In recent decades, an increasing number of expert organizations have shifted away from viewing obesity as a simple problem of eating too much and moving too little. Instead, organizations like the American Medical Association now classify obesity as a disease.
While some experts insist that this designation has advanced research and fostered more collaborative care, others contend that it prioritizes the booming obesity drug market over the needs of patients.
On January 14th, 2025, new guidelines were introduced that potentially lend greater significance to the disease designation—though their impact remains to be seen.
The New Disease Definition
On January 14, the new guidelines, endorsed by 76 medical organizations, were published in the Lancet Diabetes and Endocrinology. The guidelines reaffirm obesity’s classification as a disease while updating its diagnostic criteria.
Rather than relying solely on body mass index (B.M.I.)—a simple ratio of height to weight—experts now recommend that healthcare providers assess the impact of excess fatty tissue on overall health. Under the updated guidelines, clinical obesity is defined as a condition in which excess fat disrupts normal organ activity, causing symptoms such as shortness of breath, joint pain, reduced range of motion, and kidney issues. Individuals with excess fat but no current symptoms may be classified as having preclinical obesity, indicating a heightened risk of future complications.
The recommendations suggest that while those diagnosed with obesity should receive treatment, individuals with preclinical obesity should be monitored and potentially counseled on weight loss but otherwise left untreated.
If widely embraced, these guidelines could enable doctors to deliver more precise diagnoses and tailored treatments. But does this intense focus on the markers of obesity risk sidelining the critical need for prevention?
The Case for Defining Obesity as a Disease: More Resources and Better Treatment
Defining obesity as a disease has allowed doctors and scientists to devote more resources to studying the biological, psychological and social causes and effects of the condition, explains Steven Shamah, M.D., Director of Endoscopy at Lenox Hill Hospital in New York City.
“Obesity is a chronic, progressive and relapsing disease,” says Matthew Landry, Ph.D., assistant professor of population health and disease prevention at the University of California Irvine and spokesperson for the Obesity Society, a professional society focused on obesity science, treatment and prevention. “It is not simply a lifestyle choice or some kind of moral failing, but a disease. It’s a medical condition that we recognize now as involving multiple biological, genetic and environmental factors that all regulate our body’s energy usage and, ultimately, our body weight.”
Our Changing View of Obesity: From ‘Poor Choices’ to Chronic Disease
A dramatic push to redefine obesity started to gain steam in the late 1990s, notes Dr. Shamah.
“Before the 90s,” says Dr. Shamah, “the blame had been put on the patient. ‘You eat too much. You don’t make the right choices.’ And it really came from a poor understanding of the disease process.”
As early as 1948, the World Health Organization recognized obesity as a disease, but the distinction didn’t start to catch on until decades later. In 1998, the National Institutes of Health (NIH) released a guideline for identifying, evaluating and treating obesity. The Obesity Society got on board the obesity-as-a-disease train in 2008, 10 years after the NIH guideline was published.
Later, in 2013, the American Medical Association gave one of the strongest endorsements of defining obesity as a disease, releasing a resolution titled “Recognition of Obesity as a Disease.”
The authors of the statement laid out the hormonal and metabolic characteristics frequently associated with obesity and the chronic conditions a person with obesity has a heightened risk of experiencing, such as diabetes. It also plainly stated that “the suggestion that obesity is not a disease but rather a consequence of a chosen lifestyle exemplified by overeating and/or inactivity is equivalent to suggesting that lung cancer is not a disease because it was brought about by individual choice to smoke cigarettes.”
According to Dr. Shamah, that endorsement created an “overnight explosion of research,” helping researchers identify a variety of genes and hormones that influence a range of mechanisms, such as hunger, fullness, and how our bodies process and store fat. Correlations between exposure to certain environmental chemicals and the likelihood of someone having obesity have also been found.
How The Disease Model Changed Obesity Treatment
Alongside a deeper understanding of the condition, experts note that the obesity-as-a-disease model has also helped emphasize the importance of a holistic treatment plan.
“Medical providers are understanding it’s a lot more complex than calories in vs. calories out, that there’s a number of factors that all regulate our weight, whether it’s our hunger and satiety cues, or some [other] kind of neurological process,” says Dr. Landry. “Medical providers are now coming into these patient care appointments and really trying to unpack the root cause [of that person’s obesity] and taking more of an individualized approach.”
