Technical Paper 1:
Obesity in Australia: a need for urgent action

3. New studies on the impact of obesity

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There is some evidence that more recently born generations are at greater risk of becoming overweight and obese. A study on the ‘Age, period and birth cohort effects on prevalence of overweight and obesity in Australian adults from 1990 to 2000¹ examined the effects of age (20 to 74 years and over), survey period (1990, 1995 and 2000) and birth cohort (in five-year periods from 1915 and earlier to 1976–80) on the prevalence of self-reported overweight and obesity in Australian adults between 1990 and 2000.The prevalence of combined overweight/obesity increased with age, recency of survey period and with cohorts born since 1960. While most of the findings were demonstrated for both men and women, for overweight/obesity combined the overall effect of birth cohort was significant among women but not men.[22]

There is increasing evidence of comorbidities associated with overweight and obesity. A recent study found that both overweight and obesity are associated with the incidence of multiple comorbidities, including type II diabetes, cancer and cardiovascular diseases. Maintenance of a healthy weight could be important in the prevention of the large disease burden in the future.[23]

A review of recent data on the prevalence, severity and racial/ethnic differences in childhood obesity found obesity to be associated with significant health problems in the paediatric age group and to be an important early risk factor for much of adult morbidity and mortality. The authors noted that many obese children and adolescents already manifest some metabolic complications, and that these children are at high risk for the development of early morbidity.[24]

Obesity and life expectancy

A range of studies indicate a link between life expectancy and overweight and obesity prevalence. For example, estimates based on Australian data indicate that life expectancy at age 20 is about one year less among overweight Australian adults compared with Australians within the healthy weight range, and an average of around four years lower for obese Australian adults. The largest ever investigation of how obesity affects mortality analysed the link between weight and longevity in nearly 900,000 people internationally, and found that moderately obese people (BMI of between 30 and 35) died 2–4 years earlier than those with an ideal weight. A BMI of 40–45 reduced life expectancy by 8–10 years, comparable with the effects of lifelong smoking.[25] Similarly, other research estimating the impact of obesity on life (from age 40) found a mean loss of seven years associated with obesity – similar to the life expectancy loss from smoking.[26]

Recent work commissioned by the Taskforce indicates that if current trends in overweight and obesity continue, there will be approximately 1.75 million deaths at ages 20+ years and 10.3 million premature years of life lost (PYLL)1 at ages 20–74 years caused by overweight/obesity in Australia in 2011 to 2050.[27] Each Australian aged 20–74 years who dies from overweight/ obesity in 2011 to 2050 will lose, on average, 12 years of life before the age of 75 years.
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Stopping the increase would save half a million lives: if current trends are halted and overweight/obesity levels are stabilised at 2005 levels, there will be around 1.25 million deaths at ages 20+ years. For each additional 1% proportional reduction in overweight/obesity that can be achieved beyond a stabilisation at 2005 prevalences, around an additional 10,000 deaths and 60,000 PYLL will be prevented.[27]

Obesity and diabetes

Obesity has been disproportionately prevalent among women and minorities, accompanied by an increased risk for diabetes mellitus (DM). Women have experienced an increased risk for metabolic syndrome, DM and cardiovascular disease after onset of menopause. Maternal obesity has been a risk factor for gestational diabetes mellitus (GDM). Obesity and DM represent crises for the healthcare system and the health of the public, incurring costs and disease burden for adults and children, with increasing costs and prevalence expected unless more coordinated efforts to address the causes of these conditions at the national level are implemented. An investment in infrastructure to promote increased physical activity and reward weight management may be budget neutral in the long term by reducing the costs of morbidity and mortality. About two-thirds of the costs from DM complications could be averted with appropriate primary care.[28]

Obesity and cancer risk

In November 2007, the ‘Second Expert Report on Food, Nutrition, Physical Activity and the Prevention of Cancer: A global perspective’ was launched. This is the most current and comprehensive analysis of the literature on diet, physical activity and cancer, building on the foundation established by the World Cancer Research Fund International (WCRF) in the 1980s to analyse, interpret and make public the available scientific evidence to help individuals reduce their risk of developing cancer. The Second Expert Report was commissioned and funded by the WCRF and the American Institute for Cancer Research (AICR), with the content driven by an independent panel of 21 world-renowned scientists.[29]

The main focus of the Second Expert Report is on nutritional and other biological and associated factors that modify the risk of cancer. However, it was recognised that the risk of cancer and other diseases is also modified by social, cultural, economic and ecological factors. That is, the food and drink that people consume are not purely because of personal choice, and similarly opportunities for physical activity can be constrained.

