Differences between birth cohorts

This section compares estimates of the prevalence of overweight and obesity combined, obesity alone, severe obesity and abdominal obesity, and median BMI between different birth cohorts when they are at the same age. The interactive graph below allows you to explore these different measures of overweight and obesity across the birth cohorts.

For each age group, the birth cohort born most recently (measured in 2017–18) is compared with the birth cohort born 10 years earlier at the same age (measured in 2007–08).

Figure 1: Prevalence of overweight and obesity, and median BMI, by age group; 2007–08 and 2017–18

These bar charts show the prevalence of 4 measures of overweight and obesity: overweight and obesity combined, obesity alone, severe obesity and abdominal obesity, as well as the median BMI. The measures are shown for 8 age groups, at 2 time points for each group (2007–08 and 2017–18). For most age groups, the prevalence of all measures of overweight and obesity was generally higher for the birth cohort born most recently (measured in 2017–18), compared with the cohort born 10 years earlier at the same age (measured in 2007–08). Median BMI of those born most recently was higher than that of those born 10 years earlier for all adult age groups included.

Visualisation not available for printing

Overweight and obesity

For all age groups except 5–14, 55–64 and 65–74, those born most recently were significantly more likely to be overweight or obese than those born 10 years earlier. The largest absolute difference was at age 75–84, where an additional 7 in every 100 adults were overweight or obese at age 75–84 in 2017–18 compared with 2007–08.

The 5–14, 55–64 and 65–74 age groups followed a similar pattern, however the difference in the prevalence of overweight and obesity between the birth cohorts was not statistically significant (Figure 1, tables S2 and S3).

Obesity

For all age groups except 5–14 and 15–24, those born most recently were significantly more likely to be obese than those born 10 years earlier. The largest absolute difference was at age 75–84, where an additional 11 in every 100 adults were obese at age 75–84 in 2017–18 compared with 2007–08.

The 5–14 and 15–24 age groups followed a similar pattern, however the difference in the prevalence of obesity between the birth cohorts was not statistically significant (Figure 1, tables S2 and S3).

Severe obesity

In this report, severe obesity is defined as a BMI of 35 kg/m2 or more in adults. The analysis of severe obesity is limited to adults due to a lack of consensus on the definition for children and adolescents.

For all adult age groups except 35–44, those born most recently were significantly more likely to be severely obese than those born 10 years earlier. The largest absolute difference was at age 65–74, where an additional 7 in every 100 adults were severely obese at age 65–74 in 2017–18 compared with 2007–08.

The 35–44 age group followed a similar pattern, however the difference in the prevalence of severe obesity between the birth cohorts was not statistically significant (Figure 1, tables S2 and S3).

Abdominal obesity

In this report, abdominal obesity is defined as a waist circumference of 102 cm or more in men and 88 cm or more in women (WHO 2000). The analysis of abdominal obesity is limited to adults due to a lack of consensus on the definition for children and adolescents.

For the 45–54, 65–74 and 75–84 age groups, those born most recently were significantly more likely to be abdominally obese than those born 10 years earlier. The largest absolute difference was at age 45–54, where an additional 9 in every 100 adults were abdominally obese at age 45–54 in 2017–18 compared with 2007–08.

The 25–34 and 35–44 age groups followed a similar pattern, however the difference in the prevalence of abdominal obesity between the birth cohorts was not statistically significant, and the 55–64 age group showed little difference between the birth cohorts (Figure 1, tables S2 and S3).

Median BMI

Analysis of the median BMI (or 50th percentile) shows the differences between cohorts in what is considered a typical BMI. This analysis is limited to adults due to the age- and sex-specific BMI cut-offs for measuring overweight and obesity in children and adolescents.

For all adult age groups, the median BMI of those born most recently was significantly higher than that of those born 10 years earlier (Figure 1, Table S4). The largest absolute difference was at age 75–84, where the median BMI was 1.4 kg/m2 higher at age 75–84 in 2017–18 compared with 2007–08.

References

ABS (Australian Bureau of Statistics) 2009. Microdata: National Health Survey, Basic and Expanded CURF, 2007–08. ABS cat. no. 4324.0.55.001. Findings based on Expanded Confidentialised Unit Record File analysis. Canberra: ABS.

ABS 2019. Microdata: National Health Survey, 2017–18. ABS cat. no. 4324.0.55.001. Findings based on Detailed Microdata analysis. Canberra: ABS.

WHO (World Health Organization) 2000. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. WHO Technical Report Series 894:i–xii, 1–253.