Redefining Obesity: A New Clinical Approach

This document summarizes key findings and recommendations regarding a new way to define and diagnose obesity, as proposed by the Lancet Diabetes & Endocrinology Commission. The core argument is that Body Mass Index (BMI) is an inadequate tool for diagnosing and understanding obesity. The commission proposes a shift in focus from solely weight and BMI to a more comprehensive approach that considers the level and distribution of body fat, along with the presence of associated health problems. This new definition categorizes obesity into two states: “clinical obesity” (with existing health problems) and “pre-clinical obesity” (high levels of fat but without current illness). This new approach aims to personalize treatment, reduce stigma, and improve resource allocation.

Key Themes and Ideas:

1. Limitations of BMI:

• The traditional reliance on BMI (weight in kilograms divided by height in meters squared) for defining obesity is flawed.
• “The risk to health and wellbeing is not determined by weight – and therefore BMI – alone.”
• BMI doesn’t account for the relative percentages of fat, bone, and muscle, which can lead to misclassification. For example, athletes with high muscle mass might be categorized as obese based on BMI alone, even if they’re healthy: “Athletes with a relatively high muscle mass, for example, may have a higher BMI. Even when that athlete has a BMI over 30 kg/m², their higher weight is due to excess muscle rather than excess fatty tissue.”
• BMI does not provide insight into the distribution of fat, which is critical for health risk. Specifically, abdominal fat poses higher risks because it can release damaging molecules into the bloodstream. “People who carry their excess fatty tissue around their waist are at greatest risk of the health problems associated with obesity.”
• Using BMI alone can lead to both false positives and false negatives: “People with excess body fat don’t always have a BMI over 30, meaning they are not investigated for health problems associated with excess body fat.” and “… others who aren’t athletes but have excess fat may have a high BMI but no associated health problems.”

1. New Definition and Diagnostic Categories:

• The Lancet Commission proposes that “having a larger body shouldn’t mean you’re diagnosed with “clinical obesity.” Such a diagnosis should depend on the level and location of body fat – and whether there are associated health problems.”
• The new framework includes two categories:
• Clinical Obesity: Characterized by “signs and symptoms of ongoing organ dysfunction and/or difficulty with day-to-day activities of daily living”. This is a condition where the excess body fat is actively causing health problems. Examples of diagnostic criteria include breathlessness due to obesity’s effects on the lungs, obesity-induced heart failure, raised blood pressure, fatty liver disease, and movement limitations. There are 18 such criteria for adults and 13 for children/adolescents.
• Pre-Clinical Obesity: Defined as having “high levels of body fat that are not causing any illness”. Individuals in this category have higher fat levels but can perform daily tasks without impairment and have no overt signs of reduced organ function. However, they are at a higher risk of developing health issues. “People with pre-clinical obesity are generally at higher risk of developing diseases such as heart disease, some cancers and type 2 diabetes.”

1. Implications for Treatment:

• The treatment approach should differ based on these categories.
• Clinical Obesity: Requires access to healthcare and “the focus of health care should be on improving the health problems caused by obesity.” Treatment options include behavior change support, obesity-management medications, and metabolic bariatric surgery.
• Pre-Clinical Obesity: Focuses on risk reduction and prevention. “For those with pre-clinical obesity, health care should be about risk reduction and prevention of health problems related to obesity.” This may include health counseling, monitoring over time, and, depending on individual risk, may involve any of the treatments for Clinical Obesity.
• The new definition should facilitate more personalized, cost-effective healthcare for people with obesity. “Distinguishing people who don’t have illness from those who already have ongoing illness will enable personalised approaches to obesity prevention, management and treatment with more appropriate and cost-effective allocation of resources.”

1. Importance of Reframing the Narrative of Obesity:

• A crucial element of this new approach involves addressing stigma and misunderstandings about obesity. “Reframing the narrative of obesity may help eradicate misconceptions that contribute to stigma, including making false assumptions about the health status of people in larger bodies.”
• The document calls for the public to develop “A better understanding of the biology and health effects of obesity” so that people with larger bodies are not automatically “blamed for their condition.”
• People with obesity should be given personalized, “evidence-based assessments and advice, free of stigma and blame”.

1. Next Steps:

• The proposed criteria should be adopted into national and international clinical guidelines.
• Healthcare professionals, service managers, and the general public need to be educated about these new definitions and diagnostic criteria.

Conclusion:

The Lancet Commission’s proposal represents a significant shift in understanding and addressing obesity. Moving beyond BMI and focusing on the health consequences of excess body fat will lead to more targeted and effective care. This framework aims to destigmatize obesity, improve patient outcomes, and optimize healthcare resource allocation. It stresses the need for a more nuanced, personalized approach to diagnosing and treating obesity, and promotes a focus on prevention and risk reduction for those with pre-clinical obesity. The new system also stresses that people with larger bodies are not responsible for their condition and deserve respectful, evidence-based treatment.