In 1864, the scientist Benjamin Apthorp Gould was appointed to conduct a survey of the physical characteristics of thousands of Civil War soldiers, sailors, and students. Five years later, what emerged from the published report was a narrative of racial difference. An entire chapter was devoted to lung function: making use of the recently developed spirometer (a measuring device), Gould declared a “very striking” difference between the capacity of Black and white lungs. Gould’s findings were consistent with previous conjectures, where the apparent lower lung function of Black people was part of a justification for enslavement. The report also had a significant legacy, contributing to the establishment of racial difference in lung function as a scientific fact. The assumption that Black people have lower “normal” lung capacity became built into medical practice: a “race correction” in the equation that translates spirometer readings into a measurement of lung function automatically lowered the threshold of “normal” lung function for Black patients. This meant that the same spirometer reading could be categorized as “normal” for a Black patient and “impaired” for a white patient. This “race-corrected” equation was in widespread use and recommended by the American Thoracic Society and European Respiratory Society until 2022.
This vignette tells a well-known story: the history of science and medicine offers up countless examples of the ways in which social values, biases, and assumptions can systematically distort knowledge. Sometimes, it is almost laughably obvious in hindsight: the female disease of hysteria, the classification of homosexuality as a psychological disorder, or the proposition that attempts by enslaved people to escape enslavement was a sign of mental illness (an idea mocked even at the time).
Sometimes, like in the lung function example offered above, an idea becomes reclothed as scientifically respectable, and the influence of outdated or troubling assumptions is only acknowledged much later. Given that prejudice and bias hasn’t gone away, it surely continues to play a distorting role in ways that remain mostly invisible. This might lead one to ask: What is yet to be acknowledged? What distortions are we not yet able to see?
This bring me to the question I want to ask: What do we really know about “obesity”? Some ideas about body size and health are fundamental, extremely widely shared, and taken as basic facts: being fat is bad (unhealthy), losing weight is good (healthy), there is an “epidemic” of “obesity.” These ideas are some of the underlying assumptions of much of the scientific, clinical, and public health research into “obesity”—as well as public understanding. Other ideas that are still common but increasingly challenged, are whether the body mass index (BMI) is a good (or good enough) measure of body size and therefore health risk. This is to say nothing of key claims in particular areas of “obesity” research, like the idea that there is an “obesogenic” microbiome or “obese” metabolism.
The argument I want to sketch here is as follows: first, anti-fatness is the water we swim in. Attitudes of shame, blame, and stigma towards fat bodies have a long history, and continue to be a pervasive feature of societies around the world. This history gives us good reasons to suspect that anti-fatness could be systematically distorting the science of “obesity”—it would be weirder if this thing which pervades public discourse, is promoted by media narratives, profoundly affects our attitudes towards our own bodies, and so on, had no effect on the production of scientific knowledge. Second, studying “obesity” science reveals signs of these distorting effects. I won’t make the case against any specific assumption or claim, but I’ll give a couple reasons to think we should be open to the idea that some of them might be wrong, at least partially. This includes some of those basic facts that seem self-evident to most. In any case, we probably can all agree that getting the science right really matters here, given how key “obesity” science is to medical practice, government policy, public discourse, and individual choices.
Anti-Fatness
What I’m calling anti-fatness could also be called fatphobia, or weight stigma. By anti-fatness I mean discrimination and prejudice directed at people with larger bodies, as well as associated negative attitudes, stereotypes, and biases. Anti-fatness has been observed in societies around the world, and is a consistent presence in media messaging. Anti-fatness has damaging effects in many domains of people’s lives, including in the workplace, home, education, and healthcare. People with larger bodies have been stereotyped as undisciplined, gluttonous, abnormal, less intelligent, undesirable. Historically, negative social narratives of fatness include viewing it as a sign of moral weakness or racial inferiority. In the past few decades, fatness has become increasingly medicalized and understood as a sign of risk of disease, or a disease in itself—a disease of epidemic proportions, that imposes a substantial financial and health burden on society.
There is a growing chorus of voices, from both academia and activism, that have brought to light the various manifestations of anti-fatness, challenging the key assumptions of biomedical and public health models of fatness, and advocated for empowerment and liberation. Of course, the rights of people, regardless of body size, to be treated with dignity and respect and to not be discriminated against, are in no way dependent on the truth of scientific claims about “obesity.” Even if the most committed anti-obesity advocate is right that being fat is unequivocally unhealthy and losing weight is always healthy, moral status does not depend on health. But, given how prevalent and deep-rooted anti-fatness is, wouldn’t we expect it to shape what we think we know?
Is being fat unhealthy?
As Helen Longino and others suggest, a properly functioning scientific community must be able to respond appropriately to criticism. What happens when scientists dissent from fundamental assumptions about “obesity”?
