Age-specific changes in BMI and BMI distribution among Australian adults using cross-sectional surveys from 1980 to 2008.

BACKGROUND: Research efforts have focused mainly on trends in obesity among populations, or changes in mean body mass index (BMI), without consideration of changes in BMI across the BMI spectrum. Examination of age-specific changes in BMI distribution may reveal patterns that are relevant to targeting of interventions. METHODS: Using a synthetic cohort approach (which matches members of cross-sectional surveys by birth year) we estimated population representative annual BMI change across two time periods (1980 to 1989 and 1995 to 2008) by age, sex, socioeconomic position and quantiles of BMI. Our study population was a total of 27349 participants from four nationally representative Australian health surveys; Risk Factor Prevalence Study surveys (1980 and 1989), the 1995 National Nutrition Survey and the 2007/8 National Health Survey. RESULTS: We found greater mean BMI increases in younger people, in those already overweight and in those with lower education. For men, age-specific mean annual BMI change was very similar in the 1980s and the early 2000s (P=0.39), but there was a recent slowing down of annual BMI gain for older women in the 2000s compared with their same-age counterparts in the 1980s (P<0.05). BMI change was not uniform across the BMI distribution, with different patterns by age and sex in different periods. Young adults had much greater BMI gain at higher BMI quantiles, thus adding to the increased right skew in BMI, whereas BMI gain for older populations was more even across the BMI distribution. CONCLUSIONS: The synthetic cohort technique provided useful information from serial cross-sectional survey data. The quantification of annual BMI change has contributed to an understanding of the epidemiology of obesity progression and identified key target groups for policy attention-young adults, those who are already overweight and those of lower socioeconomic status.

Trends in body mass index according to educational attainment for urban Australian adults between 1980 and 2007.

BACKGROUND: We have previously demonstrated that between the years 1980 and 2000, the mean body mass index (BMI) of the urban Australian population increased, with greater increases observed with increasing BMI. The current study aimed to quantify trends over time in BMI according to level of education between 1980 and 2007. METHODS: We compared data from the 1980, 1983 and 1989 National Heart Foundation Risk Factor Prevalence Studies, 1995 National Nutrition Survey, 2000 Australian Diabetes, Obesity and Lifestyle Study and the 2007 National Health Survey. For survey comparability, analyses were restricted to urban Australian residents aged 25-64 years. BMI was calculated from measured height and weight. The education variable was dichotomised at completion of secondary school. Four age-standardised BMI indicators were compared over time by sex and education: mean BMI, mean BMI of the top 5% of the BMI distribution, prevalence of obesity (BMI⩾30 kg m(-)(2)), prevalence of class II(+) obesity (BMI⩾35 kg m(-)(2)). RESULTS: Between 1980 and 2007, the mean BMI among men increased by 2.5 and 1.7 kg m(-)(2) for those with low and high education levels, respectively, corresponding to increases in obesity prevalence of 20 (from 12-32%) and 11 (10-21%) %-points. Among women, mean BMI increased by 2.9 and 2.4 kg m(-)(2) for those with low and high education levels, respectively, corresponding to increases in obesity prevalence of 16 (12-28%) and 12 (7-19%) %-points. The prevalence of class II(+) obesity among men increased by 9 (1-10%) and 4 (1-5%) %-points for those with low and high education levels, and among women increased by 8 (4-12%) and 4 (2-6%) %-points. Absolute and relative differences between education groups generally increased over time. CONCLUSIONS: Educational differences in BMI have persisted among urban Australian adults since 1980 without improvement. Obesity prevention policies will need to be effective in those with greatest socio-economic disadvantage if we are to equitably and effectively address the population burden of obesity and its corollaries.

A systematic review of the effectiveness of whole-of-community interventions by socioeconomic position.

Whole-of-community (WOC) interventions have led to modest reductions in population weight gain. Whether they exhibit differential effectiveness by socioeconomic position (SEP) remains unknown. We aimed to summarize evidence of differential effectiveness of WOC interventions by SEP. Electronic databases and grey literature were searched to identify studies that evaluated the effectiveness of a WOC intervention on behavioural change measures, energy balance behaviours and/or anthropometric outcomes according to any measure of SEP. Interventions were assessed for the following characteristics: structural changes to the environment, number of settings the intervention acted in, presence of community engagement and whether equity was considered in its design. Ten studies were included. Nine reported a greater or equal effect among low SEP groups compared with high SEP groups. These studies commonly featured interventions that incorporated structural changes to the environment, acted across more than three settings and/or employed community engagement. Conclusions did not change when excluding low-quality studies (n = 4). WOC interventions represent an effective and equitable approach for the reduction of population weight. Structural components, a larger number of settings and community engagement were common in equitable WOC interventions and should be considered in the design of future WOC interventions.