Beyond the scales: Why body composition matters

Health messaging often focuses on how much we weigh, but the number on the scales is only part of the picture, Healthy Food Guide dietitian Jess Burvill explains.

From birth and throughout life, body weight is seen as a key indicator of health. But the number on the scale doesn’t tell the whole story. Two people may weigh the same but have vastly different health outcomes depending on their body composition — the balance of fat, muscle, bone and water in their bodies. Understanding body composition provides a much clearer picture of overall health, fitness and potential lifespan than weight alone.

What’s inside?

Let’s take a closer look at the key elements of body composition:

• Subcutaneous fat is the layer of fat just beneath the skin that you can see and pinch, making up the majority of the fat that’s stored in our bodies.
• Visceral fat is the hidden belly fat stored around vital organs like the heart, liver, pancreas and kidneys.
• Muscle mass encompasses all the muscles in the body, including skeletal muscle which is important for mobility, balance and strength.
• Bone mass is the total weight of all the bones in our body.
• Water makes up roughly 60 per cent of our body and is essential for controlling body temperature, carrying nutrients and ensuring our organs function properly.

How body composition impacts your health

Chronic disease risk

Having too much body fat, especially visceral fat, is closely linked to serious health issues like heart disease, type 2 diabetes, certain cancers and liver disease. While some is necessary to protect your organs, too much visceral fat can be particularly harmful because it releases biologically active substances that can lead to inflammation and hormone imbalances.

Metabolic health

People with more muscle and less fat tend to enjoy better metabolic health. More muscle helps keep blood sugar levels stable, improve insulin sensitivity and boost metabolism, making it easier to maintain a healthy weight.

Physical function

As we age, our bodies can lose muscle and bone mass. This decline in muscle decreases our strength, which can affect our balance and movement, leaving us more susceptible to falls and fractures. According to exercise physiologist and university lecturer Amanda Burdett, it becomes even more important to add strength training into our exercise regime as we get older.

“Everyday movements we take for granted, like climbing stairs or standing up, actually require significant strength. Regular resistance exercise is crucial for maintaining the strength we need to stay mobile, active and independent in later life,” she says.

Longevity

Research consistently shows that your body composition, not just your weight, affects how long you live. People with a healthier body composition – more muscle and less fat, especially visceral fat – tend to live longer and enjoy a better overall quality of life.

How is body composition measured?

Waist circumference

Measuring your waist is a simple way to gauge abdominal fat and probably the most practical method for everyday people who aren’t athletes. A larger waistline often indicates higher levels of visceral fat, meaning as your waistline grows, your health risks do too.

Skinfold analysis

This test estimates body fat percentage by pinching and measuring fat at multiple sites on the body using handheld callipers. It’s a simple, cost-effective method, but accuracy depends on technique, and it can only measure subcutaneous fat, not visceral fat, muscle or bone mass.

Bioelectrical impedance analysis (BIA)

Used in ‘smart’ scales, BIA estimates body composition by sending a small electrical current through the body while the user stands on or holds a device. While BIA is a quick, safe and affordable way to track changes in fat and muscle mass over time, its accuracy can vary significantly due to factors like hydration levels.

Dual-energy x-ray absorptiometry (DEXA)

For a detailed look at your body composition, DEXA scans are one of the most accurate methods available. DEXA uses two low-dose x-ray beams to measure your subcutaneous and visceral fat, muscle mass and bone density. Although DEXA scans provide a lot of useful information, they are more expensive compared with other options.

Magnetic resonance imaging (MRI)

MRIs use magnetic fields and radio waves to create detailed images of body tissue. Considered the gold standard for analysing body composition, their high cost and limited availability make whole-body MRIs impractical for most people.

What is the ideal body composition?

Healthy ranges vary depending on your age and gender. For men, a good target is 10-25 per cent body fat, with a waist circumference below 94cm. For women, the ideal range is slightly higher, around 20-32 per cent, with a waist circumference below 80cm. These targets reflect the natural differences in fat distribution between genders: women typically store more fat in their thighs, hips and buttocks, while men tend to store higher levels of visceral fat around the abdomen. Although there’s no universally agreed-upon percentage for healthy muscle mass, more is typically better.