In this article, we introduce you to the basics of how to interpret Body Mass Index (BMI), what a healthy BMI is, why it’s important and how you can achieve it to lead a healthier life.
What is BMI?
Body Mass Index (BMI)is a system of classifying the body weight of adults. A person’s BMI score helps to show whether their weight is in a healthy range.
Getting an accurate BMI
To work out your BMI score, you need to know:
- your height in metres
- your weight in kilograms.
Your measurements should be as accurate as possible. Weigh yourself for a few days in a row, at the same time each day. Getting on the scales naked is the easiest way to achieve consistency.
It’s more difficult to get an accurate height measurement, especially if you’re trying to do it on your own. The easiest and best way is to ask a health professional to do it for you.
Working out your BMI score
Once you’ve got your weight and height measurements, you can calculate your BMI score.
To do this, you divide your weight in kilograms by your height in metres squared.
The calculation is: BMI = weight (in kg) / [height (in m)]2
For example, if your weight is 52 kg and your height is 1.63 m, your calculation would be: 52 ÷ (1.63 x 1.63) = a BMI of 20.
There are easy-to-use online BMI calculators such as this one on the Better Health Channel.
What does your BMI score mean?
Once you’ve worked out your BMI score, you can see which BMI category you’re in and what that means about your weight. If your BMI is:
- under 18.5 — you’re underweight
- 18.5 to 24.9 — you’re in a healthy weight range
- 25.0 to 29.9 — you’re overweight
- 30 or over — you’re living with obesity.
If you have a higher BMI (a score above 25) and are not physically active, you could be at increased risk of developing chronic health problems. These include:
- coronary heart disease (CHD)
- high blood pressure (hypertension)
- kidney disease
- type 2 diabetes
- gallbladder disease
- some types of cancer, such as colon and breast cancer
More than 60% of Australian adults are overweight or living with obesity.
Things to consider alongside your BMI score
The BMI measurement was developed almost two centuries ago during research into body sizes in Europe. This is important to keep in mind as BMI may not be the most valid measure for people today. It does, however, provide one easy and low-cost indication of an individual’s health status. BMI should be considered along with a range of other objective measures (for example, heart rate, blood pressure, waist circumference, blood glucose levels) and subjective measures (for example, how you feel during the day and your sleep quality).
BMI doesn’t take into account how much of a person’s weight is fat and how much is muscle. For this reason, a standard BMI calculation is not accurate for:
- people under 18 years
- pregnant women
- older people
- people living with eating disorders
- certain types of athletes and other people who have a lot of muscle
- certain ethnic groups, including Aboriginal and/or Torres Strait Islander peoples and people of South Asian and Asian descent.
This is why the Life! program also considers a person’s waist circumference when looking at BMI scores. Measuring waist circumference gives a good estimate of body fat, especially visceral fat (fat around your kidneys, liver, digestive organs and pancreas) and therefore your likelihood of developing weight-related diseases.
The best way of finding out whether you’re at a healthy weight is to consult a doctor or a health professional such as a dietician or exercise physiologist.
Achieving a healthy BMI
Reaching or maintaining a healthy BMI is important — it decreases your chance of developing health problems such as high blood pressure and type 2 diabetes. Even small amounts of weight loss or body recomposition (losing fat and gaining muscle), can bring about a host of health benefits.
If you want an improved BMI score, you should focus on adopting healthy lifestyle habits that help you reduce adipose tissue (bodyfat). These healthy habits should include eating nutritious food and being more active.
Eating a healthy diet that includes lots of fruit, vegetables, whole grains and a moderate amount of unsaturated fats, meat and dairy can help you maintain a healthy weight. A nutritious diet can also help you to lower your cholesterol.
Being more active
Adults should try to be physically active every day. This can include any activity in which you are moving (i.e. cleaning, shopping, playing with grandkids) or planned forms of exercise (i.e. moderate aerobic activity such as fast walking or riding a bike). Aiming to achieve at least 150 minutes per week (2.5 hours), or 30 minutes most days, will be beneficial. Simply walking more is a fantastic way of being more active, and it may lower your BMI and improve your cardiovascular health.
You should also do strength exercises that work all the major muscles (legs, hips, back, abdomen, chest, shoulders and arms) on two or more days a week. Strength training is any form of exercise involving weights or resistance, and is very effective for body recomposition. This means you can have a greater amount of muscle mass compared with fat mass. Having more muscle offers numerous benefits, including more calories being burnt throughout the day and improved glycemic control, insulin sensitivity and blood pressure.
Speak to a doctor or an exercise professional before you start strength training or significantly increase the amount of exercise you do.
How the Life! program can help you achieve a healthy BMI
If you want to achieve a healthy BMI and lower your risk of type 2 diabetes, heart disease and stroke, the Life! program will give you the support, resources and knowledge you need.
The Life! program is a free healthy lifestyle program that helps you improve your eating habits, increase your physical activity and manage stress. You can choose from a group course or our telephone health coaching service.
Our experienced health professionals will support and motivate you to make changes to your lifestyle so that you can achieve a healthier BMI.
Take this simple health test and find out if you are eligible for the Life! program today.
Ryan Marinelli, Accredited Exercise Physiologist | Life! program Facilitator and Health Coach
Kristie Cocotis, Head of Prevention and Health Promotion
Sarah Dubé, Strategy and Engagement Lead
Ria Cheripuram, Digital Communications Officer
Tegan Kohlman, Communications and Social Marketing Officer