By The Numbers: Calculating and Interpreting BMI (Body Mass Index) 

A simple, effective, and commonly used screening method for weight status, Body Mass Index (BMI) is  defined as the body mass divided by the square of the body height, expressed in units of kg/m², resulting from mass in kilogrammes and height in metres (m). (Wikipedia)

Body fat calculator
Body fat calculator

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Meaning of BMI Ranges

  • Less than 18.5: underweight
  • 18.5 to <25: normal weight
  • 25.0 to <30: overweight
  • 30.0 or higher: obese

Obesity is frequently subdivided into categories:

  • Class 1: BMI of 30 to < 35
  • Class 2: BMI of 35 to < 40
  • Class 3: BMI of 40 or higher, sometimes categorised as “severe” obesity.

There are exceptions and variations for certain ethnic backgrounds, age, and other factors where the healthy weight BMI range is generally:

  • lower for people of Asian background
  • higher for people of Polynesian background
  • higher for older people
  • higher for elite athletes with higher levels of lean body tissue
  • higher for pregnant women.

Because the BMI method doesn’t take fat or muscle into account,  it’s helpful to measure the waist as well.   

Calculate body fat percentage
Calculate body fat percentage

How BMI Is Used

BMI can be used to screen for possible health risk factors, but it is not a diagnostic tool.  To determine if one’s BMI could pose a potental risk,  further assessments such as skinfold thickness measurements, evaluation of diet, examining physical activity, and reviewing family history can be performed by a healthcare provider. 

BMI Trends for Adults

Adult BMI scores greater than 30, which is considered obese status, have greatly increased since the 70s. This trend has levelled off recently for most groups except for adult women over the age of 60 for which rates continue to grow.

Measuring body fat percentage
Measuring body fat percentage

How BMI is Calculated

BMI calculation is based on the following formulae:

Weight (kg) divided by [height (m)]C W (kg)/H (m2)=BMI

Because height is normally measured in centimetres, obtaining height in metres is done by dividing height in centimetres by 100.

Example: Weight = 68 kg, Height = 165 cm (1.65 m)

68 ÷ (1.65)2 = 24.98

Reduce body fat and increase muscle mass to prevent cardiovascular disease, reduce blood pressure
Reduce body fat and increase muscle mass to prevent cardiovascular disease, reduce blood pressure

Australian Adult Obesity Stats in 2022-2023

Statistics show that the obesity rates in Australia have consistently increased over the past few years and are projected to continue increasing even further. IBISWorld states that the obesity percentage in Australia will hit 73.4% in a few years. 

  • Australia has had high obesity rates for several decades, with reported obesity levels in Australia rising from 29.5% in the 1970s to 32.6% in 2004-2005.
  • 66.6% of Australians in 2022 were overweight or obese.
  • Men had higher overweight rates than women in 2022.
  • The obesity rate was the same in both genders in 2022.
  • 42.2% of men aged 65 to 74 years old were obese.
  • 72.2% of adults in Australia’s more remote regions are considered obese. 
BMI method
BMI method

The rate of obesity in Australia not only affects  the lives of everyday citizens, it also affects the government.

  • Obesity-related medical treatments account for 8.6% of the nation’s health expenditures, lowering the labour market output by 371,000 full-time workers last year.
  • 36% of Australian adults (9,266,400) are overweight.
  • 31% of Australian adults (7,979,400) are obese.  
  • There has been a 10% rise in obesity rates over the past 25 years.
  • Obesity rates in Australia are projected to increase by 2% in 2023.
  • 9% of Australian adults suffer from life-threatening obesity disorders.
  • More than 1 million Australians suffer from  type 2 diabetes due to obesity.
  • 16,700 deaths in 2022 were linked to obesity and type 2 diabetes.
  • Australians account for 4% of all obese adults worldwide.
  • 140 premature deaths are caused by obesity in Australia every day.
  • Australian males have the second-highest obesity rates in the world.
  • Australia is ranked 5th among OECDs (Organisations for Economic Cooperation and Development) in obesity rates.
  • Obesity affects  1 in every 4 children in Australia.

