point. Waist measurements were taken by placing the tape measure across the top of the belly button. If a respondent's waist measurement was more than two meters (the maximum measurement of the tape measure), interviewers were instructed to record this as 200.0cm. If a respondent's weight was self-reported to be more than 150 kilograms (the maximum measurement of the scales used) the interviewer was instructed to record 999.9 kg and include a comment in the instrument, however some interviewers recorded weights above 150kg and these records were included in output.

In order to validate the height and waist measurements, a random 10% of respondents were selected to be measured an additional time. If this second measurement of height or waist varied by more than one centimetre then a third reading was taken. Weight measurements were only taken once. For output purposes only the first measurement is used.

Body Mass Index

Body mass index (BMI) scores were derived using Quetelet's metric body mass index which is calculated as weight (kg) divided by height (m)². BMI scores are commonly grouped for output. Whist the cut off points for different ethnic groups can vary, the World Health Organisation recommends that the same cut off points be used for international classification. The detailed output classifications available are shown in the table below. 2014-15 NHS publications use aggregated categories for estimates in published tables.

Category		BMI score
Underweight
	Class 3	Less than 16
	Class 2	16.0 to less than 17.0
	Class 1	17.0 to less than 18.5
Normal range
	Normal	Adult: 18.5 to less than 20.0; Child: 18.5 to less than 25.0(a)
	Normal (Adult only)	20.0 to less than 25.0
Overweight
		25.0 to less than 30.0
Obese
	Class 1	Adult: 30.0 to less than 35.0; Child: 30.0 or more (a)
	Class 2 (Adult only)	35.0 to less than 40.0
	Class 3 (Adult only)	40 or more

	Not at risk	Increased risk	Substantially increased risk
Males	Less than 94 cm	94 cm or more	102 cm or more
Females	Less than 80 cm	80 cm or more	88 cm or more

• Acceptable weight
• Underweight
• Overweight.

• A female had previously identified themselves as currently pregnant (or raised it at this point).
• A proxy was being used for a respondent aged 15-17 years
• A proxy was being used for an adult interview and the respondent was not present.

• BMI was calculated for persons for whom height and weight were measured or imputed (for further information see Imputation). For 2014-15, 71.8% of respondents aged 2 years and over had their height and weight measured (i.e. This comprises 61.3% of children aged 2-17 who had their height and weight measured, and 74.5% of respondents 18 years and over who had their height and weight measured. However, to allow for the calculation of BMI for all fully responding persons, imputation was used to obtain values for respondents for whom physical measurements were not taken. The results presented as part of the 2014-15 NHS include both measured and imputed data. An investigation was undertaken to determine whether the characteristics of the people who were measured differed from those who were not measured. This investigation looked at variables such as smoking status, self-assessed health, employment status, marital status, country of birth, self perceived body mass, level of exercise and whether or not has high cholesterol (as a long-term health condition) and found no differences. While there were some differences in age, sex and part of state, these were taken account of in the weighting process. For more detail on response rates see Response rates.
• Non-response rates for physical measurements were higher in 2014-15 than in 2011-12; for example, the non-response for BMI for adults in 2014-15 was 26.8% compared with 16.5% in 2011-12.
• While BMI is a useful tool to assess and monitor changes in body mass at the population level, it may be an inappropriate measure of the body fatness of certain populations and certain individuals; for example, those whose high body mass is due to muscle rather than fat, those with osteoporosis who have lower than usual BMI, or those of non-European background, whose risk levels are not accurately reflected in the BMI cut-off points used. BMI can, however, be used in conjunction with waist circumference which provides a second indicator for people at risk.
• Respondents were not specifically asked whether they were pregnant, however they were able to volunteer this during the interview. If the respondent volunteered that they were currently pregnant, the interviewer was instructed not to take their measurements and to explain to the respondent that the measurements during the course of a pregnancy will not accurately reflect their general (i.e. non-pregnant) measures.
• If physical measurements were taken prior to being informed that the respondent was pregnant, interviewers were instructed to include a comment in the instrument confirming that the measurements taken were of a pregnant respondent, their results were excluded.

• Where possible, comparisons are made using the Australian Health Survey: Updated Results, 2011-12 (cat. no. 4364.0.55.003) and Microdata: Australian Health Survey, Core Content - Risk Factors and Selected Health Conditions, 2011-12 (cat. no. 4324.0.55.003) for the most accurate information.
• For comparison of 2014-15 data with items which were only collected in the 2011-12 NHS, the Australian Health Survey: First Results, 2011-12 (cat. no. 4364.0.55.001) and Microdata: Australian Health Survey, National Health Survey, 2011-12 (cat. no. 4324.0.55.001) are used.
• When comparing individuals physical measured weight in kilograms or items derived from this, for example BMI, it should be noted that some physical weights above 150 kg have been recorded in 2014-15 NHS. In 2011-13 AHS no physical weights were recorded above the scale measure of 150 kg.

• 'Self-assessed body mass compared to 12 months ago' was not collected in the 2014-15 NHS, but was in the 2011-12 NHS.
• In the 2014-15 NHS, where provided, self reported data for height, weight or waist measurements has been included on the output file, along with self report flags to identify this data.