EAT FOR HEALTH Australian Dietary Guidelines

ACHIEVE AND MAINTAIN A HEAlTHY WEIGHT

13

Guideline 1

How is healthy weight assessed?

The most common approach is the use of the body mass index (BMI) calculated as weight (in kilograms)

divided by height (in metres)^ squared (kg/m^2 ).

BMI is a measure of body size that is widely used as an index of relative risk of mortality and morbidity

at the population level, with risk lowest in the healthy weight range.100,104

BMI categories for adults are as follows:104,117

•   < 18.5 kg/m^2 – underweight

•   18.5 to 24.9 kg/m^2 – healthy weight

•   25.0 to 29.9 kg/m^2 – overweight

•   ≥ 30.0 kg/m^2 – obese.

However, this classification may not be suitable for all population groups:118 , 119

•   some groups may have equivalent levels of risk at a lower BMI (e.g. people of Asian origin) or higher

BMI (e.g. people of Polynesian origin including Torres Strait Islanders and Mãori)^120

•   while specific BMI ranges have not been developed, Aboriginal people have a relatively high limb to

trunk ratio and may have equivalent levels of risk at a lower BMI

•   a higher BMI range may be desirable for people aged over 70 years.

Waist circumference is also used as a proxy for chronic disease risk in adults:12,121

•   risk is increased at ≥80 cm and high at ≥88 cm for women and increased at ≥94 cm and high at

≥102 cm for men

•   as with BMI, thresholds for other ethnic groups may differ from those for people of European descent.

For children and adolescents, continuing growth means that it is not possible to have a single set of

numerical values for BMI cut-offs that apply to all ages and both sexes. Weight appropriateness is

commonly assessed using age-related cut-off values122,123 or Z-scores (or standard deviation scores).^124

For more information, see Appendix H.

1.1.2 Health effects associated with weight status

Adults

Overweight and obesity

Overweight and obesity are associated with increased risk of type 2 diabetes, cardiovascular disease, hypertension,
metabolic syndrome, some cancers, musculoskeletal conditions, respiratory conditions, sleep apnoea, gall bladder
disease, hernia, reproductive disorders, urinary incontinence, fatty liver disease, and depression and other mental
health disorders.88,89,98,125 About 70% of people who are obese have at least one established comorbidity, resulting in
medical costs that are about 30% greater than those of their healthy weight peers.^107

Compared to having a BMI of 18.5–25 kg/m^2 , having a BMI of 30–35 kg/m^2 reduces life expectancy by 2–4 years,
and having a BMI of 40–45 kg/m^2 reduces it by 8–10 years.^126 The relative increase in mortality rate attributable to
obesity tends to decline with age.^127 Mortality and morbidity are also associated with the amount of weight gained
in adult life.89,98,101

Many obesity-related conditions are preventable, and several are at least partially reversible through weight loss
achieved by adopting a nutritious dietary pattern and active lifestyle.89,98,101