A Child’s BMI Does Not Determine Their Health

The BMI is a generalized metric based on the ratio of weight to squared height that’s proven to be ineffective and dangerous, yet it is still "the norm." Especially for kids, BMI (or BMI-for-age) on its own is not an accurate indicator of health. There is a general consensus among leading health organizations that BMI should not be the only factor used to determine a child’s health. However, children, just like adults, face stigma and assumptions of disease based solely on their weight.

If a child’s weight lands above the BMI-for-age cutoff for obesity, their doctor will likely inform them that they are at risk for all sorts of illnesses, and the patient will be told to, of course, “lose weight.” Many of us have heard phrases like this, and they tend to incite shame, as doctors often deliver these statements without tact or empathy. So, why is BMI the standard and why doesn’t it work? Let’s look back.

In the 1830s, BMI was created. The first thing to know about the BMI is that it was created by Belgian mathematician (not doctor) Lambert Adolphe Jacques Quetelet. When he set out to find the "l'homme moyen" or the "average man,” his belief was that if you could take thousands of measurements and compare them, you could find the “ideal weight.” Through calculating these samples, he found that weight typically increases in relation to the square height of a person, and the study became the standard BMI we use today.

There are just a couple major problems with this. In an experiment meant to be for the “average man,” Quetelet only conducted this on participants who were western European men. His experiment and its results were never meant to be applied to individuals or children, only populations. For kids, the traditional BMI is combined with a growth chart, creating a hierarchical and oversimplified illustration that is often used as the sole determinant of a child’s health and rate of physical development.

A study by Boston Medical Center Pediatrics in 2017 determined that there should be serious caveats to using BMI for children, especially those 9 years old and younger, because BMI is actually an inaccurate measure of a child’s body fat percentage. Accordingly, if a person under the age of 18 is given their BMI, that number doesn’t mean what a lot of parents – or healthcare practitioners – think it means.

Breaking it down further, BMI is a measurement determined by two physical characteristics: height and weight. The formula is simple: BMI = (weight in kilograms ÷ height in meters) squared. BMI reflects only these two physical characteristics of a person while disregarding all other considerations, and yet most people believe that someone with a “normal” BMI is healthy and someone with a high BMI (categorized as “overweight” and “obese”) is unhealthy. This supports a multitude of false narratives, but the truth is that a child’s BMI does not adequately measure their health.

In December 2021, US Surgeon General Dr. Vivek Murthy declared a youth mental health crisis, stating that "even before the pandemic, an alarming number of young people struggled with feelings of helplessness, depression, and thoughts of suicide — and rates have increased over the past decade.” National data shows that about 7-8% young people attempt suicide each year, and about 17% divulge having experienced serious suicidal ideation. Young people are also significantly at risk for eating disorders. Global reports indicate that one in five children show signs of disordered eating, leaving them more likely to think about, attempt, and die from suicide.

So why the hyperfocus on BMI and obesity?

In society, simple solutions are valued over complex analysis of complex subjects. It’s much easier to say if you’re this BMI, you’re unhealthy, instead of examining the complex and varying factors that go into a person’s health. An oversimplification of children’s health specifically has led to a hyperfocus on weight loss, including extremely concerning recommendations for bariatric surgery as young as 13 years old. One 2020 article from the Journal of the American Medical Association discusses the specific focus on weight loss in youth, stating that weight control efforts “rarely result in health improvement or sustainable weight loss and are instead associated with disordered eating and greater weight gain.”

But despite the evidence, weight stigma, which can be defined as “discriminatory acts and stigmatizing beliefs directed toward those perceived to carry excess weight,” perpetuates the use of BMI.

The thing is, BMI isn’t just a terribly outdated and inaccurate tool – it’s actually killing people. It negatively impacts those in larger bodies, in particular, and, as a direct result, the majority of doctor visits for patients in larger bodies are recorded as lasting a shorter length of time than visits from folks in thinner bodies for the same ailment. When it comes to determining a child’s health or diagnosis, many healthcare practitioners ignore and gloss over higher weight children’s ailments, pointing to their physical appearance and BMI rather than doing a thorough physical exam or mental wellness check.

A child is 242 times more likely to have an eating disorder than they are to have type 2 diabetes.

Yet the vast majority of our public health education is spent warning parents (and kids) about “childhood obesity”.

Why? Fatphobia (not health).

— Alissa Rumsey, MS, RD, CDN, CSCS (she/her) (@alissarumseyRD) February 15, 2021

I know a lot of parents are worried about their kid(s)' weight and risk for type 2 diabetes – so were mine. I’d like to challenge that concern with some hard truths. The reality is that a child is 242 times more likely to have an eating disorder than they are to have type 2 diabetes, according to research from the 2014 book Body Respect by Lindo Bacon and Lucy Aphramor.

Registered dietician Alissa Rumsey emphasizes, “If you took a sample of 100,000 children, only 12 would have type 2 diabetes, whereas 2,900 would meet the criteria for an eating disorder.” Learning more about eating disorders and the warning signs is critical as the focus on BMI and weight loss for children intensifies.

As an adult, I go to the doctor’s office hesitantly. Every time I have ever walked into an exam room, from age 10 to present day, I have been told to go on a diet. I’ll add here cheekily that despite being in an “exam” room, I am not always examined, and I am almost never asked about my eating habits, receiving a disbelieving glance at my body while being asked, “Do you exercise?”

I am a fat adult, and I am OK with that. I am a leader in my field, beloved by friends and family and respected by colleagues and peers. Simply being a fat kid did not impact my overall health. Being a fat kid who experienced repeated harm and stigma at the doctor’s office because of my BMI did impact my health.
Any time a single number defines a whole human being (and, yes, children are whole human beings), there is a huge risk that the human will be overlooked. Think about your kid, your friends, your siblings, yourself. Think about what life could have been like if you weren’t judged as a kid based on your exterior. Now think about how much worse it could have been if you were told by your doctor you’re not enough. For my fellow fat kids out there, think about how that impacted your life.

And one last time for the people in the back: there is no scientific evidence that the BMI should be used as the main indicator of an individual’s health. It’s not logical, ethical, or precise… but one thing’s for certain: It is bullsh*t – especially for kids.

1. Individuals can be healthy or unhealthy at any size, a principle commonly referred to as Health at Every Size (HAES). For many decades, the definition of physical health has been the most common definition of health period, but the real meaning of “health” is much more complex.
2. Health is determined by many factors. The Centers for Disease Control says that health is determined by a number of factors, including genetics, behavior, environmental and physical influences, medical care, and social factors. BMI should not be considered the sole determinant of health but should instead be only one deprioritized consideration alongside mental health, emotional and spiritual well-being, financial security, environmental safety, physical and mental ability, behavioral habits, cultural influences, and more.
3. Eating disorders are widely prevalent. At least one in ten people in the U.S. will be diagnosed with an eating disorder in their lifetime, and 95% of first-time eating disorder cases begin by age 25.
4. Children are more at risk for suicide. Engage in hard conversations, and offer resources and support.

• How to help prevent suicide in a teen or child – NPR
• Teens and suicide: What parents should know
• Get immediate crisis support – Crisis Text Line

5. Be an advocate for your child. Know the right questions to ask at the doctor's office.

• Why You Should Be Asking Your Pediatrician Not to Talk to Your Kids About Their Weight
• Tips for Talking to Your Doctor About Their Weight Stigma
• 3 Red Flags To Help You Spot Medical Fatphobia and Weight Bias
• PSA: You Probably Don't Need to Be Weighed at the Doctor's Office