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What is BMI and why does it matter?

February 4, 2021

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.

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Important Lap-Band® System Safety Information

The Lap-Band System is indicated for weight reduction for patients with obesity, with a Body Mass Index (BMI) of at least 40 kg/m2 or a BMI of at least 30 kg/m2 with one or more obesity-related comorbid conditions. It is indicated for use only in adult patients who have failed more conservative weight reduction alternatives, such as supervised diet, exercise and behavior modification programs. Patients who elect to have this surgery must make the commitment to accept significant changes in their eating habits for the rest of their lives.

The Lap-Band System is not recommended for non-adult patients (patients under 18 years of age), patients with conditions that may make them poor surgical candidates or increase the risk of poor results, who are unwilling or unable to comply with the required dietary restrictions, or who currently are or may be pregnant.

The Lap-Band System is a long-term implant. Explant and replacement surgery may be required. Patients who become pregnant or severely ill, or who require more extensive nutrition may require deflation of their bands. Anti-inflammatory agents, such as aspirin, should be used with caution and may contribute to an increased risk of band erosion.

Placement of the Lap-Band System is major surgery and, as with any surgery, death can occur. Possible complications include the risks associated with the medications and methods used during surgery, the risks associated with any surgical procedure, and the patient’s ability to tolerate a foreign object implanted in the body. Most common related adverse events include: Band slippage, pouch dilation, stoma obstruction, gastroesophageal reflux, esophageal dilation, cholelithiasis, incisional infection, abdominal pain, gastroenteritis, or nausea and vomiting may occur. Reoperation may be required. Rapid weight loss may result in complications that may require additional surgery. Deflation of the band may alleviate excessively rapid weight loss or esophageal dilation.

Important: For full safety information please click here or talk with your doctor.