The body mass index, or BMI, predates the bathroom scale by more than half a century. But it has not changed with the times. The BMI was created in the 1830s before calculators and computers existed. It was a simple system to measure body fat based on a person's height and weight. However, in recent decades, many medical professionals have acknowledged the BMI's flawed history.
Recently, the American Medical Association's (AMA) voted to adopt a new policy that encourages doctors to de-emphasize their reliance on BMI when assessing individual patients' weight and health.
"The numbers have historically excluded patients with different ethnic and racial backgrounds since it was created to measure the 'normal' weight for a White population," says Juliana Simonetti, MD, co-director of the Comprehensive Weight Management Program at 麻豆学生精品版. "This is a great step forward in identifying and helping health care providers to effectively treat patients with obesity in a more targeted and individualized way.鈥
Flaws in Measuring BMI
Research has demonstrated that BMI does not appropriately capture the health risks associated with obesity in diverse ethnic populations.
鈥淚ndividuals from certain backgrounds, such as Asian, African, and Hispanic populations, may have a higher percentage of body fat or different fat distribution patterns at lower BMI values compared to individuals of European descent,鈥 Simonetti says. 鈥淭his means that these individuals may have increased risks of metabolic disorders, cardiovascular diseases, and other obesity-related health conditions at a lower BMI."
A well-recognized flaw of the BMI is its inability to focus on gender and age. According to Simonetti, "A higher BMI may underestimate muscle mass in a younger athlete and overestimate muscle in an elderly person who may have less muscle and more fat mass.鈥 This is something she often worries and talks about with many of her older patients that are working on weight loss.
Simonetti also recognizes new concerns that arise as the science of weight control evolves. "In particular, new medications such as Semaglutide and tirzepatide, can lead to more substantial weight loss, which is associated with loss of muscle mass,鈥 Simonetti says. 鈥淭hat, in turn, can contribute to the risk of sarcopenia, muscle weakness, and falls which are especially concerning for the elderly."
Measuring overall weight and health
While BMI can still be used as a screening tool, Simonetti says it is important to understand its limitations and use additional measures and tools such as body composition to evaluate patients for obesity-related conditions and complications.
Some other tools to access body weight and overall health include:
- Waist circumference
- Glucose levels
- Cholesterol measurements
- Liver function
- Blood pressure
- Measuring bone vs. muscle vs. body water (fluid)
Even as the BMI has virtually stood still in time, other tests and measurements designed to assess the impacts of a person's weight on their overall health are quickly being developed and put into practice. The genetics of weight gain and loss is one important example of a relatively new science that can give patients a better understanding of why their BMI indicates they have obesity.
"We now know that obesity is a highly inheritable disease, with some studies suggesting that the heritability of obesity is around 60-70%,鈥 Simonetti says. 鈥淭his means the way our bodies accumulate weight and store fat is passed down from generation to generation. We know that there are genetic mutations that further contribute to weight gain."