the HAES® files: Body Mass Index Is Not a Good Measure of Your Health

by Health At Every Size® Blog

by A. Janet Tomiyama, Ph.D. and Jeffrey M. Hunger, M.A.

Note: This piece, with slight modifications, originally appeared in Zócalo Public Square.

You’ve just returned from your morning run and you’re rustling through your snail mail when you receive some shocking news—an official memo from your employer informing you that your health insurance premium is increasing by 30 percent. You’ve been deemed a health risk, and you are being charged accordingly.

Yet you’re the picture of health: A run is part of your daily routine, you passed your last physical with flying colors, and kale is your favorite food. This must be some sort of mistake. But you read the fine print to discover that your employer has decided that the most accurate measure of your health is your Body Mass Index, or BMI, which is derived by a formula that compares your weight to your height.

Even though you’re a paragon of health, at 5 foot 2 inches and 164 pounds, your BMI places you within a range considered “obese.” So your insurance company and your employer have determined that you are no longer among the “healthy.”

This may sound Orwellian, but the federal government is working to make it common. Recently proposed rules by the U.S. Equal Employment Opportunity Commission (EEOC) would set clear guidelines for employers to use metrics like BMI to charge higher-BMI employees more for their health insurance. The apparent goal of these rules is to get higher-BMI employees to reduce their weight; a standpoint based on the assumption that such individuals must uniformly face poor health. Our research, however, suggests that this assumption is flawed and these rules will not accomplish this goal. In fact, the proposed rules could yield the opposite results.

BMI is a problematic metric. It was invented more than 200 years ago by a Belgian mathematician named Quetelet, who based it on what he called the “average” human: a white male in Europe in the early 1800s. BMI also gets human biology wrong—it fails to distinguish between bone, muscle, or fat. You’ve probably heard about athletes, including the starting lineup of the Super bowl champion Denver Broncos, being “obese” by BMI standards, even though they’re very obviously in great shape. National Public Radio called the BMI formula “mathematical snake oil”!

As psychological scientists who study health, we were well-versed in the pitfalls of BMI. We knew we had to push back and illustrate the fallacy of this thinking in such a way that policymakers would understand just how many healthy people would be adversely affected.

In a stroke of good fortune rarely seen outside the movies, we found the perfect dataset. The National Health and Nutrition Examination Survey (NHANES) is a nationally representative sample of Americans surveyed every two years about their health and BMI. NHANES allowed us to look at established health markers to see who was healthy, and then see how many of those healthy folks actually fell in the higher-BMI categories employers deem “unhealthy.”

Our next challenge was to come up with an ironclad definition of “healthy.” For our analysis to have credibility, we had to have a definition that would be difficult to attack on scientific grounds. We dove into the research literature to look for different definitions and found quite a few, so we chose the definition that set the highest bar for health and used six different metrics including blood pressure, blood sugar, and cholesterol. These index the health of a person’s heart and blood vessels, risk for diabetes, and inflammation.

After crunching the numbers, the results were stunning. BMI did not map onto the real markers of health. Some 34.4 million of the 70 million-plus Americans categorized as “overweight” by BMI were perfectly healthy. That’s 47 percent! The chances of BMI being a good predictor were not much better than flipping a coin. And 29 percent of Americans rated “obese” under BMI were healthy as well. Add those numbers together—and it means that more than 54 million healthy Americans would be unfairly penalized under the EEOC rules.

Our analysis uncovered another pitfall of BMI: 21 million individuals in the “normal” BMI range—those who would be considered perfectly healthy by employers and insurance companies—were actually unhealthy according to the criteria. These are people who would likely have higher health costs but who would skate by without added penalties under the new EEOC rules. More alarming, the fallacious assumption that “normal” BMI individuals are healthy could mean they wouldn’t get preventive care or that important diagnoses could be delayed or missed altogether.

Clearly, BMI needs to go. We hope our analysis is the final nail in the coffin for this flawed measure.

But the obsession with BMI is really a symptom of a larger issue: a national infatuation with weight that not only affects how people in power define health, but also perpetuates an entrenched stigma against heavier people. We’ve run many studies in our labs showing that this weight stigma gives rise to situations that make it hard for people to be healthy. We’ve shown, for example, that experiencing weight stigma makes individuals eat more high-calorie snack foods and feel less confident in their ability to maintain a healthy diet. These are things that are bad for you no matter what you weigh.