In the year 2000, Katherine Flegal, a senior scientist at the Centers for Disease Control and Prevention (CDC) began working with a team of CDC scientists and statisticians to produce more accurate estimates of the number of deaths associated with “overweight” and “obesity” than those already available. The team identified problems with older studies that included unrepresentative data sets, inaccurate data coding, and failure to adjust for confounding factors. Their study, published in 2005, used more recent and nationally representative data that previous studies, as well as improved statistical methods. So far, so good. The problem was with what the study found: “overweight” (defined by BMI) was associated with (statistically significantly) fewer deaths than “normal weight.” Additionally, the estimate of excess deaths associated with “obesity” was much lower than previous studies.
This seemingly good news—that more accurate estimates indicate that “overweight” and “obesity” are not as dangerous to health as previously thought—did not receive the warm reception one might expect. As described by Flegal, the reaction was fierce: professors of public health disparaged the article in the press, critical flyers were handed out at talks she gave, impromptu speeches criticizing the study were given at conferences. False or misleading criticisms circulated in scientific and public venues: for example, claims that the study had been “recanted,” “retracted,” or “widely discredited” by the CDC found their way into journal articles and Wikipedia entries. However, the article received the CDC’s highest science award.
This is an indication that all is not well in this scientific community. The justification given by some for their vociferous responses was that the study was “dangerous” to the public; that it could create the false impression that it’s okay to be “overweight.” But, given the data calling that very claim into question, why are we so sure this is false? Maybe because to many the idea that being “overweight” or “fat” is unhealthy feels instinctively, obviously true; maybe this is because we internalize the idea that health can be read off the body, where thinness is bound up in desirability, and where what it means to be beautiful and to be healthy are intermingled. Then again, many things that feel true turn out not to be.
Is losing weight healthy?
Epistemic risk comes into science at all stages. In weighing up uncertainty and deciding what to believe or do, how we value potential costs and benefits matters. Health is, presumably, a multifaceted concept which encompasses physical, psychological, and social dimensions. However, anti-fatness produces a world oriented towards weight loss as automatically healthy or even the most important health goal.
As is clear with fad diets that promise rapid weight loss, pursuing weight loss as the primary goal can come at the expense of other health-promoting behaviors. This is true even with more scientifically respectable diets like calorie counting. For example, members of the Reddit forum r/loseit, by and large committed advocates of calorie counting, often downplay or even advise against exercise because it can interfere with weight loss; it’s difficult to burn off as many calories through exercise compared to restricting diet. Studies show that exercise has many benefits to health, even when not accompanied by weight loss. r/loseit members also discuss preferring to eat pre-packaged or processed foods than home-cooked meals because it’s easier to track the calories on the package than add up all the ingredients that go into a recipe.
In any case, the supposedly simple answer, diet and (maybe) exercise, is far from simple: 95% of people who diet to lose weight regain that weight within a few years. Many people become stuck in cycles of dieting, losing and regaining weight over and over. Concerningly, weight cycling may lead to metabolic dysfunction and put people at greater risk of metabolic disease. Drastic weight loss can also have permanent effects on metabolism: a study of contestants on the reality show The Biggest Loser found that the extreme and rapid weight loss they underwent as part of the show resulted in long-lasting slowing of their metabolism, meaning that they had to consume far fewer calories than before to maintain the same weight.
A Scientific American article on the study of The Biggest Loser contestants reports that bariatric surgery appears to avoid similar metabolic consequences. Indeed, until the advent of GLP-1 medications like Ozempic or Wegovy, bariatric surgery was considered to be the gold-standard intervention for “obesity,” i.e. gold-standard in its effectiveness at producing weight loss. Yet, a significant proportion of patients experience negative side effects. This includes physical side effects, such as vitamin deficiencies, hormone dysregulation, and digestive complications. It also includes negative psychosocial effects, including developing alcohol use disorder, eating disorders, and increased risk of suicide and self-harm. Patients experiencing long-term negative health effects following bariatric surgery report feeling dismissed by healthcare providers, feeling trapped in a difficult situation, and not being fully informed before the surgery about the potential lifelong consequences.
GLP-1 receptor agonists, originally developed as treatments for diabetes and later approved for use in weight loss, have been hailed as “wonder drugs” that could revolutionize healthcare. Anti-fatness surely shapes the hype and profitability of these medications, including the proliferation of unregulated sellers offering unlicensed or counterfeit GLP-1 medications without prescription. Data on side effects is still emerging, but may include gastrointestinal complications, disordered eating, vision loss, and significant loss of muscle mass. GLP-1s may well be valuable for some, or many. However, the history of previous weight loss interventions suggest that they can be medically accepted or in public demand even when weight loss comes with significant costs to physical and psychological health. Anti-fatness skews perception of the trade-offs.
What do we really know about the relationship between body size and health? What do we have good reason to believe, and what is more complicated than it seems? The existence of systematic anti-fat bias and indications of its effects on scientific knowledge should lead us to dig deeper, question, and be receptive to the idea that some of what we think we know about “obesity” might be wrong.
The Women in Philosophy series publishes posts on those excluded in the history of philosophy on the basis of gender injustice, issues of gender injustice in the field of philosophy, and issues of gender injustice in the wider world that philosophy can be useful in addressing. If you are interested in writing for the series, please contact the Series Editor Elisabeth Paquette or the Associate Editor Shadi “Soph” Heidarifar.
