Many people use Body Mass Index (BMI), a quick calculation of height and weight, to measure health. While easy to use and widely recognized, BMI isn’t always accurate. It also doesn’t capture important aspects of mental health, like someone’s relationship with food and body image.
Rogers Behavioral Health’s Cindy Dexter, RD, CD, registered dietitian specializing in OCD and Anxiety residential care for adults, explains how BMI falls short and why biologically appropriate weight is a better alternative.
What is BMI and how is it used to measure health?
Originally named the Quetelet Index, Adolphe Quetelet, a mathematician, sociologist, and astronomer, developed the formula to calculate the fat mass of a population based on height and weight. He was interested in finding the ideal average man using statistics. In the 1970s, American physiologist Ancel Keys reintroduced the formula and renamed it the Body Mass Index while supporting its use for estimating body fatness in a population.
BMI is a ratio using height and weight to estimate body fat. The standard BMI scale categorizes weight as underweight, normal, overweight, and obese. High body weight correlates with cardiovascular disease, diabetes, and certain cancers, while low body weight is often associated with malnutrition related to illness or eating disorders, anemia, and osteoporosis.
What are some issues with using BMI to define whether someone is “healthy”?
Since BMI was originally developed using data from a white, male population, it isn’t a reliable tool for assessing health for everyone.
BMI’s appeal was always its simplicity. Several issues highlighting its shortcomings include:
1. BMI fails to distinguish between body fat, muscle, and bone mass, which is why it will typically categorize a lean, physically fit athlete as obese. It also doesn’t account for factors including age, gender, or ethnicity. Some races have higher fat mass than Caucasians, while others are leaner in mass. The weight tables categorize many people as having an unhealthy weight, even when they are physically and mentally healthy.
2. BMI is not appropriate for a growing child. Growth charts are considered the standard for recording height and weight during healthcare visits. The results are plotted and measured in percentiles and as the child grows, their height and weight trends emerge. Using this individualized data recorded over time determines overall health more accurately than BMI table estimations.
3. A higher BMI is associated with increased costs for health and life insurance, including the loss of coverage. To lower healthcare costs, healthcare organizations, scientific researchers, and insurance providers incorporated BMI into their statistical measurements to predict a high-risk population for chronic disease. This promotes stigma by putting people whose weight history doesn’t fit within these predictions under unnecessary scrutiny.
What does it mean to have a biologically appropriate weight?
Biologically appropriate weight, or BAW, is a weight that:
- A person maintains effortlessly within a healthy relationship with food and physical activity
- Is reached in the absence of eating disorder behaviors
- Is associated with reduced preoccupation with food and body image
- Supports expected growth patterns and development milestones in children and teens
BAW isn’t influenced by a single factor, but a combination of current health status, genetics, hormones, and how the environment and a person’s lifestyle affect food choices and physical activity.
Can someone with a “normal” or “healthy” BMI be struggling with an eating disorder?
While we can’t always pinpoint the exact cause of an eating disorder, current research points toward genetic, behavioral, and social factors. When someone’s view of their body becomes distorted, it can cause unhealthy obsessions, which lead to unhealthy eating patterns. Someone can be very ill even when their weight falls within the BMI normal range, not underweight, as commonly believed.
Normal BMI ranges aren’t healthy or normal for everyone. What appears to be a healthy weight range for someone with an eating disorder may, in fact, be unhealthy if it falls below their biologically appropriate weight. It’s when they restore their weight within their BAW that they will obsess less about food, have higher energy levels, and fewer depression symptoms.
What can I do when a doctor’s comments about weight cause distress?
Being anxious during a doctor’s visit is understandable, and not feeling heard only makes it worse.
Here are three steps you can take to reduce distress when it comes to discussing weight:
1. Ask to change the subject from body weight back to the reason for the visit. Communicating needs directly can be empowering and might be all that’s needed to shift the discussion.
2. Decline the routine weigh-in if the appointment isn’t weight-related. Without a current weight, the focus stays on the reason for the visit.
3. Find a different provider who supports a weight-neutral environment if your concerns aren’t getting enough attention or are dismissed.
How do treatment teams at Rogers help people find their biologically appropriate weight?
Biological weights for children and adults are estimated differently. For children, reviewing growth charts helps clinicians see where their weight trended before the onset of disordered eating. This individualized data is often a better predictor of a healthy weight range that improves brain and body function.
For adults, BAW can be determined by collecting a weight history before the onset of the illness. The treatment team monitors eating behaviors, current body weight, anxiety levels, nutrition labs, and responsiveness to treatment as indicators of whether someone’s weight is trending toward what’s appropriate.
How can someone learn to trust their body again after focusing so long on BMI or “goal weight”?
During treatment, people receive valuable insight into how their body communicates hunger and fullness cues. Over time, they learn to be more mindful of these messages and become more confident with how they feed themselves.
Five ways someone can begin to trust their body include:
1. Become more mindful of when you feel hungry
2. Acknowledge specific food cravings without judgment
3. Break specific food rules that tell you what you should and shouldn’t eat
4. Notice the feelings of fullness after eating a meal
5. Recognize that changing focus from BMI to body signals is difficult at first
Building trust will eliminate the pitfalls of body weight screening tools that fall short in determining a healthy weight without assessing all aspects of personal health histories.
Rogers’ Registered Dietitians are a key part of our treatment teams. They help people achieve their biologically appropriate weight, so they’ll get the most out of treatment and recovery.
“Every time you listen to a food rule, you’re not allowing yourself to trust your body,” says Annie Weiss, MS, RD, CEDS, lead clinical dietitian. “Let your hunger and fullness be the path toward that trust. Listen to your hunger cues and break food rules regularly. Trust your body’s need for certain foods and the desire to have foods outside of those rules.”
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Body Mass Index (BMI) is a calculation based on height and weight used to estimate body fat and categorize weight. It’s widely used because it’s simple, but it was designed to study populations, not individual health.
BMI doesn’t account for muscle, bone, age, gender, or ethnicity. This means it can misclassify healthy people (like athletes) and overlook health concerns in others.
Biologically appropriate weight is the range your body maintains naturally when you’re eating regularly, moving in balanced ways, and not engaging in disordered behaviors. It supports both physical and mental well-being.
Yes. A person can have a BMI in the “normal” range and still experience serious eating disorder symptoms. Weight alone doesn’t reflect overall health.
Start by noticing hunger and fullness cues, letting go of strict food rules, and responding to cravings without judgment. This takes time but helps rebuild confidence in your body.
