- 1 Impact of obesity and related risk factors on cancer in Australia
- 2 Broader health and social impacts
- 3 Prevalence of obesity and overweight in Australia
- 4 How physically active are Australians?
- 5 What are Australians eating?
- 6 References
Overweight and obesity, and the underlying factors of physical inactivity and poor nutrition are responsible for a significant percentage of the cancer burden in Australia. In 2011, physical inactivity accounted for 6.4% of the total cancer burden, high body mass for 4.5% and low fruit consumption for 2.6%. Overlaps in these risk factors make it difficult quantify their total impact on cancer burden. For example, physical inactivity and low fruit and vegetable consumption are individual cancer risk factors, but they also contribute to high body mass, which is a separate risk factor.
An estimated 3,917 cancer cases (3.4% of all cancers) diagnosed in 2010 were attributable to overweight/obesity(see Table 1 below). It was estimated that 1.6% of the cancer burden in Australia in 2010 was due to insufficient levels of physical activity, 1.4% and 0.3% due to low fruit and vegetable intake respectively .
Table 1. Population attributable fraction (PAF) for males and females and estimated number of cancers diagnosed in Australia in 2010 attributable to overweight and obesity
|Site||Males||Females||Total number of cancers|
|Breast in women||6.8||971|
In 2008, it was estimated that the health system cost of cancers linked to obesity was approximately $190 million; the overall cost to the broader economy, including productivity losses, was put at $9.7 billion. The direct health costs for cancers attributable to physical inactivity was estimated to be $111 million in 2008. Recent estimates on the economic impact of cancers linked to poor nutrition are not available, but a 2001 Australian study found that the total healthcare costs associated with low fruit and vegetable consumption and high consumption of red and processed meats was $97 million.
Another study, analysing follow-up data from the Australian Diabetes, Obesity and Lifestyle study used a 'bottom-up approach' to calculate the direct cost to individuals due to obesity and overweight. Extrapolation of these costs to determine the cost of overweight and obesity in Australia indicated that the annual direct excess cost of overweight and obesity to Australians aged 30 and over in 2005 was $10.7 billion. This figure represents the excess direct medical and non-medical costs due to overweight and obesity, compared to those costs incurred by individuals of normal weight.
Overweight and obesity accounted for 5.5% of Australia’s total burden of disease and injury, a measure of the amount of healthy life lost due to premature death, illness and injury in 2010.
Overweight and obesity are set to overtake tobacco as the number one cause of preventable disease burden in Australia. While declines in smoking rates over recent years should lead to reductions in tobacco-caused disease, the full impact of escalating obesity rates in Australia on health outcomes is yet to be realised.
Obesity alone (not including overweight) has been estimated to cost Australia $58.2 billion each year, including direct financial costs.
Physical inactivity is a cause of obesity and overweight. It is also an independent risk factor for some cancers and for other chronic diseases such as heart disease, stroke and type 2 diabetes. The disease burden attributable to physical inactivity was estimated to be 5.0% of the total burden in Australia in 2010. In 2008, an estimated 16,178 Australian deaths were attributable to physical inactivity. The total economic cost of physical inactivity was estimated to be $13.8bn in 2008.
Poor diet is also a major cause of disease burden in Australia, as well as contributing to obesity and overweight. Low fruit and vegetable consumption accounted for 2.6 and 0.5% of the burden of disease in Australia in 2010.
Prevalence of obesity and overweight in Australia
Research has confirmed that weight gain across the population is not just a result of ageing, but that younger people are gaining weight faster than previous generations. As a result, significantly more Australians weigh more than previous generations as they reach adulthood.
Based on recent trends, if effective interventions are not put in place it is estimated that 6.9 million Australians will be obese by 2025.
Adult obesity rates in Australia have nearly tripled in the last 30 years. Measured BMI data show that in 1980, fewer than one in 10 Australian adults were obese, rising to 27.5% in 2011–12. Australia’s adult obesity rate is the fifth highest among OECD countries after the US, Chile, Mexico and New Zealand.
In 2011–12, more than one third of Australian adults were overweight in addition to the more than one in four who were obese. In total, 63% of Australian adults were overweight or obese (35.3% overweight and 27.5% obese). More more men were overweight or obese than women (69.7% compared with 55.7%).
Proportionally more women living in areas of most disadvantage are overweight or obese (63.8%) compared with women living in areas of least disadvantage (47.7%), however this pattern is not observed for men. Overweight and obesity are also more common in regional areas of Australia than in major cities.
The combined prevalence of overweight and obesity in Australian children doubled from the mid-1980s to the mid-1990s; rates of obesity trebled. Since then levels have continued to increase, but at a slower rate.
