The Meaning of BMI, How to Calculate It & How to Understand It

Most of us have heard the term BMI, but do we know what is stands for? BMI stands for body mass index and is used to calculate an estimate of body fat using weight and height. BMI is used for several reasons such as to determine if one is overweight, underweight or to assess one’s risk of underlying health conditions. BMI is an easy and inexpensive tool to utilize, but it is also important to understand that BMI is not a textbook measure of one’s health.

How to calculate BMI

For men and women over the age of 20, BMI is calculated using a simple formula. First, you will need your height, in inches, and your body weight. Once you have these two factors, you will plug the numbers into a simple formula. The formula for BMI is: weight divided by height squared, times 703.

For example, if you weigh 160 pounds and are 5 foot 6 inches, or 66 inches tall, your personal formula is this: 160 divided by 66 squared (which is 4,356) times 703 equals 25.8

You can also electronically calculate your BMI using the CDC’s Adult BMI Calculator. Once you have your BMI calculations, it is important to understand how to interpret the data.

Understanding BMI calculations

After calculating your BMI, the next step is how to interpret this information. For adult men and women over the age of 20, BMI is interpreted using a standard weight category chart. For men and women under the age of 20, a similar chart is used but instead of interpreting the results using just weight and height, other factors such as age and sexual orientation are used to determine one’s BMI. Here is a general chart used to interpret BMI calculations:

If we used the example above of the 5-foot-6-inch person weighing 160 pounds, their BMI calculation of 25.8 would place them in the “overweight” column. It is important to remember here that while BMI is an estimate and not a textbook measure of body fat, BMI is a reliable way for one to screen for weight categories that may lead to health problems.

Why calculate BMI?

A main reason BMI is calculated is to help a person maintain an appropriate weight for their body type. BMI is also calculated for several other reasons such as to determine which weight category one lies in or to help determine if one is underweight or overweight. Being in the overweight or obesity category can put one at higher risk for developing underlying health conditions such as:

• Heart disease
• High blood pressure (hypertension)
• High cholesterol
• Stroke
• Sleep apnea and breathing problems
• Type 2 diabetes
• Mental Illness such as clinical depression, anxiety and other mental disorders

For those who fall into the “underweight” category, the health risks associated in that category are:

• Malnutrition
• Osteoporosis
• Anemia
• Exhaustion

Limitations of BMI

For most people, BMI is an easy tool to use for an estimate of body fat, but it does not work for everyone. There are a few limitations BMI does not factor in:

• The calculation may overestimate the amount of bodyfat in a muscular person or underestimate the amount of body fat in an elderly person who has lost muscle.
• Since the equation only uses weight and height, it does not factor in age or sex. Women tend to have more body fat than men and an older person has more body fat than a young person.

BMI and heart health

Heart disease is the leading cause of death in both men and women. It is important young people and people of all ages are aware that whether you are overweight or underweight it can affect your heart health.

People whose BMI calculations fall into the “overweight” or “obese” category, this can put a strain on their heart. When fat builds up around the heart, the heart is compressed, making it difficult to pump blood throughout the body properly. Being in this category increases the risk of heart disease, heart attack and even heart failure.

People whose BMI calculations fall into the “underweight” category are also at risk for heart problems. This category is more at risk for cardiac abnormalities such as irregular heartbeats and heart failure. Without the body getting the proper nutrition the body is not functioning properly, and the cycle is disrupted. An improper diet can also cause the muscles around your heart to break down to use for energy which weakens the heart.

Maintaining a healthy weight can allow one to improve their overall health. Like most things, BMI does have its limitations. The benefits of upholding a healthy diet and exercising regularly exceed beyond your heart health.