The Lap-Band® Blog

What is BMI and Why Does it Matter?


Body Mass Index (BMI) is an easily calculable number if you know your height and weight. Despite it being so easy to calculate, there is a lot of controversy surrounding BMI. Many people don’t know what it means or understand its importance. It’s an important number to know, and it’s important to understand what it means for you.

What is BMI?

Body Mass Index measures your weight in relation to your height. It’s a good indicator of whether or not your weight is in a healthy range for your height. Knowing this number helps you and your doctor to understand if you may be at risk for developing certain health conditions or diseases.

It’s important to find a healthy weight for your body. A high BMI may put you at risk for Type 2 Diabetes, heart problems, and certain musculoskeletal problems, whereas a significantly low BMI may mean it is more likely for you to develop osteoporosis, anemia, or malnutrition. A general rule is that a BMI below 18.5 is categorized as underweight and anything above 25.0 is categorized as overweight (above 30.0 is categorized as obese). A healthy weight falls into the range of 18.5 and 24.9, which is where you want your BMI to be.


There is controversy surrounding BMI and how it is interpreted. While it’s a good measurement, it is not perfect. It does not take other factors into consideration, such as age, sex, muscle mass, and ethnicity. For instance, men tend to have less body fat than women even if they have the same BMI. Additionally, a muscular individual may have a very high BMI due to their muscle mass, not a high level of body fatness. BMI must be interpreted differently for the elderly population and teens/young adults. 

While BMI is an important number, your doctor must conduct a variety of other health assessments to determine your health and risk of certain diseases. A variety of other tests can be used to measure body fatness as well, such as skinfold thickness measurements, MRI or CT scans, and hydrodensitometry.

Bariatric Surgery

BMI is a reliable measurement used by individuals in the medical field. BMI helps determine if you are overweight enough to qualify for bariatric procedures, such as the Lap-Band® Program. The Lap-Band System is the only FDA-approved laparoscopic weight-loss device approved for people with lower BMIs (30+). Lap-Band patients with a lower BMI lose an average of 75% of their excess weight in the first year and 70% in the second year.1 In addition to taking your BMI into consideration, there are other qualifications individuals must meet in order to be eligible for the minimally invasive, safe, non-anatomy altering surgery.

1 Robert Michaelson, Diane K. Murphy, Todd M. Gross, and Scott M. Whitcup. LAP-BAND® for Lower BMI: 2-Year Results from the Multicenter Pivotal Study. Obesity (2013) 21:1148–1158.