eMJA: Baur, Obesity: definitely a growing concern

Editorial

Obesity: definitely a growing concern

Time to implement Australia's strategy for preventing overweight and obesity

MJA 2001; 174: 553-554

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Obesity is increasingly recognised as a health problem by the Australian community, with frequent discussions of obesity-related issues in the media and heavy marketing of weight-loss products. There is abundant evidence to support this view, not least being the 1995 National Nutrition Survey showing that 56% of adult Australians are either overweight or obese.¹

A casual observer at a shopping mall or a school playground might also note that obesity is common among the younger members of our community, and, in this issue of the Journal, Magarey and colleagues show that this is indeed the case.² They compared Australian childhood data with a newly developed international definition of childhood overweight and obesity.³


	. . . we need to better understand the potent forces promoting the development of obesity . . .

To understand their results, it is worth looking first at how overweight and obesity are measured. Body mass index (BMI; weight in kilograms/height in metres squared) is widely used as a measure of percentage body fat, both at the population level as well as in clinical practice. BMI is significantly correlated with percentage body fat and is also specific for those with the greatest amount of body fat.^4,5 For adults there are internationally recognised and easily remembered cut-off points for defining health risk according to BMI: a BMI of 25 kg/m² for overweight and of 30 kg/m² for obesity.⁶ However, in childhood, BMI varies with age and sex. It rises during the first year, then falls during the preschool years, before rising once more into adulthood. For this reason, BMI in childhood and adolescence is assessed using age-related reference values.

Until recently, there has been a lack of agreement about the definition of overweight and obesity in childhood and adolescence, with only arbitrary cut-off points being used to identify childhood obesity. Then, in May 2000, the International Obesity Task Force (IOTF) Childhood Obesity Working Group published standard definitions for overweight and obesity in childhood.³ These definitions are based on a compilation of nationally representative cross-sectional growth studies from six countries. For each of the growth studies, centile curves were drawn that intersect, at age 18 years, with the cut-off points of 25 kg/m² and 30 kg/m² for adulthood overweight and obesity, respectively. While still somewhat arbitrary in comparison with the risk-related BMI ranges in adults, these cut-off points for each 6 months from 2-18 years at least allow international comparisons of the prevalence of overweight and obesity in childhood and adolescence.

Magarey and colleagues used previously gathered data on BMI from two national surveys involving Australian children and adolescents and compared these data with the new overweight and obesity definitions. The first survey they used, the 1985 Australian Health and Fitness Survey, involved schoolchildren aged 7-15 years. The second, the National Nutrition Survey, in 1995 and early 1996, was a household survey of people aged over 2 years, although, for the purposes of their analysis, only the age group 2-18 years was included. The two surveys had somewhat different sampling methods and age classifications, but Magarey et al noted that these methodological differences would not account for the prevalence rate changes they identified.

So, what is happening to the prevalence of overweight and obesity in Australian children? In 1985, the prevalence rate for overweight or obesity was 10.7% for boys and 11.8% for girls, with 1.4% of boys and 1.2% of girls being obese. Only 10 years later, depending upon age, 13.4%-26.1% of boys and 18.9%-23.5% of girls were overweight or obese, with the prevalence of obesity being 2.4%-6.8% in boys and 4.2%-6.3% in girls. Thus, over the 10 years 1985-1995, the prevalence of overweight in children aged 7-15 years has increased almost twofold, while that of obesity has more than tripled. These results are both dramatic and disturbing. They are in keeping with a study in Victoria by Lazarus et al,⁷ who compared the anthropometry of children aged 7-12 years from the 1985 Australian Health and Fitness Survey with that of similar-age children who took part in the 1997 Health of Young Victorians Study. Substantial increases in BMI were found over the 12 years between 1985 and 1997.

The results of the studies by both Magarey et al² and Lazarus et al⁷ raise a number of issues. For example, it is clear that the World Health Organization's description of "an escalating global epidemic of overweight and obesity . . . taking over many parts of the world"⁸ applies very much to Australia and Australian children and adolescents — obesity cannot be ignored. It also appears that regular monitoring is required in order to track trends in obesity prevalence to inform healthcare planning. More importantly, we need to better understand the potent forces promoting the development of obesity in the Australian community, especially among children and adolescents, because only then can we hope to effectively manage or prevent it. These forces include:

The increasing use of motor vehicles;
The rise of sedentary pursuits, such as watching television or using computers;
The ready availability of energy-dense foods and foods with a high fat content;
A move away from traditional foods and eating patterns;
Perceptions that local neighbourhoods are unsafe, because of child safety and pedestrian safety concerns;
Changes in family work patterns so that the parents are busier and may have less time to spend with their families.

Finally, the magnitude of the problem of obesity in Australia means that, to prevent further increases in prevalence, population-level strategies must be applied. Australia was the first country in the world to develop a national strategy for preventing overweight and obesity.⁹ Launched more than three years ago, this national strategy has yet to be implemented. It includes a broad range of approaches, such as creating opportunities for increasing both planned and incidental activity in community environments (safe bike paths, pedestrian-friendly environments, more public space available for recreational use); encouraging public and private sector food services (childcare centres, lunch bars, takeaway food outlets) to offer healthy food choices; and encouraging school councils to develop healthy school canteen policies. The overweight and obesity prevalence changes presented in this issue of the Journal leave no doubt that the time has come.

Louise A Baur
Associate Professor
Sydney University Department of Paediatrics and Child Health
The Children's Hospital at Westmead, Westmead, NSW

Australian Institute of Health and Welfare. Overweight. Available from: <www.aihw.gov.au/cvd/riskfactors/overweight.html> (accessed February 2001).
Magarey AM, Daniels LA, Boulton TJC. Prevalence of overweight and obesity in Australian children and adolescents: reassessment of 1985 and 1995 data against new standard worldwide definitions. Med J Aust 2001; 174: 561-564.
Cole TJ, Bellizzi MC, Flegal KM, Deitz WM. Establishing a standard definition for child overweight and obesity worldwide; international survey. BMJ 2000; 320: 1240-1243.
Roche A, Siervogel F, Chumlea W, Webb P. Grading body fatness from limited anthropometric data. Am J Clin Nutr 1981; 34: 2831-2838.
Lazarus R, Baur L, Webb K, Blyth F. Body mass index in screening for adiposity in children and adolescents: systematic evaluation using receiver operating characteristic curves. Am J Clin Nutr 1996; 63: 500-506.
World Health Organization. Obesity. Preventing and managing the global epidemic. Report of a WHO consultation on obesity. Geneva: WHO, 1998.
Lazarus R, Wake M, Hesketh K, Waters E. Change in body mass index in Australian school children 1985-1997. Int J Obesity 2000; 24: 679-684.
World Health Organization. Nutrition. Available from: <www.who.int/nut/obs.htm> (accessed February 2001).
National Health and Medical Research Council. Acting on Australia's weight. A strategic plan for the prevention of overweight and obesity. Canberra: Commonwealth Department of Health and Family Services, 1997.

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