OBESE NATION: It’s time to admit it – Australia is becoming an obese nation. This series looks at how this has happened and, more importantly, what we can do to stop the obesity epidemic.

Here, Kathryn Backholer and Anna Peeters look at the relationship between socioeconomic status and weight, while Suzie Ferrie explains why a fat tax won’t be enough to curb the problem.

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We’ve long known that a person’s social and economic position in society greatly influences their health and well-being. The higher your place on the socioeconomic ladder – which takes into account income, wealth, education, occupation, ethnicity, and where you live – the lower your risk of ill health.

Excess weight presents a relatively new threat to health equity. In Australia, the prevalence of obesity is almost double among those living in the most disadvantaged neighbourhoods, compared with those living in the wealthiest areas.

Level of education also has a strong correlation with rates of obesity. Our analysis of weight gain among Australian adults, published on Friday in the Australian New Zealand Journal of Public Health, found that in 2000, the prevalence of obesity was just 14% among those with a degree qualification. This rose to 20% for those with a diploma, and 23% for those who had only completed high school.

Five-year weight gain followed a similar socioeconomic pattern. Between 2000 to 2005, those with a lower level of education were 30% more likely to become overweight and twice as likely to become obese, compared to those with a degree qualification.

Projecting these unequal trends in weight gain forward, we estimate that one in three Australian adults with a degree qualification will be obese by 2025. For those who have only completed high school, this figure could be as high as one in two.

The implications of these projected trends are that lower socioeconomic groups will bear an even greater burden of obesity related diseases, such as diabetes and cardiovascular disease.

Why the inequity?

There are a number of potential reasons for the social disparities in weight gain. Gradients in the prevalence of obesity are mirrored by inequalities in health behaviours, including quality of diet and physical activity levels, and in the exposure to obesogenic (obesity inducing) environments.

Clearly, people make individual choices as to what they eat, how much they eat, and how much energy they expend. But these choices are made in the social, cultural and economic context within which an individual lives. The ability to pursue healthy choices can be compromised by social, financial, and physical pressures. And these pressures increase as a person’s socioeconomic position decreases.

Research confirms that the proportion of income needed to buy a basket of healthy food is approximately three- to four-times greater for those on a low income than it is for high-income earners. On the other hand, high energy diets are generally associated with lower costs, making them more affordable to lower-income groups.

Individual or population-wide targets?

Internationally, governments are making a creditable effort to prevent further increases in obesity. Recent examples include a “fat tax” in Denmark and the proposed banning of “super-sized” sugary drinks in New York. But there has been little analysis about the potential impact of these strategies on different socioeconomic groups.

Whether an obesity intervention is targeted at individual behaviour, at the population level, or somewhere between the two, it’s important to consider the potential effect across the entire social gradient. Once implemented, ongoing evaluations should monitor the health-equity impact to ensure that the policy itself doesn’t widen the social divide in obesity prevalence.

Some obesity prevention strategies may be more effective among those with a higher socioeconomic position, widening the difference between social strata. Interventions that focus solely on information and knowledge, and require a high level of behaviour change, for example, are likely to be of greater benefit to those from more socioeconomically advantaged backgrounds.

Conversely, population approaches to prevention, which alter the environment in which we live to encourage a healthy lifestyle, are more likely to benefit all members of the population more equally. We saw this with Australia’s population-based tobacco control strategies. Clean indoor air laws and increasing the price of tobacco products had an equal or greater effect among lower-income adults.

Getting our priorities right

If we don’t act to narrow the social gradient of obesity, we’re likely to see a widening of health inequalities over the coming decades. But to address the problem effectively, we need to systematically consider the effects of obesity prevention policy across all sub-groups of the population.

Levelling life’s playing field so that everyone has the same opportunity to make healthy choices must be regarded as a political health priority.

This is part nine of our series Obese Nation. To read the other instalments, follow the links below:

Part one: Mapping Australia’s collective weight gain

Part two: Explainer: overweight, obese, BMI – what does it all mean?

Part three: Explainer: how does excess weight cause disease?

Part four: Recipe for disaster: creating a food supply to suit the appetite

Part five: What’s economic growth got to do with expanding waistlines?

Part six: Preventing weight gain: the dilemma of effective regulation

Part seven: Filling the regulatory gap in chronic disease prevention

Part eight: Why a fat tax is not enough to tackle the obesity problem

Part ten: Innovative strategies needed to address Indigenous obesity

Part eleven: Two books, one big issue: Why Calories Count and Weighing In

Part twelve: Putting health at the heart of sustainability policy

Part thirteen: Want to stop the obesity epidemic? Let’s get moving

Part fourteen: Fat of the land: how urban design can help curb obesity

Part fifteen: Industry-sponsored self-regulation: it’s just not cricket

Part sixteen: Regulation and legislation as tools in the battle against obesity