What is all of the fuss lately about BMI? Providers are beginning to measure this in patients and then make recommendations based upon the BMI number. So… what is so important about a BMI?

BMI or Body Mass Index is taking into account your weight distributed over your body frame – your height. BMI is often the first step in determining whether someone is obese or not.

How to measure your waist circumference:

Locate the upper hip bone and top of the right iliac crest (pelvic bone).

Place the measuring tape around your abdomen at the level of the iliac crest, keeping it parallel to the floor.

Make sure the tape is snug but not compressing your skin.

To determine your BMI, consult a chart online. You may also calculate your BMI using the following formula:

BMI = Weight (kg) divided by your Height in meters squared

Below you will find the ranges of BMI and what it means:

  • Normal Weight is a BMI of 18.5-24.9
  • Overweight is a BMI of 25-29.9
  • Obesity Class I is a BMI of 30-34.9
  • Obesity Class II is a BMI of 35-39.9
  • Obesity Class III is a BMI greater than or equal to 40

Interestingly, the BMI of 30 or greater is not some arbitrary number but when many of the medical risks associated with carrying extra weight begin to sharply increase. Having said that, the BMI alone is not the whole story. Look at some actors you may know and their BMI’s:

  • Tom Cruise at 67 inches in height and 201 lbs – BMI = 31
  • Sylvester Stallone at 69 inches in height and 228 lbs – BMI = 33
  • Arnold Schwarzenegger at 74 inches in height and 257 lbs – BMI = 32

Obviously, these people are not obese. They have quite a lot of muscle mass which does weigh more than fat. So…in addition to assessing the BMI, it is also important to determine body fat percentage and waist circumference. These two measurements along with the BMI will give a more accurate picture of whether or not someone is obese or morbidly obese.

In a clinical setting, the most accurate way to determine body composition is with impedance measurement. For men, a body fat percentage over 24 % is consistent with obesity. For women, a body fat percentage of over 30 % correlates with obesity.

A waist measurement greater than 40 for men and greater than 35 for women, correlates with increased abdominal fat, and thus increased risk for medical issues to include Diabetes type 2, Heart disease, Reflux, and even certain types of cancers.

Having said all of this, there are some people that have a normal BMI and have too much belly fat. This puts them at increased risk for these metabolic diseases as well.

So…knowing your BMI is valuable. Strive to keep this in an acceptable range. If you have a higher BMI, healthy eating and increased activity will bring about weight loss and a healthier BMI! Even if your BMI is not elevated, be cautious of carrying too much fat tissue especially in the belly area!

Kathleen Baskett, MD is the Medical Director of Weight Management at St. Vincent Healthcare. She is a graduate of the University of Maryland School of Medicine, and the author of “Moving Forward: The Weigh to a Healthier Weight.”