Disclosures: Srivastava does not report any relevant financial information.
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BMI is a good measure, but cut-off values for cardiometabolic risk can change depending on an individual’s profile.
Obesity is a dysregulation of energy balance pathways in the human body. Obese people have an abnormal body weight set point, and we can recognize and begin to address it with the simplest tool we have, BMI. You just need height and weight, and you can calculate it. However, in some populations, the standard cut-off values do not correspond exactly to the risks. Someone who is Asian and has a BMI of 23 kg/m2 or 24 kg/m2, may have a “normal” BMI, but in reality, Asian patients have a higher risk at a lower BMI. The same is true for African Americans at higher BMI threshold values.
At the same BMI, a 75-year-old person has a different risk from a 17-year-old person. As adults age, they exhibit more sarcopenic obesity, less muscle mass, visceral adiposity, and fat loss in different areas. BMI may not reflect risk for them.
Male adolescent athletes have a higher proportion of muscle mass, especially when there are growth hormones and other factors contributing to their physiology, growth and development. They may have a high BMI, but when you do the body composition analysis, they may have very high muscle mass to body fat ratio. This is also important to consider.
BMI is not 100% reliable for determining cardiometabolic risk. It is a good indicator if coupled with medical judgment and decision making.
- For more information:
- Gitanjali Srivastava, MD, FACP, FAAP, is Associate Professor of Medicine, Pediatrics, and Surgery, Director and Chief of Clinical Obesity Medicine, Director of the Obesity Medicine Fellowship Program, and Co-Director of the Vanderbilt Weight Loss Center and Vanderbilt University Medical Center .
BMI is best used as a screening tool, followed by further assessment to assess cardiometabolic risk.
BMI is a good screening tool because it’s quick, easy to calculate, and you don’t need specialized equipment. It’s something every primary care physician, specialist and patient can do. We have good standardized data showing that among large populations, BMI is strongly correlated with cardiometabolic risk. However, this correlation only concerns large populations.
When you look at individuals, there is a wide range of results for a given person’s BMI. That’s why we need to go beyond BMI when working with a patient to understand what their risk is and what treatment intensity we want to consider.
There are more accurate markers than BMI, but they require more resources and do not add enough clinical value to support their use. We can definitely improve BMI by doing an underwater body densitometry test instead. We will know exactly what a patient’s body composition is and have a much better assessment of their risk. The problem is that the test is the exact opposite of the BMI. Although it is very precise, it is incredibly expensive, it is very difficult to obtain a machine and it takes time from the supplier. For many patients, this gives us no useful additional information.
The way to improve BMI is to use it for what it is: a quick screening tool. Then, if necessary, you can take the next step and perform a more extensive test to further stratify the patient’s risk stratification. We need to treat patients individually, not according to a formula.
- For more information:
- Scott Kahan, MD, MPH, is the director of the National Center for Weight and Wellness, a faculty member at the Johns Hopkins Bloomberg School of Public Health, and a endocrine today Member of the editorial board.