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OVERWEIGHT/ OBESITY (SELF-REPORTED BODY MASS INDEX) (a)(b), Age standardised (c), 18 years and over
OVERWEIGHT AND OBESITY
In 2007-08, a higher proportion of males aged 18 years and over were overweight or obese (63%) than were females (48%). These overweight/obesity rates were both up five percentage points on the 2001 results. These estimates are based on people's self reported height and weight.
People being overweight or obese may have significant health, social and economic impacts, and is closely related to lack of exercise and to diet. Being overweight or obese increases the risk of suffering from a range of health conditions, including coronary heart disease, Type 2 diabetes, some cancers, knee and hip problems, and sleep apnoea. (Endnote 1) In 2008, the total annual cost of obesity to Australia, including health system costs, loss of productivity costs and carers' costs, was estimated at around $58 billion. (Endnote 2)
While genetics may play a role in a person's propensity to become overweight or obese, the fundamental cause is an imbalance between energy consumed and energy expended. Shifts towards energy-dense diets and decreasing physical activity are two of the factors that have contributed to increases in rates of overweight and obesity. (Endnote 3)
Over the last two decades, there has been a steady shift in the Australian population towards the higher end of the Body Mass Index (BMI), driven mainly by weight gain rather than by changes in height. The BMI, a simple index of weight for height, is commonly used to classify people as overweight and obese. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m2).
In general, rates of overweight/obesity are higher in older age groups, although males and females in the oldest age group (75 years and over) had lower rates. Adult male overweight/obesity rates are higher than female rates across all age groups. In 2007-08, 73% of males in the 65-74 year age group were overweight or obese compared to 39% in the 18-24 year age group. There has been a 10 percentage point increase in the 65-74 year age group male overweight/obesity rate since 2001 when 63% of males in this age group were overweight or obese.
The highest overweight/obesity rate for females in 2007-08 was in the 55-64 year age group (61%), while the lowest rate was in the 18-24 year age group (29%). Since 2001 the proportion of females who were overweight or obese increased for all age groups, with the highest increases occurring in the 18-24, 25-34 and 35-44 year age groups (each up by seven percentage points).
Measured Body Mass Index
In the 2007-08 National Health Survey (NHS), the measured height and weight of respondents was collected in addition to their self reported information. Based on measured data, 68% of males and 55% of females aged 18 years and over were either overweight or obese (compared to rates of 63% and 48% based the self reported height/weight).
Males and females had similar rates of obesity (26% and 24% respectively), but a higher proportion of males (42%) were overweight than were females (31%). This result may be influenced by the fact that males generally have more muscle mass than females. For males and for females the 65-74 years age group recorded the highest rates of overweight/obesity (79% and 71% respectively).
Measured BMI data from the 2007-08 NHS may be compared with measured BMI data from the 1995 National Nutrition Survey to see how the overweight/obesity rates have changed over the that time. While the proportion of males who were overweight or obese has increased by four percentage points, it has increased by six percentage points for females. These increases have been more at the obese end of the BMI scale, with obesity rates increasing by seven percentage points for males and five percentage points for females over this period.
While being overweight or obese is more prevalent in middle to late adulthood, Australia's increasing obesity is evident in the large numbers of younger people who are now overweight or obese. In 2007-08, 62% of males and 44% of females aged 25-34 years were overweight or obese.
Overweight and obesity in children is a major health concern. Studies have shown that once children become obese they are more likely to stay obese into adulthood and have an increased risk of developing both short and long-term health conditions, such as Type 2 diabetes and cardiovascular disease. (Endnote 4)
In 2007-08, a quarter of all Australian children aged 5-17 years, were overweight or obese. This was up four percentage points from 21% in 1995. The proportions of boys and girls who were overweight or obese were similar (26% and 24% respectively). Between 1995 and 2007-08, there was no change in the proportion of boys who were overweight (16%) but the proportion of boys who were obese almost doubled from 5% in 1995 to 9% in 2007-08. The increase in the proportion of boys who were obese was higher in the 13-17 year age group (up seven percentage points) compared to the 5-12 year age group (up four percentage points).
The obesity rate for girls aged 5-17 years remained unchanged at 6% during this period, while the proportion of girls who were overweight increased by three percentage points. The increase in the proportion of girls who were overweight occurred for older girls only (13-17 years), up from 12% in 1995 to 20% in 2007-08.
Overweight and obesity in Aboriginal and Torres Strait Islander peoples
In 2004-05, 62% of Aboriginal and Torres Strait Islander males and 58% of Aboriginal and Torres Strait Islander females aged 18 years and over were overweight or obese. For both Aboriginal and Torres Strait Islander males and females, the rates for overweight/obesity were higher in older age groups, with nearly three quarters of both the male and female populations aged 55 years and over being overweight or obese.
1. Australian Bureau of Statistics, 2010, Measures of Australia's Progress, 2010 (cat. no. 1370.0) <www.abs.gov.au>.
2. Access Economics, 2008, The Growing Cost of Obesity in 2008: Three Years On, Diabetes Australia, Canberra.
3. Australian Bureau of Statistics, 2009, Australian Social Trends, Dec 2009 (cat. no. 4102.0) <www.abs.gov.au>.
4. Australian Bureau of Statistics, 2009, Australian Social Trends, Sep 2009 (cat. no. 4102.0) <www.abs.gov.au>.
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