The 2007 Australian National Children’s Nutrition and Physical Activity Survey found that 23% of children aged 2–16 years of age were overweight or obese (17% overweight; 6% obese). Overweight and obesity rates were highest among children aged 9–13 years (girls 30%; boys 25%).
Similar findings from a national survey in 2009–10 found that 23.4% of Australian secondary school students were overweight (18.4%) or obese (5%).
NSW data indicates that the prevalence of overweight is higher in children of lower socioeconomic status, and children are more likely to be overweight if they come from a Middle Eastern background.
Obesity in childhood significantly increases the risk of being obese in adulthood and the risk of developing premature chronic disease as a result. According to the US Surgeon General, about half of children who are overweight will remain overweight in adulthood; 70% of those who are overweight by adolescence will remain overweight as adults. More conservative estimates suggests that around 25–50% of obese adolescents remain obese in adulthood. Regardless, the longer obesity persists into adolescence and the more obese the child, the more likely they will continue to be obese in adulthood.
Children and adolescents who are overweight or obese already display the markers of adult chronic diseases, such as cardiovascular disease, type 2 diabetes and fatty liver disease.
The 2012–13 Australian Aboriginal and Torres Strait Islander Health Survey reported BMI data based on collected height and weight measurements. In comparison, the National Aboriginal and Torres Strait Islander Health Survey and National Health Survey present BMI data mainly based on self-reported height and weight.
The 2012–13 Australian Aboriginal and Torres Strait Islander Health Survey reported that two-thirds (66%) of Aboriginal and Torres Strait Islander people aged 15 years and over were overweight or obese (29% and 37% respectively), according to their BMI.
While the combined overweight/obesity rates for Aboriginal and Torres Strait Islander people aged 15 years and over are similar to those for non-Indigenous people, the obesity rates are significantly higher in this population. Aboriginal and Torres Strait Islander people are 1.5 times as likely as non-Indigenous people to be obese (after adjusting for differences in age structure between the two populations). This difference is more marked in women.
The 2012–13 Australian Aboriginal and Torres Strait Islander Health Survey reported that close to a third (30%) of Aboriginal and Torres Strait Islanders children aged 2–14 were overweight or obese (20% and 10% respectively), according to measured BMI. Aboriginal and Torres Strait Islander children aged 2–14 years are 1.2 times as likely to be overweight/obese as non-Indigenous children.
How physically active are Australians?
Physical inactivity is a significant cancer risk factor, both independently and as a contributor to high body mass. The level of physical activity undertaken by Australians is therefore important in the context of the nation's cancer disease burden. Physical activity levels in relation to health benefit are measured according to an evidence-based framework.
The majority of Australian adults are not physically active enough to gain a health benefit.
The 2011–2012 Australian Health Survey found that adults spent an average of 33 minutes per day doing physical activity, yet 60% adults reported doing less than 30 minutes. According to the survey, 43% of adults were "sufficiently active" according to the Physical Activity Guidelines' threshold of 150 minutes of physical activity over five or more sessions per week. The remainder of adults were classed as insufficiently active (36%) or inactive (20%).
According to the National Health Survey 2007–2008, 73% of Australians aged 15 years and over were 'sedentary' (did very little exercise) or exercised at only low levels. This proportion had increased from 69% in 2001. Walking was the most commonly reported activity among Australians, with 48% participating, while 36% participated in moderate exercise and 15% exercised vigorously. Females were more likely to walk for exercise, while men were more likely to do moderate and vigorous exercise.
Participation in sport and physical recreation is lower among Australians born in non-English speaking countries and lower income households. People living in areas of greatest disadvantage are less likely to be sufficiently active (34%) compared with those living in areas of least disadvantage (52%).
Physical activity levels are also lower among Indigenous Australians. After adjusting for differences in age, approximately 78% of Indigenous Australians living in non-remote areas report sedentary or low exercise levels compared with 69% of non-Indigenous Australians.
According to the Australian Health Survey 2011–2012, 84% of 2–4 year olds averaged three or more hours of physical activity per day. However, just under three-quarters (72%) were physically active for three hours or more per day on all seven days prior to the survey, meeting physical activity recommendations. Among children aged 5–17 years, just over 60% averaged at least one hour of physical activity per day. Around one in five (19%) met the recommended 60 minutes per day across all seven days prior to the survey and almost half (48%) met the recommendation on at least five out of seven days. In general, physical activity decreased with age.
A national survey of children and adolescents conducted in 2007 found that 69% of boys and girls aged 9–16 accumulated at least 60 minutes of moderate to vigorous physical activity on most days, but only 32% met the guidelines every day. Girls met the guidelines less often than boys and levels dropped with age, especially for girls.