At Lenox Hill, Dr. Shamah agrees that the designation has allowed a multidisciplinary team to come together. “We have a more collaborative approach between all clinicians and dieticians and psychologists to really help treat this multifactorial, complex disease,” he explains.
Indeed, the disease model should change how a healthcare provider approaches each appointment, continues Dr. Landry. Providers should ask detailed questions about how the patient has attempted to lose weight in the past. With that information, Dr. Landry says, the doctor should go on to develop a more personalized plan.
“We now have a number of different interventions that we can use with someone, whether that’s pharmaceutical treatments, or a more diet and lifestyle-based approach. When a physician is able to look at obesity as this complex disease, they can identify what might be the best treatment option.”
The Case Against Defining Obesity as a Disease: Social Factors and Weight Loss Medications
While new treatments and shifting attitudes may improve access to care for those living with obesity, at least one physician argues that the medical establishment’s focus on treatment over prevention has allowed Big Pharma to profit from an endless cycle of interventions.
Obesity as a Disease ‘Invites’ People to Drown, Says Doctor
About a year after the AMA first endorsed the disease model of obesity, David L. Katz, M.D., an internist and preventive medicine specialist at Yale University, penned a perspective piece for Nature saying that the designation was a mistake and overlooked society’s need for prevention.
When contacted for this article, Dr. Katz noted via email that “my views have not changed. I continue to advocate for treating obesity as a form of drowning rather than a disease.”
Drowning, he explains, is an example of what happens when the body becomes incompatible with its environment—such as being underwater. Since the human body is not designed to function in such conditions, the real solution is to change the environment by getting to dry land, rather than attempting to survive by taking oxygen in pill form while still submerged.
In our society, he continues, “we simply invite, if not encourage, everyone to drown; then blame them for drowning. Then invoke treatment after prevention has been thoroughly neglected,” he notes.
Instead of focusing all of our resources on treating obesity after it has developed, Dr. Katz continues, we should focus on preventing the condition by providing easy access to and education about healthy foods rather than highly processed “junk.”
Identifying obesity as a disease also sets the stage for the marketing and prescribing of significant quantities of medications to help people lose weight. These drugs, like Wegovy and Ozempic, are meant to be taken long-term and, like any drug, come with side effects. But they appear to be very effective at helping people drop pounds, and now, Dr. Katz worries, “we seem to have forgotten about prevention entirely.”
Despite Disease Designation, Weight Stigma Still Exists
While experts like Dr. Landry and Dr. Shamah, along with recent research, suggest there is growing provider understanding and acceptance when patients seek weight-loss solutions, the reality is that many doctors continue to hold deeply ingrained prejudices.
And those prejudices can do real harm.
For instance, in a feature on physicians and weight stigma, a woman with obesity told STAT News that her doctors repeatedly dismissed symptoms that were later diagnosed as lung cancer. Instead, they attributed her respiratory issues to bronchitis, acid reflux, and other conditions, and told her losing weight would help.
In another STAT article on weight stigma, a woman living with overweight who was dealing with worrying, unexplained weight loss says she was dismissed by a gynecologist who decided nothing was wrong with her. After having such a negative experience, she’d put off seeking a second opinion. By the time an internist found the endometrial cancer causing her weight loss, the mass had metastasized. She died six months later.
“Even though we’ve moved to this disease model of obesity, we still have some providers, or even just individuals, that still put a lot of blame on themselves. And that weight stigma is still there,” admits Dr. Landry.
Despite some dissenting voices, the January 14th recommendations likely bolster the growing dominance of the obesity-as-a-disease model. Yet both advocates and critics agree on one essential point: the pivotal role of environmental factors in shaping obesity risk—particularly as the rise of weight-loss medications threatens to treat patients as a homogenous group, rather than as individuals with distinct health profiles, histories and circumstances.
“We can do a much better job of understanding that there’s influences, like the food system or environment, or even just how healthcare is delivered, that certainly influences someone’s health outcomes,” says Dr. Landry. “The patient’s voice always needs to be put at the center of our understanding of obesity.”