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Obesity-Related Industries

Obesity-related industries have also been scaling up over the past few years with statistics showing considerable growth in the gym and weight loss service fields. Private hospitals and rehabs providing obesity-related services have also increased in numbers.

Reducing body fat prevents high blood pressure
Reducing body fat prevents high blood pressure

Obesity Rates Among Men and Women

Obesity rates are distributed differently among men and women.

The proportion of men and women living with overweight or obesity generally increases with age. 

  • The proportion increases from 52% for men aged 18–24 to 83% for men aged 45–54, levels out until age 65–74, and then decreases to 65% after the  age of 85.
  • The proportion increases from 40% for women aged 18–24, 73% for women aged 65–74, and then decreases to 61% after the age of 85.

Obesity in Different Age Groups 

  • Among Australians, 18% of men and 14% of women aged 18–24 years are obese, compared with 42% of men and 39% of women from age 65 to 74.
  • Among Indigenous Australian women, the proportion increases from 60% at age 18–24 to 73% at age 25–34, and peaks at 83% at 45–54.

Overweight and Obesity Rates By Demographics and Socioeconomic Status

The number of Australians aged 18 and over who are obese varies by socioeconomic levels. 

  • A greater proportion  (72%) of Australians living  in the lowest socioeconomic areas are overweight or obese, compared with those in the highest socioeconomic areas (62%).
  • A greater proportion of men (77%)  in the lowest socioeconomic areas are overweight or obese compared with those in the highest socioeconomic areas (73%).
  • A greater proportion of women (66%)  in the lowest socioeconomic areas are overweight or obese, compared with those in the highest socioeconomic areas (50%).

Obesity and Education

There is also a correlation  between obesity and income or educational levels. 

  • Men and women with college degrees had lower  prevalence of obesity rates than those with less education.
  • Among men, obesity prevalence is lower in the lowest and highest income groups compared with those with middle-income status.

How Australia Compares Internationally 

Overweight and obesity rates differ among citizens of  21 countries in the Organisation for European Co-operation and Development (OECD 2022).  

  • Australia ranks 9th out of 21 countries for the proportion of people  over the age of 15 who are overweight or obese.
  • Australia had the 4th highest proportion of obesity among men (32%), behind New Zealand (33%), Hungary (36%) and the US (44%). 
  •  Australia women ranked 9th out of 21 (29%) – higher than the OECD average of 26% for women.

Health Impacts of Overweight and Obesity Status

Disease burden is an assesment of the number of years of healthy life lost from living in ill health or dying prematurely from diseases or injuries. A portion of this burden is due to modifiable risk factors.

The 2nd leading risk factor after tobacco use contributing to ill health and premature death, obesity is responsible for 8.4% of the total disease burden in Australia. Overweight and obesity rates are linked to 30 diseases including 17 types of cancers, cardiovascular diseases, musculoskeletal conditions, type 2 diabetes, dementia, asthma, and chronic kidney disease.

In 2018, obesity was responsible for:

  • 55% of type 2 diabetes cases
  • 51% of hypertensive heart disease cases
  • 49% of uterine cancer cases
  • 43% of gout cases
  • 42% of chronic kidney disease cases

Obesity contributed to 16,400 deaths (10% of all deaths) in Australia in 2019. 

Other Ways to Assess Excess Body Fat

In addition to the BMI method, there are other ways to assess body fat including the skinfold method, waist size, and waist-to-hip circumference.

Skinfold Method

Another way to estimate body fat, the skinfold method uses skinfold calipers to take skinfold measurements. This data can be helpful in determining health risks such as high blood pressure, heart disease, and other health concerns.

Measuring abdominal fat
Measuring abdominal fat

Waist Circumference

Waist circumference can help predict the risk of some chronic medical conditions.

A higher waist circumference can indicate internal fat deposits that can coat the heart, kidneys, liver, and pancreas, increasing the risk of chronic medical conditions like type 2 diabetes, heart disease, and cancer.

