A new study has found that waist size is more accurate at assessing whether you are at risk for an array of health problems than body mass index (BMI).
The study conducted by the University of Iowa and published in July in the Journal of the American Medical Association Network Open, a monthly medical journal published by the American Medical Association, 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 premature death based on their waist circumference.
BMI a blunt instrument
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 ‘healthy’ weight is defined as a BMI of 18.5 – 24.9. 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 over.
BMI has been used for over 100 years to help health professionals decide whether a patient is overweight or underweight. Many healthcare practitioners rely solely on BMI to determine obesity-related health risks in their patients, 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) content.
Unseen dangers of visceral fat
This 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 in fact still fall into a high-risk group because of other risk factors such as their total body fat percentage and central obesity, which is an indicator of visceral or ‘organ’ fat.
Central obesity has been linked to an array of health problems and is measured by waist circumference. 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 vital organs such as the heart, kidneys, liver, digestive organs and pancreas. This can increase the risk of heart disease, stroke4, type 2 diabetes and cancer.
The bottom line is that you can have a healthy BMI and still have excess tummy fat, which means that you are still at risk of developing some of these diseases.
How to measure your waist:
- When taking measurements, pull the tape measure so that it sits on the surface of the skin, but does not compress the skin6
- Find the top of your hip bone and bottom of your ribs
- Breathe out normally.
- Place the tape measure between these points, and wrap it around your waist to get an accurate measurement
- In most people, your natural waist should be the narrowest part of your torso.
According to the World Health Organization and National Health and Medical Research Council recommendations, women are at risk if their waist measurement is over 80cm. Those at a very high risk include women with a waist circumference of more than 88cm.
In the study of over 156,000 post-menopausal women, those with normal weight and central obesity had a similar risk of obesity-related disease compared to women with a BMI over 30, or obese.
Regardless of your height or BMI, you should try to lose weight if your waist measurements exceed that levels that indicate your health is at risk.
If you are trying to lose weight, it can be as basic as eating less and being more active. Speak to your doctor about weight loss management options that might be best for you, particularly if you fall within the very high risk group, or consult with health and fitness professionals who can provide you with a suitable weight-loss program.
Author: Pedro van Gaalen
When he’s not writing about sport or health and fitness, Pedro is probably out training for his next marathon or ultra-marathon. He’s worked as a fitness professional and as a marketing and comms expert. He now combines his passions in his role as managing editor at Fitness magazine.