BMI stands for Body Mass Index, and it is one of the most-used metrics in health. When asking, “what is my BMI?” what you are actually wanting to know is how does your weight correlate to your height and if this ratio is healthy. This metric is used by health professionals and personal trainers all around the world to help decide if a person is underweight, a healthy weight, overweight, or obese. So, how can we calculate this ratio and why is BMI important?
To measure your BMI, you divide your weight in kilograms by your height in meters squared, for example, X (kg)/X (m2) = X BMI. Or, if imperial is your style, you can use this formula:
BMI = weight (lb.) / [height (in) x height (in)] x 703
Knowing your BMI, you will be able to say which category you fit into and its potential impact on your overall health.
- Underweight: BMI less than 18.5
- Healthy weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25 and 29.9
- Obese: BMI of 30+
What’s the history of BMI?
BMI wasn’t always intended as a measurement of health. In the 1830s, when it was developed by Belgian academic Lambert Adolphe Jacques Quetelet, whose primary areas of astronomy, math, sociology, and statistics, it was intended as a measurement for sociological, statistical purposes.
It was only over 100 years later that BMI began to be used in relation to a healthy weight. But even then, it wasn’t a medical tool. Instead, in the early 1940s, it was employed by life insurance companies for insurance purposes.
Soon physicians began to take notice. Though many had searched for an ideal weight-height measurement to define a “healthy” weight, it was only in the 1940s that BMI was first used in relation to medicine. William H. Sheldon made the connection in his book, The Varieties of Human Physique. However, even at the time, he noted that such a measurement was not infallible.
Still, it was another 30 years (1972) when it was first adapted as a measurement in medical practice in the form of a BMI chart due to its simple formula and convenience.
Why is BMI helpful?
It might not be a 100% effective way of measuring how healthy or over/underweight a person is. However, BMI is an efficient tool to get a general overview of whether a person is at risk of developing any significant health conditions due to their weight.
A high BMI can be a risk factor in various conditions, such as:
- Heart problems
- Muscular-skeletal disorders
In addition, it helps assess trends in populations. According to the World Health Organization (WHO), obesity has grown 3 times since 1975 and affects 39% of adults and 39 million children under the age of 5 years old.
What are the disadvantages of BMI?
It’s clear that BMI is an important tool in the measurement of health. Still, we can’t consider it to be completely accurate. BMI has some significant disadvantages too.
- BMI doesn’t tell about other health conditions. It might be an indicator of risk for certain diseases. However, BMI is not an extensive measurement. For example, it can’t indicate the level of cholesterol in the blood, blood pressure, or other factors that may impact a person’s health, aside from their weight.
- BMI doesn’t take into account muscle mass. Muscle weighs more than fat—it’s a fact. That’s why, when measuring BMI, it’s important to consider if your muscle mass could be a factor. Note, in this case, large muscle mass usually applies to pro athletes.
- BMI doesn’t consider fat composition. Studies indicate that fat composition and where it is located on the body is important. For example, fat storage around the stomach area may be riskier than that on the legs.
Are there any alternatives to BMI?
As we know, BMI isn’t perfect. That’s why when it comes to your weight, there are some other measures that may prove extra helpful in getting the health information you need. These are:
Waist Circumference Measurement.
This metric focuses on the amount of abdominal fat a person carries. As we know, belly fat is a critical factor in many health conditions. What to watch out for? A waist size of more than 35 inches or more for women and 40 inches plus for men.
You may have heard of this one about renaissance painters, but there’s nothing artistic about the waist-to-hip ratio. Again, this focuses on looking at fat distribution and its relation to health issues. For a normal weight, the waist to hip ratio should be less than 0.90 for men and less than 0.80 for women, while anything higher is divided into overweight and obesity.
Body Adiposity Index.
Like BMI, the BAI uses your height, but unlike BMI, it does not use your overall mass as a factor. Instead, it works by calculating based on hip circumference and height to give an overall figure. It works a little something like this:
BAI = (hip circumference/(height)^1.5) – 18.
How to measure your waist circumference, and what’s it got to do with BMI?
BMI is just one way of measuring the body’s weight relationship. However, by adding in waist circumference and BAI measurements, you can get a more accurate overview of how much of a problem your weight may or may not be by detecting what is known as visceral fat. This is largely unaffected by muscle mass, unlike BMI.
So, how can you measure your weight circumference? And where is your waist anyway? Grab your tape measure and follow these steps.
- Locate your waist. Look for your hip bone and wrap the measuring tape around your body. Next, move it up, so it’s on a level with your belly button.
- Try not to pull the tape too tight. Hold it gently and steadily around your waist.
- Check those numbers. You should see a number in centimeters or inches displayed on the tape. Note this number down.
What does waist measurement mean?
If your waist measurement is larger than 40 inches (101.6 cm) for a man and more than 35 inches (88.9) for a woman, you may be carrying a lot of visceral fat, which can be a health risk.
How much attention should I pay to my BMI?—BMI takeaway
BMI is a ratio. Nothing more, nothing less. While it is a helpful indicator in telling which category you may fall into health-wise and if there are any risks associated, it is not the be-all and end-all.
Instead, take BMI for what it is, a metric that tells you whether you need to follow up on something. If you’re finding your BMI is higher than expected that’s a good indicator that you need to check in with your doctor.