A national survey of Australian secondary school students in 2009–10 found that although most students were active, 85% were not active enough to gain a health benefit. Female students were less likely than male students to meet physical activity recommendations. The survey also found most students exceeded the recommended two-hour per day maximum use of electronic media for entertainment. On an average school day, 71% of students exceeded the recommendation, while 83% exceeded it on weekends, especially boys.
The 2012–13 Australian Aboriginal and Torres Strait Islander Health Survey reported data on the level of physical activity among Indigenous Australians aged 18 years and over living in non-remote areas only.
The survey reported that three in five (62%) respondents reported that they were physically inactive (sedentary or had exercised at a low level) in the week before the survey. Just over one-quarter (28%) Aboriginal and Torres Strait Islander adults had exercised at a moderate level, and one in ten (10%) at a high level.
Just under half (46%) the respondents had met the National Physical Activity Guidelines target of 30 minutes of moderate intensity physical activity on most days.
Aboriginal and Torres Strait Islander men were more likely to exercise than women.
Compared with non-Indigenous Australians, Aboriginal and Torres Strait Islander adults were more likely to be sedentary or to exercise at low intensity, less likely to participate in high intensity exercise and less likely to meet physical activity guidelines.
What are Australians eating?
Poor nutrition is a risk factor for cancer, particularly the impact of an unhealthy diet on obesity and overweight – which can cause cancers of the oesophagus, pancreas, bowel, breast (postmenopausal), endometrium and kidney.
Excessive consumption of particular foods such as red and processed meats can also be a risk factor for cancer, independently of weight gain and retention. A diet rich in vegetables and fruit may protect against certain cancers. See the Links section for more details.
The 2011–2012 National Nutrition and Physical Activity Survey (NNPAS) collected detailed self-reported nutrition information from over 12,000 participants across Australia. The NNPAS is the first national nutrition survey of Australian adults and children conducted in over 15 years.
The 2011–2012 NNPAS found that, while 75% of Australians report eating vegetables, only 6.8% consumed the recommended usual intake of vegetables. The group least likely to eat the recommended number of serves of vegetables was men aged 19–30 years (1.6%). Just over half (54%) of Australians consumed the recommended serves of fruit with females (58%) more likely than males (50%) to meet the recommendation.
These statistics mirror results from the National Health Survey which found that in 2007–08, 93% of Australian adults did not consume the two serves of fruit and five serves of vegetables per day recommended in the NHMRC Dietary Guidelines for Australian Adults. While one in two Australians consumed sufficient fruit, only 9% of adults consumed enough vegetables.
In 2011–2012 the self-reported average energy intake per day was 9,655 kJ for males and 7,402 kJ for females, however it is noted that this is likely to be an under-estimate due to inherent under-reporting biases with dietary surveys. On average, carbohydrates contributed the majority of total energy intake (45%), followed by fats (31%), protein (18%), alcohol (3.4%) and dietary fibre (2.2%).
Alcohol is a risk factor for weight gain and for cancer. See the Alcohol chapter of the National Cancer Prevention Policy for information on levels of consumption of alcohol in Australia.
The 2011–2012 NNPAS found that children aged 2–3 years were the age group most likely to meet requirements, however only half (49%) usually consume the recommended number of servings per day. Children aged 2–8 years had the highest rate of fruit consumption and were most likely to met daily requirements for fruit consumption.
This mirrors earlier data showing that vegetable consumption was highest among children ages 4–8 years, with 22% of children in this age group meeting consumption levels recommended in the NHMRC dietary guidelines. And data showing that fruit and vegetable consumption drops steeply in older children.
Earlier research by the Commonwealth Scientific Industrial Research Organisation (CSIRO) found that only 16–22% of children met the recommendation to limit saturated fat to less than 10% of total energy intake, while only 21–39% met the recommendation to limit intake from sugars to less than 20% of total energy intake. Consumption of sodium (salt) exceeds the recommended upper levels in all age groups.
According to self-reported data in the 2012–2013 Australian Aboriginal and Torres Strait Islander Health Survey, only one in 20 (5%) Aboriginal and Torres Strait Islander people aged 15 years and over reported eating an adequate amount (5–6 serves) of vegetables each day. This was not significantly different to the proportion of non-Indigenous Australians eating an adequate amount of vegetables.
Less than half (43%) reported eating an adequate amount (two serves) of fruit each day. This proportion was slightly less than that of non-Indigenous Australians. Data from 2008 shows that Indigenous Australians aged 12 years and over are twice as likely to consume no fruit on a typical day (13.2% cf to 6.6%) and seven times as likely to report no usual daily vegetable consumption (5.3% cf to 0.8%) as non-Indigenous persons of the same age.
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