Waist size is more accurate than body mass index (BMI) for assessing whether you are at risk for an array of health problems…

This is according to a study led by the University of Iowa.

The researchers found that women who are considered to be of normal weight as measured by their BMI could actually be at a high risk of many health problems or even death because of their waist size1.

What is BMI?

BMI is defined as a person’s weight in kilograms divided by the square of the person’s height in metres (kg/m2).

According to most criteria accepted around the world, a normal weight is defined as a BMI of 18.5 – 24.9.2 A patient is defined as overweight if they have a BMI between 25.0 and 29.9 and are obese if their BMI is 30.0 and over2.

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BMI has been used for over 100 years to help health professionals decide whether a patient is overweight or underweight2. Many healthcare practitioners rely solely on BMI to determine obesity-related health risks in their patients1, but some of the problems with this include that BMI does not distinguish between muscle and fat, and it does not measure overall fat or lean tissue (muscle) content2.

The study has highlighted the biggest concern with using BMI: People who think that they are healthy because their BMI falls within a “normal” range, could actually fall into a high-risk group because of other risk factors such as percentage of body fat percentage and central obesity1.

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Waist circumference measures central obesity

Central obesity has been linked to an array of health problems and is measured by waist circumference1.

Waist measurement is a simple check to tell if you are carrying excess body fat around your middle, and can be an indicator of the level of internal fat deposits around the heart, kidneys, liver, digestive organs and pancreas3. This can increase the risk of heart disease, stroke4, type 2 diabetes and cancer4.

The bottom line is that you can have a healthy BMI and still have excess tummy fat, meaning that you are still at risk of developing these diseases4

How to measure your waist?

  1. When taking measurements, pull the tape measure so that it sits on the surface of the skin, but does not compress the skin6
  2. Find the top of your hip bone and bottom of your ribs3
  3. Breathe out normally3
  4. Place the tape measure between these points, and wrap it around your waist to get an accurate measurement3
  5. In most people, your natural waist should be the narrowest part of your torso5.

When should you be concerned about your waist size?

According to the World Health Organisation and National Health and Medical Research Council recommendations, men are at risk if their waist measurement is over 94cm.

In women, the waist measurement should not be over 80cm3. Those at a very high risk include men with a waist circumference of over 102cm and women with a waist circumference of more than 88 cm3.

In the study of over 156 000 post-menopausal women, those women with normal weight and central obesity had a similar risk of obesity related disease compared to women with a BMI over 30, or obese6.

Regardless of your height or BMI, you should try to lose weight if your waist measurements are putting your health at risk. Maintaining a healthy weight is one of the best investments you can make for your health3.

If you are trying to lose weight, it can be as basic as eating less and being more active4. Speak to your doctor about weight-loss management options that might be best for you, particularly if you fall within the very high risk group4.

15 – 19 October is National Obesity Week. For more articles on obesity, click here, and to learn how to lose weight, click here.

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  1. The University of Iowa College of Public Health
  2. Medical News Today
  3. Heart Foundation
  4. NHS
  5. Very Well Fit
  6. Sun Y, Liu B, Snetselaar LG, et al. Association of Normal-Weight Central Obesity With All-Cause and Cause-Specific Mortality Among Postmenopausal Women. JAMA Network Open. 2019;2(7):e197337. doi:10.1001/jamanetworkopen.2019.7337.


While All4Women endeavours to ensure health articles are based on scientific research, health articles should not be considered as a replacement for professional medical advice. Should you have concerns related to this content, it is advised that you discuss them with your personal healthcare provider.