What your waist size says about your heart health
When it comes to measuring body type and screening for overweight or obesity, tools like Body Mass Index (BMI) have often been front of mind. In fact, you may have already calculated your BMI or can do so here.
BMI is a tool used to measure the health risks linked to overweight and obesity. Typically, as BMI goes up, the risk of health problems can increase. However, some people may have a “normal” BMI (between 18.5 and 24.9 kg/m2) but still carry a high amount of body fat, particularly around the belly (abdomen).
So, although BMI can screen for overweight and obesity, it can’t measure body fat distribution (i.e., where the fat is located in your body). Body fat distribution may indicate someone’s risk of heart-related conditions, which they may be unaware of. Additionally, the link between BMI and cardiovascular risk factors can also change based on ethnicity. For example, Asian populations tend to see an increased risk of heart-related conditions at a lower BMI than Caucasian populations.
To address possible limitations to the BMI, and to help give a broader understanding of the risks associated with overweight and obesity, the Waist-to-Height Ratio can be used. This calculated ratio focuses on the relationship between waist circumference and height to identify cardiovascular risk related to overweight and obesity. By dividing your waist measurement by your height, this ratio provides insights into how fat is distributed throughout the body — particularly visceral (abdominal) fat, which may lead to serious health conditions like heart disease, diabetes, and high blood pressure.
What is ‘visceral fat’, and how does it relate to overweight and obesity?
The Waist-to-Height Ratio focuses specifically on waist circumference relative to height, to give a picture of how much fat is stored in the abdominal region.
This fat can be categorised into two groups:
- Subcutaneous fat: Typically, in adults subcutaneous fat makes up around 85% of all body fat and sits just below the skin.
- Visceral fat: This lies deeper in the body, and surrounds your internal organs such as your stomach, liver and intestines. In healthy adults, it usually makes up the other 10–15% of all the fat in your body.
Visceral fat is different from subcutaneous fat in several ways:
- Higher levels of harmful chemicals: It produces more substances that cause inflammation, which can damage your body over time.
- Fewer helpful hormones: Visceral fat also makes fewer hormones, such as leptin, that can help regulate your appetite and keep your body healthy.
High levels of visceral fat can become a problem, due to the following reasons:
- Decreased insulin sensitivity: Visceral fat reduces the body's response to insulin, increasing the risk of type 2 diabetes.
- Increased fat breakdown: Excess visceral fat can release fatty acids into the bloodstream, which may affect insulin sensitivity and increase the risk of health problems.
By measuring abdominal fat, the Waist-to-Height Ratio can offer an indication of your risk of other serious conditions linked to overweight and obesity, such as heart disease. While the thresholds for risk levels are well identified, a general rule is to keep your waist circumference to less than half of your height, to help reduce the risk of potential health problems.
The direct weight-to-height ratio is not the formal standard in New Zealand. Instead, New Zealand health agencies use Body Mass Index (BMI)—weight in kilograms divided by height in metres squared—as the primary standard. However, clinical guidelines increasingly recommend pairing BMI with waist circumference or waist-to-height ratio to accurately gauge health risks.
This information is provided for general educational purposes only and is not intended to constitute medical advice, diagnosis, or treatment. Always consult your healthcare professional for medical advice tailored to your individual circumstances.
