Body Mass Index

Medical News Today, 2017

Do you ever leave the doctor’s office with more questions than answers?  Or maybe you are familiar with a term or measurement the doctor used but need a refresher on what exactly it means or why it is important.  Over the next few weeks we will discuss common assessments and terms that might help you at your next visit.  A few topics I will touch on include waist circumference, cholesterol types and levels, and blood sugar.  Our first discussion will look at BMI.   

Doctors use a variety of tools to make health assessments; because of its popularity, you may be familiar with body mass index or BMI.  Developed in the mid-1800s, BMI is a simple way of assessing the general health of a person with an average fitness level.  BMI was originally developed as a tool to evaluate overall populations, rather than an individual assessment, but because of its ease of use, it has become a popular tool in an initial medical evaluation.  

Mathematically, BMI is your body mass divided by your body height squared.  Since this is generally calculated in in the metric system, those of us used to pounds and inches also need to multiply the above result by 703. BMI is helpful to doctors because it categorizes patients into four categories (in the US): Underweight = <18.5, Normal weight = 18.5-24.9, Overweight = 25-29.9, and Obese = >30 (NIH, 2005).  For example, if you weight 160 and you are 5’5” you would divide 160 (weight) by 4225 (height in inches times itself, 65x65) and then multiply that by 703 which equals 26.6.  Your BMI is 26.6 and puts you in the overweight category.  

For some, BMI is known to provide a slightly skewed assessment.  If you are an athlete or have a high muscle to fat ratio, your BMI will be higher than someone of a similar shape and size due to muscle weighing more than fat.  It is always important to remember that people come in all shapes and sizes and one assessment can only give a general idea of health. 

In general, BMI is a useful tool. Even if you are not in the normal weight range, you can use the number to compare where you are to where you should be for health purposes.  If you have questions regarding your BMI, talk to your doctor.  Before beginning any exercise program or changing your physical activity patterns, you should always consult your doctor.  

As always, if you have questions, concerns, or just want to chat, please feel free to come by the Hunt County Texas A&M AgriLife Extension, 2217 Washington Street, Greenville, Texas, 75401, call (903) 455-9885, or email Sarah.Latham@ag.tamu.edu. 

References:

Medical News Today. (2017). http://www.medicalnewstoday.com/info/obesity/what-is-bmi.php
National Institutes of Health (NIH). (2005). National Heart, Lung, and Blood Institute. Aim for a Healthy Weight.  Publication No. 05-5213.