The Body Mass Index (BMI) is a widely accepted method for assessing and categorizing an individual’s body weight within a healthy range. Many institutions have ratified this tool as scientifically valid, but a closer examination of its historical impact reveals how it has caused more harm than good. Over time, it has proven to be less scientifically accurate as a single indicator of health.
The American Medical Association (AMA) recently released a statement on overvaluing BMI as a measure alone for a person’s health, and published further supporting material which refocuses personal health goals for patients.
Even though we now understand how this extensively employed and acknowledged tool is overly simplistic and fundamentally flawed, we have years of conditioning which link an individual’s BMI to their health status. This connection leads to the stigmatization of fat individuals.
Dr. Hyeyoung Woo—a professor of sociology at Portland State—explained the internalization of fat stigma. “‘How [is] my body perceived socially, in a public setting?’” she said. “A lot of people have really complicated feelings and emotions, and experiences associated with that. And if your body is not something that is socially acceptable, socially desirable, there’s also another layer attached to that vulnerability.”
The concepts around BMI create harm towards fat bodies. It normalizes the language of overweight or obese in categories as indicators of an individual’s health despite—and often in opposition to—other tools which measure health. This concern for one’s health based on their BMI shrouds people’s ability to get help, sometimes creating barriers to necessary medical treatments.
“When doctors are prescribing weight loss, they’re prescribing something that fails in the long term a majority of the time,” said Debbie Kaufman, a senior instructor at the OHSU-PSU School of Public Health. “And, weight loss attempts are not benign. Especially for those who begin attempting weight loss earlier in life—it is correlated to higher risk for eating disorders, and weight cycling (repeated attempts at weight loss), [and] is associated with negative health outcomes”.
Doctors often see weight as a concern and suggest lifestyle changes or diets which often aren’t adequate. The focus on size as an indicator of health goes beyond those doctor visits, impacting fundamental ways people live their lives.
“This expands past the medical system,” Kaufman said. “We all suffer under this diet culture system because either you are living in a larger body and dealing with the consequences of the stigma, or you live in fear of your body becoming bigger.”
There’s an important distinction and clarification in science—correlation does not equal causation. “We have treated body size—or BMI—as an indicator of health, and there are correlations, for sure,” Kaufman said. “For example, more people with larger bodies have type two diabetes. But then we make the leap that the larger body causes type two. We don’t know what causes it, and stress is more highly correlated to diabetes than weight.”
This is why BMI is so dangerous as a single tool for determining health. “We’re blaming health outcomes on our body size, when more and more research is showing that it might actually be the stigma, the stress of living with that stigma, [or] the lack of appropriate access to health care that those things actually might be causing,” Kaufman said. “And be careful about the use of [the word] cause.”
Stress is often due to factors outside of one’s control. “Our stress response is very outdated,” Kaufman said. “Our body sends us a signal [that we] need fuel[…] You ignore that, then over time your body goes into a famine response, storing fat and slowing metabolism[…] Because it’s thinking, ‘This person lives in a really unstable food situation, so I have to store fat for the next famine.’”
Moreover, stress is so often a creation of oppression and a lack of resources. “We know that the impacts of oppression have so much more of an impact on your health than what you eat,” Kaufman said. “And yet, we keep focusing on what you eat. Eating healthy is good for your body, but it’s not going to have as much of an impact as having opportunities to rise out of poverty. So public health needs to change”.
These nuances around fatness add complexity to the idea that a high BMI equals low morality and self-control. In fact, it seems to stand in opposition to that bias. Nevertheless, the connection between fatness and positive values is lacking in our culture, and this leads to shame which restarts the stress cycle.
Our bodies are intricate, and the fundamental desire to cure fatness is flawed. Portraying fatness as a personal issue misrepresents it as a choice rather than recognizing that it’s often a stress response. It simplistically turns a complex condition—which is influenced by multiple factors—into a perceived personal moral failing. “This is not like a personal, individual issue,” Dr. Woo said. “And it is clearly a social issue, because otherwise we won’t be seeing social patterns.”
Kaufman will be teaching a public health course called Body Liberation for Health this upcoming winter term. Public health bridges the gap between the medical world’s jargon and everyday people. It ensures that complex health concepts—such as obesity—are understood nuancedly, steering clear of oversimplified measures such as BMI.