For this reason, a companion report, ‘Policy and Action for Cancer Prevention’, was published in February 2009,[30] which identifies a wider range of policy recommendations and options. This report provides advice and guidance on what can be done to influence and change the lifestyle choices that people make, as they relate to their risk of cancer. The report sets out changes that can be made at all levels of society to reduce the number of cancer cases.
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The Expert Report concludes that there is convincing evidence that excess body fat increases risk of cancers of the bowel, oesophagus, pancreas, kidney, endometrium and breast (in postmenopausal women). Being overweight also probably increases the risk of gallbladder cancer. The report recommends being as lean as possible within the normal range of body weight across the life course, and cites maintenance of a healthy weight throughout life as possibly one of the most important ways to protect against cancer. Being physically active as part of everyday life is recommended, as all forms of physical activity protect against some cancers, as well as against weight gain, overweight and obesity. Correspondingly, sedentary ways of life are a cause of these cancers and of weight gain, overweight and obesity. Weight gain, overweight and obesity are also causes of some cancers independently of the level of physical activity.

The Expert Report[29] recommends limiting the consumption of energy-dense foods and avoiding sugary drinks, with the main purpose of the recommendation to prevent and to control weight gain, overweight and obesity. The evidence shows that it is not specific dietary constituents that are problematic, so much as the contribution these make to the energy density of diets. The report also recommends eating mostly foods of plant origin, and that these probably protect against weight gain as they are typically low in energy density. Other recommendations include limiting intake of red meat and salt, and avoiding processed meat.

The recommendations contained in the companion report[30] included the following statements:


Action is needed:

‘Incidence and trends of cancer, and of obesity – a cause of a number of cancers – now amount to a global public health crisis. While there is more to be learned about the causes of cancer and of obesity, enough is known to justify policies and actions at all levels from international to personal.’

The public health approach:

‘Public health is a public good, requiring protection that needs leadership and concerted and determined action across many sectors taken at all levels. Citizens have a right to expect that decisions determining availability of foods and drinks and opportunities for physical activity in any societal sector are taken with public health as a top priority.’
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Women and weight gain

Women aged 25–45 years represent a high risk group for weight gain, and those with children are at increased risk because of weight gain associated with pregnancy and subsequent lifestyle change. An Australian study investigated the baseline weight-related behaviours and feasibility of recruiting and delivering a low-intensity self-management lifestyle intervention to community-based women with children in order to prevent weight gain, compared to standard education.

The recruitment and delivery of the cluster-randomised controlled intervention was in conjunction with 12 primary (elementary) schools. Nearly all women (90%) reported being dissatisfied with their weight and 72% attempted to self-manage their weight. The women were more confident of changing their diet (mean score 3.2) than physical activity (mean score 2.7). This population perceived they were engaging in prevention behaviours, with 71% reporting actively trying to prevent weight gain, yet they consumed a mean of 68g fat per day (SD30g) and 27g saturated fat per day (SD12g), representing 32% and 13% of energy respectively. The women had a high rate of dyslipidemia (33%) and engaged in an average of 9187 steps per day (SD 3671).

The study concluded that delivery of a low-intensity intervention to a broad cross-section of community-based women with children is feasible. Women with children are engaging in lifestyle behaviours which do not confer adequate health benefits. They appear to be motivated to attend prevention programs by their interest in weight management. Interventions are required to strengthen and sustain current attempts at achieving healthy lifestyle behaviours in women to prevent weight gain.[31]

While physical activity is important for the health of all individuals, the determinants of physical activity behaviour for women who are overweight remain largely unexplored. A preliminary analysis of barriers, intentions and attitudes towards moderate physical activity in a small group of overweight women explored a range of factors influencing participation in physical activity for the women.[32] The 30 participants were aged 25–71 years, with a mean age of 46.8 years and an average BMI of 31.2 (+5.6). Self-reported level of physical activity, perceived barriers and facilitators of physical activity, attitudes, intentions and perceived behavioural control to physical activity were measured.
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Seventeen participants were generally active, with self-reported moderate physical activity of 218.53 minutes in the last seven days, whereas 13 participants reported being less active (43.46 minutes). Active participants were more likely to identify social reasons for participating in physical activity, while inactive participants perceived that their laziness prevented them from being physically active. There were no significant differences between active and inactive overweight women in attitude, intention or subjective norm for moderate-intensity physical activity. There was a significant difference between these women in perceived behavioural control for moderate-intensity physical activity: women who felt more in control
of their physical activity behaviour were more likely to engage in physical activity than inactive women.

The authors concluded that future research should investigate interventions to increase behavioural control of moderate-intensity physical activity in women who are overweight.[32]

¹The person-years of life lost as a result of exposure of the population to a particular condition, in this case overweight/obesity.

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