We’ve also found that people who experience weight stigma have higher levels of the stress hormone cortisol. That’s a problem because cortisol increases a person’s drive to eat foods high in sugar, fat, and calories and sends a signal to the body to start storing visceral fat. That’s a type of fat that sticks to your organs and won’t necessarily make your body bigger, meaning it flies under the radar of BMI. It’s also the type of fat that increases your risk for diabetes and cardiovascular disease.

Our cultural obsession with weight has led us to misguidedly prioritize numbers on the scale over important modifiable health behaviors—eating, exercise, and sleep. Beyond leading us astray from health, this obsession perpetuates the stigma attached to heavier bodies, which is itself an impediment to health.

The evidence is clear: It’s well past time to forget about weight, both as a marker of person’s health and as a marker of a person’s standing in society.


Janet Tomiyama, Ph.D., is an Assistant Professor in the Department of Psychology at the University of California, Los Angeles. She received her B.A. in Psychology in 2001 from Cornell University, and her M.A. and Ph.D. in Social Psychology with concentrations in Health and Quantitative Psychology in 2009 from the University of California, Los Angeles. In 2011. She completed a Robert Wood Johnson Health and Society Scholar Fellowship jointly at the University of California, Berkeley and the University of California, San Francisco. Her research centers around eating, dieting, stress, and weight stigma. See more at


Jeffrey M. Hunger, M.A., is currently a doctoral candidate at the University of California, Santa Barbara where he is working in Dr. Brenda Major’s Self and Social Identity Lab. He also works with Dr. Tomiyama in her Dieting, Stress, and Health Lab at the University of California, Los Angeles. Broadly speaking, his research uses insights from social and personality psychology to understand and improve health and wellbeing. He is particularly interested in the mechanisms by which social and structural conditions (e.g., stigma and discrimination) can undermine health and contribute to group-based health disparities. Much of his current research is focused on testing and refining a theoretical model linking weight-based stigma to poor mental and physical health. See more at



Are you “obese” according to your BMI but perfectly healthy? There is a HERO among us!

Join UCLA’s HEalth Registry of “Obesity” (HERO) and be part of a research study investigating your thoughts, feelings, behaviors, and health.

With your help, the results of this research may help us to understand how everyone – no matter what they weigh – can enjoy good health.

Compensation of up to $100 is provided for your time.

For further information please visit

We note that “obesity” in the title of our study is with the understanding that “obesity” is not an accurate indicator of disease. Indeed, the purpose of HERO is to show that people can be healthy regardless of what number shows up on the scale.

8 Comments to “the HAES® files: Body Mass Index Is Not a Good Measure of Your Health”

  1. While I’m glad to see the BMI get this badly needed critique, I have to say that even if someone is not “the picture of health”, and/or is not making the “correct” food choices like kale, the BMI is not a good marker for health. Nor is kale-eating, nor running. Come to think of it, “health” is so much more than ANY of the physical health markers discussed in this blog entry.

    We have a cultural obsession is not only about weight and it’s relationship to “health” but also with “health” itself. HAES needs to push back against the pressure to perform health rather than join in.

  2. Janet and Jeffrey,

    I am really glad you got this work published – it has been 6 years since Wildman et al. published their similar analysis of the NHANES data, and we are still up to our eyeballs in policy and practice using BMI as a proxy for health. So this is helpful. AND.

    Janet, you and I have talked about this before, but I think it is important to say again that we need to work on the part of the message here that upholds the legitimacy of discriminating based on health itself, even if we agree that BMI is a lousy measure of it. The impulse to defend fat people by saying, hey we don’t ALL fit the stereotypes, leaves the people who do happen to fit the stereotypes in the dust. The bigger problem than discrimination against fat people is the deeper acceptance that people who have worse luck with health should be penalized, that they are morally culpable and that the people who have good luck with their health should not have to care about their struggle.

    “As psychological scientists who study health, we were well-versed in the pitfalls of BMI. We knew we had to push back and illustrate the fallacy of this thinking in such a way that policymakers would understand just how many healthy people would be adversely affected.” OK, but what about the unhealthy people who are affected by getting penalized by higher premiums, or having healthcare withheld, or being forced to diet, or generally having to be exposed to a hostile work environment? Why is that OK, when the ACA was supposed to eliminate discrimination based on pre-existing conditions?

    This argument reminds me of the early days of the AIDS epidemic where distinctions were made between people who got AIDS having sex vs. people who were “innocently” exposed through a blood transfusion. “We’ve also found that people who experience weight stigma have higher levels of the stress hormone cortisol.” People who are less healthy also experience stigma for not performing health, on top of other oppressions that they might face. I would love to see your work expand to include healthism along with weight stigma because I think they are intertwined and intersect with racism, sexism, lack of financial resources, and so on, and fat people have been scapegoated on the basis of lack of health as if this is something legitimate to discriminate against.

