Obesity is a disease, not a choice. It is a medical condition influenced by genetic, environmental, psychosocial, cultural, lifestyle, and other factors. Obesity is a risk factor for heart disease, stroke, high blood pressure, type 2 diabetes, obstructive sleep apnea and osteoarthritis, just to name a few co-occurring conditions, and it is a standalone condition for which treatment is imperative.
These statements, however uncontroversial, were not reflected in medical guidelines and protocols until quite recently. It wasn’t until 2013 that the American Medical Association defined obesity as a disease, 15 years after the National Institutes of Health (NIH) declared it so following the breakthrough discovery of leptin.
As the sweeping success of the new GLP-1 drugs dramatically transforms the landscape of obesity treatment today, experts continue to refine and improve medical definitions of obesity in an effort to more accurately diagnose and more effectively treat the condition.
Last year, the Lancet Diabetes & Endocrinology Commission, a group of 58 international experts representing multiple medical specialties, developed a set of definitions and diagnostic criteria for obesity. The commission redefined obesity as a disease in and of itself, highlighted its complex causation, and questioned the utility of BMI alone as an assessment tool. Using these criteria as guidance, physician groups, like the American Association of Clinical Endocrinology, have published consensus statements of their own.
While the consequences of these changes in definition and diagnosis are still unfolding, the impact is being felt. To understand what these changes mean for you, we’ve unpacked the top takeaways here.
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Obesity is a disease, not a risk factor.
Obesity was long considered a risk factor for other diseases, including heart disease, diabetes, and cancer. Before your cholesterol began to climb, for example, your doctor likely did not flag your weight as a concern.
The Lancet Commission’s stance marks a clear break from that perspective. It firmly states that obesity is a chronic disease on its own and, as such, requires long-term management and treatment. Excess fat tissue can cause direct damage to your organs and tissues, and it should be proactively addressed.
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Clinical obesity is a new — and controversial — concept.
Rather than existing as passive deposits, fat cells function as an endocrine organ, releasing a range of hormones, including leptin, that regulate metabolism and appetite. But when excess fat accumulates, especially in the abdominal area, it starts to become dysfunctional, leading to insulin resistance, chronic low-grade inflammation, a buildup of fat in organs such as the liver, and cardiovascular changes.
The commission advocated for a new diagnostic category called clinical obesity, which requires evidence of reduced organ or tissue function due to obesity. Evidence may comprise signs, symptoms, or diagnostic tests showing abnormalities or serious limitations to daily activities.
The commission also recommended a preclinical obesity designation referring to obesity in which function of tissues and organs is preserved. Preclinical obesity, it noted, increases the risk of developing clinical obesity and other diseases, including type 2 diabetes and cardiovascular disease.
Not all experts agree on separating clinical and preclinical obesity, and some worry that this categorization may prevent access to much needed care.
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Obesity has complex causes.
When obesity is conceived of as a lifestyle issue, the solution appears simple: change diet, exercise, and other behaviors. However, decades of research confirms that obesity is caused by a combination of genetic, biological, environmental, psychological, nutritional, and metabolic factors — and the Lancet Commission states this clearly. Losing weight is hard because many forces, from your genes and metabolism to social and economic factors, are exerting force in the opposite direction.
“It’s not a cosmetic problem, or a willpower problem,” says Marc-André Cornier, MD, president of the Obesity Society and director of endocrinology, diabetes and metabolic diseases at the Medical University of South Carolina. “There’s abnormal biology, a genetic predisposition; and, in the right environment, it comes out,” he says.
Recognizing obesity as a multifactorial chronic disease invites the dismantling of self-blame and stigma, which stands in the way of treatment for many people. “Tackling stigma is not only a matter of social justice,” the Lancet Commission writes, “But a way to advance prevention and treatment of obesity and reduce associated illness and mortality.”
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BMI isn’t always the best way to assess obesity.
Historically, obesity has been diagnosed based on your body mass index (BMI), a calculation of weight and height. But BMI is a crude estimate of obesity, at best. It can’t distinguish between fat and lean muscle tissue, or between dysfunctional fat, likely to accumulate around your waist, and fat that is less harmful.
The Lancet Commission highlights something that many obesity experts have long witnessed: “Many of us are concerned that BMI underdiagnoses people,” says Cornier. “Many people have lower BMI and higher risk of adiposity. We’re concerned with the individual with a BMI of 26, who has central obesity but is not being diagnosed.”
The Lancet Commission shifts the diagnostic focus to abdominal fat, recommending the use of waist circumference or waist-to-height ratio to assess obesity. The exception is people with a BMI greater than 40 because obesity is assumed without additional measurements needed.
This shift could invite a surge of diagnoses. A study of 301,026 U.S. adults found that, according to BMI-only measures, 43% of the group had obesity. Using the new criteria, that number jumped to 69%. One in four people who did not meet criteria for the condition previously were reclassified as having obesity when evaluated using the new measurements. The diagnosis was more common among certain ethnic groups, like people of South Asian descent, who are more prone to abdominal fat.
Most primary care physicians continue to diagnose obesity based on BMI, but if you have an apple-shaped body or have gained weight around your waist, it may be advisable to ask your doctor about measurements such as waist circumference or waist-to-height ratio as well.
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Obesity should be treated.
The advent of GLP-1 agonist medications has led to scores of people with obesity receiving medical treatment. About 1 in 8 U.S. adults say they have taken or are taking GLP-1 drugs for obesity, diabetes, obstructive sleep apnea, or another chronic condition. While that number is arresting, it falls far short of matching the number of individuals who have obesity, which is an estimated 40% of U.S. adults. This means that a huge number of people are still not receiving potentially life-saving care, which can include a GLP-1 or other medication, nutritional help, lifestyle coaching, mental health services, and/ or bariatric surgery.
