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Body Mass Index Fails to Accurately Measure Body Fat

CardioSmart News

Body mass index, often referred to as BMI, is a measure of body fat based on height and weight. Using BMI calculations, adults fall into one of many weight categories ranging from underweight to obese. And these categories can have serious implications for health, as obese patients face significantly higher risk of heart disease and other chronic disease. But just how accurate are BMI results?

In their most recent statement published in the American Heart Association journal Circulation, experts outline the pros and cons of using BMI as a tool for assessing health. Authors also highlight the limitations of using BMI calculations on minorities, as they already face higher risk of heart disease than other populations.

The good news is that BMI is a fast and simple way to determine whether a person is at a healthy weight. In under a minute, doctors can determine whether a patient is underweight, normal, overweight or obese. Based on results, doctors may also recommend weight loss through exercise and a healthy diet. BMI is also extremely cost-efficient, as calculations only take into account gender, height and weight.

But as experts explain, BMI may be too simple. Since muscle weighs more than fat, BMI isn’t accurate in patients with extreme amounts of muscle. And this can cause unnecessary concern or a faulty sense of security for many adults.

For example, a fit person with dense muscle could be categorized as overweight based on BMI. Overweight is typically associated with greater risk of heart disease, but in this case the adult is likely fit and healthy. Similarly, a patient with hardly any muscle may think they’re healthy because have a “normal” BMI. However, the fact that this person doesn’t exercise and has a high level of fat is not favorable when it comes to heart health.

That’s why authors highlight the importance of using waist circumference to assess weight. Carrying excess fat around the stomach has been shown to have a negative impact on heart health. So measuring abdominal fat may be more meaningful than calculating body mass index, alone.

Taking into account the type of body fat may also help predict a patient’s risk for heart disease. There are two important types of belly fat – subcutaneous and visceral. Subcutaneous fat is the fat that lies directly under the skin, while visceral fat lies deep within the abdomen surrounding the body’s organs. Research suggests that deep belly fat is more harmful than superficial fat, linking visceral fat to serious health problems like heart disease and diabetes. Testing the type of body fat a patient may have can help further assess their weight and overall health.

Finally, experts encourage providers to exercise caution when using tests to estimate cardiovascular risk in minorities. Regardless of weight, minorities already face greater risk of heart disease than whites. Obesity rates and cardiovascular risk also vary by race and ethnicity. So as authors suggest, it’s important to take as many factors into account as possible when assessing body fat and its impact on overall health. There are many factors that impact cardiovascular risk, such as age, race, weight and cholesterol, and addressing any risk factors can go a long way in improving cardiovascular health.

Learn about CardioSmart's editorial process Information provided for educational purposes only. Please talk to your health care professional about your specific needs.