Waist circumference is a measure of abdominal fat. Having fat around your abdomen (“apple” shape), regardless of your body size, could be a sign you have an increased risk of diseases such as heart disease and type 2 diabetes. Fat predominantly deposited around the hips and buttocks (“pear” shape) doesn’t appear to have the same risk.
Less than 94cm (men)
- 80cm (women)
For men of South Asian, Chinese or Japanese descent, the cut-off is 90cm.
When should I check it?
As often as you like — all you need is a tape measure. Measure while standing up with your stomach relaxed and after exhaling. Place the measuring tape at the midpoint between the end of the ribcage and the top of the hip bone.
Body mass index (BMI) is a measure of your weight relative to your height. It gives an approximate measure of your total body fat and indicates whether you’re overweight or obese. If you are, it’s a risk factor for other diseases and conditions such as diabetes, heart disease, hypertension, osteoarthritis and some cancers.
But BMI does have its limitations:
- It may overestimate body fat in pregnant women, athletes and others who have a muscular build.
- It may underestimate body fat in the elderly and others who have lost muscle mass.
- It can be misleading in children as body fat changes as they grow, and girls and boys also differ in their body fat as they mature.
For some ethnic groups, the cut-offs for being overweight and obese are different. They’re lower for Chinese, Indian and Malaysian people, for example, but higher for Maori and Pacific Islanders.
Less than 18.5 is underweight, 25-29.9 is overweight and 30 or higher is considered obese.
When should I check it?
Right now. Divide your weight (in kilograms) by your height (in metres) squared. A person who’s 1.65m (165cm) tall and weighs 60kg, for example, has a BMI of 60 ÷ (1.65 x 1.65) = 22, which is in the normal range.
What about my body fat percentage?
Two people with the same height and weight will have the same BMI, yet could have different amounts of body fat. At the same time, there are certain agreed levels of body fat that are considered optimal, depending on age and gender. So, it would seem body fat may be a better measure of health than BMI or waist circumference.
But there’s not a lot of data suggesting that body fat measures provide better information about health risk than other measures. It’s also much harder to get an accurate result without specialist equipment. So until more definitive research is conducted, BMI and waist circumference will work for most people.