Body mass index (BMI) and waist-to-hip ratio (WHR) are two main anthropometric measurements to screen for obesity. These two methods are used by many medical professionals worldwide.
Although BMI is more commonly used, there are many experts who think that formula has extreme flaws and should be replaced with alternatives, such as the waist-to-hip ratio. One of these skeptics is Olivia Affuso (PhD) whose research focuses on the prevention of obesity and health issues through physical activity. In her public speeches, she tells stories of people who were being denied health and medical care, because of their ‘unacceptable’ body mass index.
Today, the team at Healtypedia will dig into the BMI measurement and find out why the waist-hip ratio may be a better option to monitor your health.
What is BMI and how is it measured?
BMI, or body mass index, is defined as the body mass in kilograms divided by the square of the body height in meters. A body mass index in a range between 18.5 and 24.9 is considered healthy.
For example, a man who has a height of 180 cm (5’9) and weighs 75 kg (165 lbs) has a BMI of 23.1 kg/m2. and falls into a ‘healthy range’.
What is the waist-to-hip ratio?
Waist-to-hip ratio (WHR) is a measurement used as a health indicator, and first of all to check someone for abdominal obesity. This ratio is determined by dividing the circumference of the waist by the circumference of the hips and is typically expressed as a decimal.
For example, a woman with a waist circumference of 75 cm and hip circumference of 100 cm, would have a WHR of 0.75, which is a healthy result. But the higher the WHR number – the more fat is distributed around a person’s belly.
Six downsides of BMI
1BMI does not take muscles into account
When it comes to BMI, having a higher amount of muscle mass can throw off the accuracy of the measurement. Because muscles weigh more than fat tissue, people with higher amounts of muscle mass may have a BMI that inaccurately indicates they are overweight or obese when in fact they are not!
We previously mentioned Olivia Affuso, PhD, an advocate for BMI’s improvement. In one of her public speeches, she shared a story of her athletic friend and a former football player. He was injured during a marathon and then denied in surgeon’s appointment because his BMI was 36. He was considered overweight even though his body had more muscles in proportion to fat, and was relatively low body fat.
Other cases included people with mental health problems, such as anorexia or bulimia, denied medical treatment by the insurance companies because their BMI wasn’t in the ‘right’ range. The fact that the current BMI method doesn’t distinguish fat from muscles is the measurement’s biggest issue due to these impacts.
2BMI may not accurately reflect health dynamics in your body
This issue follows the previous one directly: body mass index cannot show you the proper dynamic of how your body changes. Whether that is a positive or negative change, in many cases, it just does not work as well as WHR.
Imagine that your height is 180 cm and your weight is 105 kg. In this case, your BMI is 32.4 and you are considered obese. After hearing this news, you decide to improve your lifestyle and run every day to feel healthier. In a few months, you scale you’re improving your lifestyle, starting to run every day and feel healthier, but after a couple of months, your bathroom scale shows 104 and you’re still considered obese with a BMI of 32.1. You would probably feel a little bit discouraged! What this does not show is that you have likely lost a few pounds of fat while gaining muscle, an unquestionable improvement.
Another example is the body mass index of elderly people, who are known to lose muscle mass and gain fat instead. If their BMI was healthy before, they would be still considered healthy, even if their body is undergoing unhealthy processes.
By measuring your waist and hip circumferences regularly you can clearly see the changes in your body composition and make some adjustments in your lifestyle to improve your health just in time.
3Unlike BMI, WHR shows the fat distribution
We’ve all heard of the ‘apple-shaped’ versus ‘pear-shaped’ debate – and sometimes even an apple can be healthy, according to certain BMI metrics! In reality, the BMI method doesn’t account for body fat distribution, unlike the waist-to-hip ratio.
Measuring both the waist and hips provides a more accurate estimate of body fat:
The higher WHR – the more abdominal fat the person has.
A lower WHR indicates greater lower-body fat.
By calculating your WHR you can easily monitor the risks of abdominal obesity and prevent it from resulting in health issues such as diabetes, cardiovascular diseases, and hypertension.
4BMI doesn’t take into account biological sex differences
When relying solely on BMI to determine if a person is healthy or not, one of the most important factors that can be overlooked is biological sex difference. This happens because the BMI method was created during a time when the differences between male and female bodies weren’t as examined.
Waist-to-hip ratio, on the contrary, distinguishes male and female bodies and provides separate cut-off points for the two genders.
5WHR is proven to have a better correlation with health issues
Waist-to-hip ratio calculation is becoming increasingly popular as a more accurate predictor of overall risk for diseases. Numerous studies have demonstrated WHR to be more strongly correlated with a chance of developing various illnesses than BMI.
One of the studies that involved more than 5,000 Taiwanese people showed that WHR is a better anthropometric index for predicting the risk of type 2 diabetes. The researchers even defined the optimal cutoff values as 0.89 for men and 0.82 for women.
Another study of 57 obese women concluded that waist-to-hip ratio is a better indicator of poor cardiac status than BMI. The WHR index showed a better connection with changes in blood pressure, total cholesterol, and HDL cholesterol, compared to the body mass index.
According to the most recent research, the waist-to-hip ratio is a stronger, more consistent predictor of all-cause mortality than BMI and FMI (Fat Mass Index). For example, each one-unit increase in WHR increased the odds of early death by almost twice as much as a one-unit increase in BMI or FMI.
6WHR is more available than BMI
Both of these methods are inexpensive, but WHR is still considered cheaper. Not everyone has a bathroom scale or access to a gym where they can weigh themselves regularly. We don’t want to underestimate the importance of knowing your weight, but in this case, the waist-to-hip ratio seems more available – all you need is just a measuring tape that many have in their houses.
Another factor is that measuring your own height by yourself may also seem like a challenge to some. But measuring your waist and hip circumferences is a pretty easy task even if you have no help around.
WHR versus BMI: Which indicator is better for monitoring your health?
Many factors suggest that the waist-to-hip ratio is a better way to measure obesity and predict health issues than BMI. Unlike other calculations, it shows the distribution of fat around certain areas and does not mix muscle mass with fat. The waist-to-hip ratio can help you to clearly see the dynamic of your body changes and you can do it even if you don’t have a bathroom scale at home.
It is clear that BMI should not be used exclusively to judge if a person is healthy and, of course, should not be a discriminating factor in receiving medical treatment. It is important to keep in mind that BMI provides information based on averages, so it is not always 100% accurate. In the end, the two calculations work better in combination with other measurements. Knowing your own body composition is key to ensuring you are receiving adequate care based on realistic and clinically sound evidence.
Want to learn more? Here is additional content from the experts
To find out more about why BMI doesn’t work the way it’s supposed to, watch this cool and short investigation done by the Vox YouTube channel.
Receive Exclusive Tips & Weekly Digest – subscribe to our newsletter