Lancet Diabetes & Endocrinology Commission redefines obesity beyond limitations of traditional BMI metrics

Beyond BMI: redefining clinical obesity

Our understanding and treatment of obesity is advancing with time. Body Mass Index (BMI) has traditionally classified individuals into categories such as underweight, normal weight, overweight, and obese. However, a groundbreaking report from The Lancet Diabetes & Endocrinology Commission, which includes international experts and individuals with obesity, introduces a new definition concept that surpasses the limitations of BMI. This shift significantly impacts the approach to managing overweight and obesity, distinguishing when increased fat mass leads to disease. The commission now refers to this as “clinical obesity.” This approach could offer a more precise and targeted strategy for enhancing health and well-being in this complex chronic disease.

The shortcomings of Body Mass Index

For many years, BMI has been the primary method for evaluating obesity. However, BMI alone offers an incomplete view, failing to consider:

• Body fat distribution: BMI does not distinguish between fat, muscle, and bone mass. This limitation can lead to misclassification, such as overdiagnosing individuals with higher muscle or bone mass, like athletes, and underdiagnosing those with excess fat that BMI cannot detect, such as elderly individuals with reduced muscle mass or certain ethnic groups.
• Organ function: BMI does not assess the impact of excess fat on the health of vital organs.
• Individual variability: BMI overlooks the diverse ways in which excess fat affects individuals differently.

The new definition: emphasising health over body composition

The Lancet Commission’s new definition focuses on clinical obesity as a chronic disease caused by the detrimental effects of excess adiposity on bodily functions. Key elements include:

• Objective measurement: Methods beyond BMI, such as waist circumference or body fat percentage, are essential. Assessing the type and distribution of body fat is crucial.
• BMI as a screening tool: While BMI remains useful as an initial screening measure and for population-level studies, it should not serve as the sole determinant for diagnosing obesity.
• Organ dysfunction: Symptoms such as sleep apnoea, joint pain, or cardiovascular issues that indicate impaired organ or tissue function related to excess fat are vital in diagnosis.
• Impact on daily life: Limitations in daily activities caused by obesity are also a critical component of the diagnosis.

Two obesity categories

The commission introduces two categories:

1. Preclinical obesity: Excess adiposity without evident organ dysfunction or activity limitations. Individuals in this category are at increased risk of developing clinical obesity and associated diseases.
2. Clinical obesity: Excess adiposity accompanied by apparent organ dysfunction or activity limitations. This category defines obesity as a chronic disease. Indicators include shortness of breath, joint pain, and metabolic issues such as type 2 diabetes. Individuals can be further classified as “severely obese” based on BMI and associated health risks.

Waist circumference as a health metric

Waist circumference is an important health metric that provides deeper insights into an individual’s risk for obesity-related conditions. According to the World Health Organization (WHO), waist circumference indicates increased visceral fat, which is more harmful than fat stored elsewhere in the body. Recommended cut-offs are:

• Men: 94 cm (37 in) or more
• Women: 80 cm (31.5 in) or more

Unlike BMI, waist circumference accounts for fat distribution. This distinction is crucial as visceral fat, located around abdominal organs, is strongly linked to metabolic diseases. A study published in the Journal of the American Medical Association (JAMA) found waist circumference to be a stronger predictor of mortality than BMI. This underscores the importance of considering body composition and fat distribution in assessing health risks.

Metabolic health and obesity

Metabolic health is fundamental to overall well-being, and obesity significantly increases the risk of metabolic disorders. Even individuals with mild obesity (BMI 25-30) face heightened risks of metabolic syndrome, according to a study in Preventing Chronic Diseases. Assessing metabolic health involves evaluating metrics such as blood pressure, glucose levels, and lipid profiles. A review in Frontiers of Endocrinology found that individuals with normal weight obesity (NWO) — a normal BMI but high body fat percentage — exhibit impaired metabolic health compared to those with healthy weight and composition. This highlights the limitations of BMI and the need for a more comprehensive approach to evaluating obesity’s health implications.

Implications of this new definition

The commission’s new definition could transform obesity care:

• Precise diagnosis: Moving beyond BMI to evaluate overall health comprehensively, including testing for high blood sugar, cholesterol, and other markers.
• Targeted treatment: Strategies that directly address individual health challenges rather than focusing solely on weight loss.
• Improved outcomes: Emphasising organ function and quality of life, promoting sustainable well-being.

Despite its potential, the report has faced criticism for being unclear in its practical applications. Challenges include distinguishing between preclinical and clinical obesity and insufficient attention to mental health in the report. While the intentions are promising, the impact on clinical care remains to be seen.

Yazen’s comprehensive approach to obesity care

At Yazen, we recognise the complexities of obesity and the importance of a holistic approach. Our treatment model supports patients at every stage of their journey through:

• Personalised treatment plans: Tailored plans combining appropriate medication and lifestyle changes to meet individual needs and goals.
• Expert guidance: Access to 24/7 support from doctors, dietitians, psychologists, physiotherapists, and YazenCoaches via our app.
• Sustainable weight loss: Building enduring habits alongside medication to ensure long-term weight maintenance and overall well-being.

By embracing innovative approaches like those outlined by The Lancet Commission, Yazen aims to help individuals achieve sustainable health outcomes and enhanced quality of life.

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Explore the complete Lancet Diabetes & Endocrinology Commission report on the definition and diagnostic criteria of clinical obesity:
The Lancet Diabetes Endocrinology

References:

• Rubino et al 2025. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. Published online.
  
  
• Khan et al. 2023. Surrogate Adiposity Markers and Mortality. JAMA. 6(9):e2334836
  
  
• Shi et al. 2020.The Influence of Metabolic Syndrome in Predicting Mortality Risk Among US Adults: Importance of Metabolic Syndrome Even in Adults With Normal Weight. Prev Chronic Dis. 17:200020
  
  
• Mohammadian et al. 2022. Normal Weight Obesity and Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis. Front. Endocrinol. 13:857930