FEATURE ARTICLE 1: CHILDREN WHO ARE OVERWEIGHT OR OBESE

Obesity is a major contributor to the global burden of chronic disease and disability. Around the world, levels of childhood obesity have been rising for a number of reasons including a shift in diet towards increased intake of foods that are high in fat and sugars and a reduction in the amount of time spent on physical activity.

Obesity not only has significant health and social impacts, but also considerable economic impacts. According to Access Economics, in 2008, the total annual cost of obesity in Australia, including health system costs and productivity and carers costs was estimated to be around $58 billion.

In 2007, the Australian Government announced the development and promotion of healthy eating and physical activity guidelines for children. These measures will form part of the Government's Plan for Early Childhood and Plan for Tackling Obesity. One of the main aims of the National Preventative Health Taskforce is to develop a National Obesity Strategy.


Changes over time

In 2007-08, one-quarter of all Australian children, or around 600,000 children aged 5-17, were overweight or obese, up four percentage points from 1995. The obesity rate for children increased from 5% in 1995 to 8% in 2007-08 (graph 11.9).

Age and sex

Between 1995 and 2007-08 there was a significant increase in the proportion of boys who were obese. The rate of obesity for boys aged 5-17 years doubled from 5% in 1995 to 10% in 2007-08. Increases in obesity occurred for younger and older boys. For boys aged 5-12 years, 8% were obese, up from 4% in 1995. Of boys aged 13-17 years, 13% were obese, up from 6% in 1995.

While for boys there were significant increases in obesity, there were no such increases for girls. The obesity rate for girls aged 5-17 remained unchanged at 6%. While the obesity rate for girls did not change from 1995 to 2007-08, the proportion of girls who were overweight increased. The increase occurred for girls aged 13-17 years, up from 12% in 1995 to 20% in 2007-08. In contrast, there was no change for younger girls aged 5-12 years, with the overweight rate remaining constant at 17% in both time periods.

Socio-economic factors

The Socio-Economic Indexes for Areas (SEIFA) Index of Disadvantage summarises various attributes such as income, unemployment and educational attainment of an area in which people live. Children living in the areas of greatest relative disadvantage had more than double the rate of obesity (28%) of children living in areas with the lowest relative disadvantage (13%). Aside from socio-economic differences between areas in terms of education, income and employment, some areas may also offer greater opportunities for physical activity and greater access to healthy food options.


Physical activity

The 2004 Australia's Physical Activity Recommendations for Children suggest that children aged 5-18 years need a minimum of 60 minutes of moderate to vigorous physical activity every day. The following section looks at physical activity using results from two ABS surveys. The 2006 Children's Participation in Culture and Leisure Activities Survey collected information on the participation of children aged 5-14 years in organised sports and informal sports during the 12 months prior to interview. It provides insight into some of the physical activities in which children aged 5-14 are participating. The 2007-08 National Health Survey collected information for children aged 15-17 only.

Children aged 5-14 years

In 2006, 63% of children had played sport which had been organised by a school, club or association outside of school hours, an increase from 59% in 2000. Over the six year period, girls' participation in organised sport rose by six percentage points from 52% to 58%, compared with three percentage points for boys from 66% to 69%. While the participation rates of about 45% were similar for children aged 5 years, by 13 years of age the participation rate for boys was 73% and for girls was 55%. The highest rate of participation for boys was at 10 years (77%), while for girls it was 9 years (67%) (graph 11.10).

Children who did participate were spending 6 hours per fortnight on average on organised sport participation. Swimming and outdoor soccer were the most popular sports. The survey also collected information on informal sports, such as bike riding, rollerblading and skateboarding, to get some indication of children's involvement in informal physical activity. The survey found that around two thirds of children had been bike riding and a quarter had been skateboarding or rollerblading in the previous two weeks. The amount of time spent on these informal activities was the same as organised sport participation, with an average of 6 hours per fortnight (graph 11.10).



Children aged 15-17 years

In 2007-08 over three-quarters of children aged 15-17 took part in sport or recreational exercise in the two weeks prior to the National Health Survey. However, just under one quarter said that they either did no exercise, or very low amounts during the two week period.


Sedentary lifestyles

According to the Department of Health and Ageing Australia's Physical Activity recommendations for children, children who do not get enough physical activity and spend significant amounts of time in sedentary states increase their likelihood of poor fitness, raised cholesterol and being overweight in adulthood. Related research has also shown that the incidence of obesity is highest among children who watch TV for long periods each day, compared with children who watch TV for a smaller amount of time each day. Australian guidelines recommend that children should not spend more than two hours a day watching TV, playing computer games or using other electronic media for entertainment.

In 2006, almost all children aged 5-14 had watched television, videos or DVDs during the two-week period of the survey and almost two-thirds had played electronic or computer games. Around 45% of children who watched television, videos or DVDs, and 10% of children who played electronic or computer games, did so for 20 hours or more over the fortnight period. Overall, the average amount of time spent on these two activities by most children averaged across a two-week period, was 2 hours per day (graph 11.10).


Data sources and definitions

The information in this article comes from the 2007-08 NHS and 2006 Children's Participation in Cultural and Leisure Activities Survey (4901.0). Physical activity results from these surveys may not represent total physical activity, since the surveys only cover sport organised by a school, club or association which has been played outside of school hours. The article looks at children aged 5-17 years unless stated otherwise. Body Mass Index (BMI) was calculated from measured height and weight information (using the formula weight (kg) divided by the square of height (m)). Height and weight were measured for children in the 2007-08 NHS. Overweight and obesity are defined according to the BMI scores, indicating a relationship between height and weight. There are BMI cutoffs for children which are based on the definitions of adult overweight and obesity adjusted to specific age and sex categories for children. For a detailed list of the cutoffs used to calculate BMI for children, please see the ABS National Health Survey Users' Guide (4363.0.55.001).

REFERENCES

World Health Organisation Global Strategy on Diet, Physical Activity and Health, Overweight and Obesity, viewed 6 July 2009.

Access Economics, The Cost of Obesity, Canberra, 2008.

Department of Health and Ageing, Early Childhood Nutrition, viewed 15 June 2009.

Australian Health Ministers Communique, Delivering Results, 18 April 2008.

Australian Institute of Health and Welfare, Making Progress, Canberra, 2008.

King, T et al. 2005, 'Weight and place; a multilevel cross sectional survey of area-level disadvantage and overweight and obesity in Australia' International Journal of Obesity, viewed 5 August 2009.

ABS Australian Social Trends, (4102.0) September 2009.

Department of Health and Ageing, Australia's Physical Activity Recommendations for children, viewed 21 May 2009.

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