Summary

Overweight and obesity is a major public health issue, second only to tobacco smoking as a risk factor contributing to the burden of disease in Australia. This report looks at the prevalence of overweight and obesity by birth cohort to examine potential differences at a given age between people born most recently and those born 4, 8, and 20 years earlier.

Adults in 2014–15 were more likely to be obese than adults of the same age 20 years earlier

Based on body mass index (BMI), adults in 2014–15 were significantly more likely to be obese than those 20 years earlier in all but 1 of the age groups assessed. The largest relative difference across cohorts was at age 18–21—15.2% of those born in 1994–1997 were obese at that age, almost double the proportion of those born in 1974–1977 (8.0%). When broken down by sex, men and women were significantly more likely to be obese at most ages than their counterparts 20 years earlier.

Adults in 2014–15 were more likely to be abdominally obese than adults of the same age 20 years earlier

Based on waist circumference, adults at every age in 2014–15 were significantly more likely to be abdominally obese than those 20 years earlier. The largest relative difference was among adults aged 18–21—16.5% of those born in 1994–1997 were abdominally obese at that age, more than double the proportion of those born in 1974–1977 (7.2%).

Children and adolescents aged 10–17 in 2014–15 were more likely to be overweight or obese than those 20 years earlier

Based on BMI, children and adolescents in 2014–15 were significantly more likely to be overweight or obese at ages 10–13 and 14–17 than those 20 years earlier. At age 10–13, 30.8% of children and adolescents born in 2002–2005 were overweight or obese, compared with 23.9% of those born in 1982–1985. At age 14–17, 29.8% of adolescents born in 1998–2001 were overweight or obese, compared with 18.7% of those born in 1978–1981. There were no statistically significant differences for overweight and obesity at ages 2–5 and 6–9.

Children aged 2–5 in 2014–15 were twice as likely to be obese than those 20 years earlier

For obesity alone, children at age 2–5 in 2014–15 were significantly more likely to be obese than those 20 years earlier (8.8% compared with 4.2%). There were no statistically significant differences for obesity alone at ages 6–9, 10–13, and 14–17. When broken down by sex, boys in 2014–15 were significantly more likely to be obese at ages 2–5 and 10–13, compared with those born 20 years earlier. Girls in 2014–15 were significantly more likely to be obese at age 2–5 and 14–17, compared with those born 20 years earlier.

What are the implications?

Given obesity is a risk factor for several chronic conditions, the increased prevalence of obesity at younger ages among those born more recently is likely to be followed by a higher prevalence of obesity-related chronic conditions at younger ages. This will in turn lead to higher health care costs.