Men and postmenopausal women are more likely to develop excess fat in the waist area.

Among men, a waist circumference of 94 cm or more is related to an increased risk for chronic disease. Among men, a waist size of 102 cm poses a greatly increased risk. Among women, a waist circumference of 8o cm or more poses an increased risk, while a waist size of 88 cm or more poses a greatly increased risk.  Generally, the larger the waist, the higher the risk of developing chronic conditions exists.

Body fat percentages
Body fat percentages

How to measure your waist:

  • Take off bulky clothing
  • Stand with feet shoulder-width apart
  • Wrap a tape measure around the belly  in line with the belly button, and loose enough to fit one finger inside the tape.

Health experts commonly use waist measurement in conjunction with BMI to screen patients for possible weight-related health problems. While a helpful tool, waist size is just one indicator that may point to certain health conditions, and it is not used to singularly diagnose any condition or disease.

While health experts and physicians may use this method, anyone can  measure their own waist circumference at home.

Waist Circumference

Determining waist measurements can help predict certain  health conditions. While waist size alone cannot indicate that one has a medical condition or that one will develop one in the future, it can help a healthcare provider to determine where fat is located on the body and if that body fat may cause health problems like heart disease or type 2 diabetes in the future. 

Recent reports show that 60% of men and 66% of women aged 18 and over have a waist size that poses an increased or substantially increased risk of health problems.

Waist-To-Hip Ratio

Waist-to-hip ratio (WTH) is a fast and easy way to assess fat distribution which can help determine a person’s overall risk for developing certain health conditions.

The WHR measurement involves using a tape measure to cheque the size of the waist and hips. WHR is found by dividing circumference of the waist by the circumference of the hips.

Body circumference measurements
Body circumference measurements

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How to Measure WHR

Take waist tape measurements: Wrap a tape measure around the narrowest part of the stomach, near or just above the belly button.  

Take hip measurement by standing with feet directly beneath the hips and wrapping the measuring tape around the widest part of the hips and buttocks.  

To calculate WHR, divide waist size by hip size.

The World Health Organization has established guidelines when assessing waist circumference and waist-hip ratio. A healthy WHR is 0.9 or less in men and 0.85 or less for women.

Calculating body fat percentage
Calculating body fat percentage

Non-Surgical Solutions for Fat Reduction

If you’re like so many Australians who have tried to lower their BMI and waist size with diet and exercise and have become frustrated with slow or no results, you’re not alone. The good news is there s now a way to reduce fat and contour your waist without straying yourself, spending hours in the gym, or resorting to surgery.

What is truSculpt® iD?

TruSculpt® iD is a noninvasive treatment that uses radiofrequency energy to eliminate fat cells and reduce waist circumference by effectively destroying unsightly body fat without harming the skin.

Losing weight for good body fat percentage

Where Can I Get the truSculpt® iD  Procedure?

At Specialist Skin Solutions, a cosmetic clinic specialising in non-surgical, anti-ageing aesthetic procedures, including the latest laser techniques and dermal therapies, we proudly offer truSculpt® iD, the latest in state-of-the-art body fat melting devices that slims, trims, and blasts away that stubborn fat without needles or knives. 

If you’re struggling with excess fat on your hips, butt, or waist,  you’re not alone. Thanks to truSculpt® iD, a slimmer, sexier look can be yours in just a few minutes. We invite you to give us a call to set up a consultation.  Once we have an idea of the problem and your goals, we’ll come up with an appropriate treatment plan that works for you. 

If you have specific questions, call us at 02-4934-1700.  

*Disclaimer: The number of  treatments required  to achieve maximum results may vary. Always seek medical advice and clearance before opting for any procedure, especially while breastfeeding. This article is meant strictly for informational purposes only. truSculpt® iD results vary. There are risks with any procedure. Follow your provider’s directions to the letter to stay safe and to ensure you’ll have the best results.


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