How overweight, obesity and nutritional imbalance contribute to Australia's health status (VCE HHD Unit 3 AoS 1)

What this dot point is asking

The 2025 study design asks you to know "the contribution to Australia's health status of ... overweight and obesity, nutritional imbalance (under-consumption of fruit and vegetables, and dairy foods; high intake of fat, salt and sugar; low intake of fibre)". That is six specific nutritional imbalances plus overweight and obesity. For each you need a mechanism, a named condition, and a health status indicator with a direction.

The VCAA FAQ explains that students are expected to link these factors to health outcomes, and that "when examining health data, students identify the major burdens of disease in Australia, which will help frame the diseases they need to be familiar with". The major burdens that nutrition and body weight feed into are cardiovascular disease, type 2 diabetes, some cancers and musculoskeletal conditions.

Overweight and obesity

Definitions

Overweight and obesity mean excess body fat that presents a risk to health. For adults the usual measure is body mass index (BMI), weight in kilograms divided by height in metres squared:

A BMI of 25 to less than 30 is classed as overweight and 30 or more as obese. Waist circumference is also used because fat stored around the abdomen carries particular risk. For children, BMI is compared with age- and sex-specific reference values.

How much overweight and obesity is there?

How overweight and obesity affect health status

Its contribution in the burden of disease study

In the AIHW's Australian Burden of Disease Study 2024, overweight (including obesity) became the leading risk factor for burden of disease, contributing 8.3 per cent of total burden (480,827 DALY), 9.6 per cent of fatal burden and 7.1 per cent of non-fatal burden. It rose from 4th in 2003 and 2nd in 2018. The AIHW notes that the age-standardised rate of burden attributable to overweight has been relatively stable; the change in rank is mainly because tobacco-attributable burden fell 41 per cent. However, the rate of non-fatal burden attributable to overweight including obesity rose 22 per cent between 2003 and 2024, meaning more Australians are living with its consequences. It was the leading risk factor for males aged 45 to 84 and for females aged 45 to 54 and 85 and over.

Nutritional imbalance

The study design names six imbalances. The AIHW groups them under dietary risks, which contributed 4.8 per cent of total burden in 2024, the third leading risk factor. The largest single dietary contributors were a diet low in legumes, a diet high in sodium, a diet low in wholegrains and high fibre cereals, and a diet high in red meat.

Under-consumption of fruit and vegetables

Fruit and vegetables provide fibre, vitamins (such as vitamin C and folate), minerals and antioxidants, and are low in energy density.

• Mechanisms: antioxidants protect cells from damage; fibre and potassium support heart health and blood pressure; low energy density helps weight management; vitamins support immune function.
• Outcomes of low intake: increased incidence of cardiovascular disease, some cancers (such as bowel cancer), type 2 diabetes (through weight gain) and infections.
• Data (ABS 2022): only 44.1 per cent of adults met the fruit recommendation and 6.5 per cent the vegetable recommendation; 4.2 per cent met both. Among children aged 2 to 17, 63.9 per cent met the fruit recommendation but only 4.6 per cent met the vegetable recommendation. The proportion of adults who did not usually eat fruit daily doubled from 6.3 per cent in 2011-12 to 12.0 per cent in 2022.

Under-consumption of dairy foods

Milk, yoghurt, cheese and alternatives provide calcium, protein, phosphorus and vitamin B12.

• Mechanism: calcium is needed to build peak bone mass during childhood and adolescence and to maintain bone density with age.
• Outcomes of low intake: increased prevalence of osteoporosis and fractures later in life, especially among older women after menopause, increasing morbidity and YLD from musculoskeletal conditions. Reduced-fat dairy is recommended for most adults.

High intake of fat (particularly saturated and trans fat)

• Mechanism: saturated and trans fats raise LDL cholesterol, contributing to plaque in arteries (atherosclerosis). Fat is also energy dense (about 37 kJ per gram, more than double protein or carbohydrate), so high intake contributes to weight gain.
• Outcomes: increased mortality from coronary heart disease and stroke; increased prevalence of overweight and obesity and type 2 diabetes.

High intake of salt

• Mechanism: excess sodium causes fluid retention and raises blood pressure.
• Outcomes: increased incidence of hypertension, stroke, coronary heart disease and kidney disease. A diet high in sodium was the second largest dietary contributor to burden in 2024. Most dietary salt comes from processed foods rather than the salt shaker, which is why reformulation and food labelling matter.

High intake of sugar

• Mechanism: added sugars, especially in sugar-sweetened drinks, add energy with little nutritional value (energy-dense, nutrient-poor), contributing to weight gain; sugar also feeds the bacteria that cause tooth decay.
• Outcomes: increased prevalence of overweight, obesity and type 2 diabetes; increased dental caries.

Low intake of fibre

• Mechanism: fibre adds bulk and speeds the passage of waste through the bowel; soluble fibre slows glucose absorption and lowers cholesterol; fibre increases satiety.
• Outcomes of adequate intake (as the 2023 exam required): reduced incidence of bowel cancer, constipation and diverticular disease; reduced risk of type 2 diabetes and coronary heart disease; easier weight management. Sources include wholegrains, legumes, fruit and vegetables.

Positive framing: the effect of improving these factors

Many questions ask about prevention or adequate intake, not the harm. The 2024 report gave no marks to answers about how obesity affects health status when the question asked about preventing obesity, and the 2023 report gave none to answers about a lack of fibre when the question asked about adequate fibre. Practise both directions:

• Preventing obesity decreases the incidence of type 2 diabetes and increases life expectancy.
• Adequate vegetable intake decreases the incidence of bowel cancer and decreases mortality from cardiovascular disease.
• Adequate dairy intake decreases the prevalence of osteoporosis and reduces YLD from fractures.
• Lower salt intake decreases the incidence of stroke and reduces DALY from cardiovascular disease.

Dimensions of health and wellbeing

• Physical: body weight, blood pressure, energy, immune function, bone strength.
• Mental: self-esteem and body image; diets high in fruit and vegetables are associated with better mood.
• Social: ability to participate in sport and social activities; weight stigma can cause exclusion.
• Emotional: managing emotions without comfort eating; resilience.

Variations between groups

Overweight and nutritional imbalance help explain variations in health status: males are more likely to be overweight or obese, and males met the fruit and vegetable recommendations less often than females (2.1 compared with 6.3 per cent meeting both in 2022). Explain these with sociocultural and commercial factors (income and food affordability, marketing of energy-dense foods, time pressure, cultural food practices) and environmental factors (access to fresh food outlets, safe places for activity), not personal blame. The challenges of changing diets are analysed in promoting healthy eating.