If you're an adult in Australia, odds are you're overweight or obese.

At last count, two in three of us over the age of 18 are.

But that sobering statistic might come as a surprise to those in inner-city Perth or on Sydney's upper north shore — if they go by who they can see around them.

Just over 14 per cent of people in Sydney's Ku-ring-gai council area are obese. As a community, it has one of the leanest waistlines in the country.

Drive four-and-half hours north west to Wellington in regional New South Wales, however, and it's a different picture entirely.

There, like many other parts of outer-metropolitan and regional Australia, nearly half the adult population is obese, putting them at higher risk of diabetes, some cancers, heart disease and dementia.

On World Obesity Day, an Australian researcher is calling for a reset on how we tackle the issue.

"We are becoming a fat and inactive nation … and it's almost entirely where you live that counts," says Rosemary Calder, professor of health policy at Victoria University (VU).

According to VU's Australian Health Tracker, obesity rates across Australia are hugely dependent on where people live, and vary between regions by as much as 300 per cent.

"The proportion of people who are obese has risen 27 per cent in 10 years," Professor Calder said.

"We cannot ignore the influence of where people live — and where people live has a lot to do with their socio-economic status."

Professor Calder argued urgent action was needed to tackle Australia's burgeoning obesity epidemic where it matters most: among the country's most disadvantaged communities.

"Obesity is an issue of place," she said.

"We need governments to understand the best way to improve the nation's health is to really focus on the communities where health is at greatest risk."

Wealthy communities, smaller waistlines

In Australia, central Melbourne and Perth, as well as a handful of inner-city West Australian suburbs, top the league table of least overweight or least obese communities.

Wealthy city suburbs typically have the lowest rates of obesity because they are the most well-resourced, Professor Calder said.

"These suburbs are usually green and leafy, with more space dedicated to parks, gardens and recreational facilities," she said.

"They often are well serviced by public transport, bike paths and are relatively close to where people work, which enables people to be physically active in their commute to work, rather than rely on the car."

A greater density of shops selling fresh fruit and vegetables and fewer fast food outlets also means accessing healthy food is easier.

"People in our wealthier suburbs tend to have better access to information about healthy diet and the financial means to access healthy food options."

In contrast, lower socio-economic areas, which are often new outer-metropolitan suburbs or regional communities, seldom have physical infrastructure that supports healthy lifestyles.

"Low income suburbs rarely have any of that, and if they do, they are highly dependent on cars, because of usually much less public transport," Professor Calder said.

"They have a much higher rate of fast food outlets, much lower access to speciality fresh food outlets."

Obesity not a choice, experts say

With this in mind, Professor Calder said it is time we stopped framing obesity as a problem of personal responsibility.

"We have spent too long as a nation expecting individuals to be able to change their behaviour to reduce their weight," she added.

"The evidence is very clear that this has little chance of success without a very strong focus on the environmental factors in the places where we live that contribute to poor nutrition and inactivity.

"We have to realise that individuals cannot make good choices when those good choices are not available to them, either because of their resources, or because of the resources in their community."

According to the ABC's Australia Talks national survey, nearly a third of Australians have trouble making ends meet.

For Australians living on a low income, or in poverty, fast food is often the cheapest, most feasible food option, Professor Calder said.

"If you're a single parent with several children, it's going to be easier to feed your family a large serving of chips than it is to go and do a meal with vegetables and meat.

"Your choices are driven by your resources … not by what's good for you."

Fast foods are a cheap and easy option, and sometimes the only option in lower-income suburbs. ( Pixabay )

Jane Martin, executive manager of the Obesity Policy Coalition, agreed, and said although obesity is a population-wide problem, there needed to be a focus on low-income communities.

"It's not easy when you've got plenty of resources and are well educated," Ms Martin said, "it's a lot harder when you don't have the resources, money or skills."

In her view, dismissing obesity as a personal problem for people to manage, or attributing blame to individuals, wasn't going to solve the problem.

"The solution does not lie with individual. It's much greater than that."

'Community responsibility, not individual responsibility'

In June, Federal Health Minister Greg Hunt established plans for a National Preventative Health Strategy, which will include a focus on nutrition and obesity.

Professor Calder said this is a "step in the right direction" — so long as the government considers the impact of where people live on their health.

She said places with the highest rates of obesity also had higher rates of smoking, physical inactivity and chronic illness, and were largely low-socioeconomic communities, highlighting the impact of poverty on all aspects of health.

"We have children entering schools in parts of Australia that don't know what an apple is until they go to school.

"We have to change that. And we have to change it as a community responsibility, not an individual responsibility."

In addition to creating environments that promote healthy eating and physical activity, Professor Calder said Australia needs to look more closely at its policies around salt and sugar content in processed foods.

Ms Martin suggested that stricter regulations around food labelling and junk-food advertising are also needed.

"Young people are heavily targeted through price promotion and the advertising of unhealthy foods," she said.

"It's outrageous that there's not more oversight."

Tackling the obesity epidemic, she said, requires effective action beyond targeted-health interventions.

"Affordable housing and education are really important precursors for good health," Ms Martin said.

"Many people are struggling to make ends meet … and suffering poor health as a result."

The Federal Government's first National Obesity Strategy is in development and expected to be presented to the COAG Health Council in June 2020.