Is Obesity a Disease? Defining Clinical Obesity and Its Treatment

A New Definition of Obesity: Moving Beyond BMI

For years, the medical community has wrestled with a fundamental question: should obesity be categorized as a standalone disease or simply a risk factor for other conditions like diabetes and heart disease? While it’s undeniable that obesity contributes to poor health outcomes, the challenge lies in distinguishing between individuals who are simply overweight and those whose obesity has become a genuine medical concern.

The landscape shifted dramatically in 2023 with the advent of powerful GLP-1 weight loss drugs like semaglutide (marketed as Ozempic). These medications, offering a middle ground between lifestyle changes and invasive surgery, highlighted the need for a clearer understanding of when medical intervention for obesity is truly warranted.

Now, a landmark study by the Lancet Commission, comprised of 56 leading medical experts, is offering a fresh perspective on this complex issue. Their goal: to redefine obesity, separating those who are healthy despite their weight from those whose obesity has become pathological.

Traditionally, Body Mass Index (BMI) has been the primary tool for classifying obesity, with a BMI over 30 signaling obesity. However, BMI has its limitations. Athletes with high muscle mass, for example, can fall into the "obese" category despite being incredibly fit. Furthermore, BMI fails to account for the location of fat storage. Visceral fat, surrounding internal organs, poses a far greater health risk than subcutaneous fat (found just beneath the skin).

The Lancet Commission’s proposed framework addresses these shortcomings. They advocate for a new diagnostic approach called "clinical obesity." This approach employs a two-pronged strategy:

1. Multifaceted Measurements: In addition to BMI, utilizing measurements like waist circumference, waist-hip ratio, or waist-height ratio can offer a more nuanced view. Advanced imaging technologies can even directly assess body fat distribution.
2. Objective Health Indicators: A diagnosis of clinical obesity requires objective evidence of reduced organ function or impaired ability to perform daily activities. This could include difficulty with tasks like bathing, eating, or dressing.

ProfessorFrancesco Rubino, a leading bariatric surgeon and member of the commission, describes this reclassification as a "radical change." The next step, he emphasizes, is identifying the subset of the estimated 1 billion people globally classified as obese under current definitions who might now qualify for the "clinical obesity" diagnosis. Initial estimates suggest this could apply to 20-40% of them.

The Lancet Commission’s framework has already received backing from major health organizations like the American Heart Association and the Chinese Diabetes Society. However, full integration into medical practice and public understanding will take time. This new approach promises to fundamentally reshape how we perceive, diagnose, and treat obesity in its various forms.