    Also, I would like to be able to support your research but I just am not willing to expose anyone to this language of “perfect health” and a potentially stigmatizing experience that divides the world into a health binary that doesn’t exist. I understand why you are trying to document this but as a strategy I think it is weak simply because the opposition always says, “you’re not sick now but just wait. I don’t have to give up my hatred until I see that no one who is fat ever gets sick.” People (of all weights) do tend to get sicker as they age if they don’t die, so why not do research on the ways that the experience of sickness or aging is softened and how our connections ease those burdens, rather than creating yet another boundary around one group that prevents those connections by in-group out-group dynamics and fear of losing privilege?

  3. I applaud getting this article published. I hope it gets lots of attention and wakes some people up. I would love to be part of a data set that seeks to document the health benefits being fat-positive, rejecting weight-loss goals and a weight-based definition of health. But like Deb, I can’t get past the prioritizing of “perfect health.” That’s a small club that throws a lot of people under the bus.

  4. Yes! Thank you so much for shining some much needed light on the fallacies of BMI as a measurement of health. Despite reports that BMI correlates well with risk of early death, it is a poor measurement instrument on its own and health practitioners and policymakers should not use it as a standalone standard to determine overall health. Health goes well beyond what is visible on the outside, namely weight and height, and should include markers of physical, psychological, and emotional well-being.

  5. Agree with what others have said, including thanks for doing this.

    I would like to add one other issue into the realm of possible improvements, which is that a health “risk” is not the same thing as a health problem. Risk is risk, and “risks” of unhealthfulness get conflated with unhealthfulness all the time.

    To put this into perspective, being female is an increased “risk” for getting breast cancer. But just because all females have this increased risk doesn’t mean that no female can possibly be completely healthy.

    An increased “risk” doesn’t even mean for any particular individual that they are going to get whatever they are at “risk” for. Its just an actuarial statistic.

    Likewise, reducing “risks” doesn’t actually make a person healthier, and sometimes can make them less healthy. For example, if I have a BMI that puts me in the “obese” category, I have higher “risks” for diabetes, heart disease, yada yada yada. But if I do unhealthy things to myself to force myself into a lower BMI category, I may be in a lower “risk category” but it does not mean that I am more healthy (as your article notes).

    I think the problem is with conflating “risks” and “health.” Risk factors are just statistical pattern matching. They aren’t health. Health is health. Statistics are statistics. Reducing “risk factors” doesn’t make an individual “healthier” — it just changes their statistical profile, which still is not predictive of anything for any particular individual.

  6. I applaud the study, but also the reservations expressed by the previous commenters. Plus, I have strong reservations about having insurance coverage (such as health insurance) where the unprovable risks can be used as an excuse to charge higher premiums. The concept of insurance works when you pool a large number of insured parties and spread the perceived risks over that pool, so that any individual participant will not face catastrophic expenses–much like the merchant ships for which insurance was invented–which had a habit of sinking and losing their valuable cargo.

    The minute you allow insurers, and/or employers who are helping to pay for premiums, fine-tune their premiums to discriminate against certain participants, ostensibly to promote less risky behaviors, you are on a slippery slope to the promotion of lots of agendas–let’s raise the premiums of those with teenage children, especially boys, who are likely wreck the family car and kill someone; or those who ski on their vacations, as they are more likely to suffer a broken limb; or those who might engage in unprotected sex and acquire an STD–including white, male corporate vice-presidents, by the way. What’s the chance that these individuals will pay higher health insurance premiums, or be forced to attend lectures on risky behavior or face premium increases? No, it is mainly fat people who are fair game for such discrimination.

    • Totally agree. Not to mention that I think it is a fair question to ask, what, and how much of my self/life am I selling to my employer in exchange for my compensation package (including health insurance)?

      When I accept a job, I enter into an agreement with my employer to exchange certain kinds and amounts of work for an agreed-upon amount of compensation. I do NOT enter into an agreement to allow my employer to “manage” my “lifestyle.”

      I may be Old School, and so be it, but I do not believe that just because I have agreed to exchange my labor for a paycheck, it also gives my employer the right to “manage” my “lifestyle” or how I elect to live my life in my non-working hours.

      If they want to say, “Fat people can’t drink soda or eat quiche or whatever during working hours,” fine, I could almost live with that. But managing how I spend my time off the job (“go to the gym!”) or how I spend my household food budget (“eat healthy”), or what I should strive to make my body look like, in my opinion crosses a line that should not be crossed.

  7. That’s great to know expert’s opinion.

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