BMI alone doesn’t tell the full story of obesity. Discover why experts recommend additional metrics like waist-to-height ratio, body composition scans, and new obesity classifications for a more accurate health assessment.

Key takeaways

• BMI is an incomplete measure that does not account for fat distribution, muscle mass, or metabolic health and can lead to misclassification.
• More accurate metrics such as waist-to-hip ratio, waist-to-height ratio, and body composition scans provide a clearer picture of obesity-related risks.
• Obesity classification is evolving with experts proposing clinical obesity for those with health issues and pre-clinical obesity for those at higher risk but without symptoms.

Body Mass Index (BMI) has long been the standard metric for diagnosing obesity. By comparing weight to height, BMI categorises individuals into ranges like “normal weight,” “overweight,” or “obese.” However, experts increasingly argue that BMI oversimplifies obesity and fails to capture its complexity. Instead of relying solely on this one-dimensional measure, they recommend a more comprehensive approach that includes additional metrics to provide a fuller picture of health risks.

Why BMI Falls Short

BMI does not distinguish between fat mass, muscle mass, or where fat is distributed on the body. It also overlooks other factors like metabolic health, genetics, and lifestyle. While BMI can provide a general indication of health risk, it may misclassify some people. For example, an athletic person with high muscle mass could be categorised as overweight, while someone with a normal BMI but high abdominal fat might still face significant health risks.

Beyond BMI: Key Metrics to Assess Obesity

To address these limitations, experts recommend incorporating the following measures:

Waist Circumference

This simple metric measures abdominal fat, which is closely linked to the risk of metabolic diseases.

Ideal Waist Circumference

• Women: Less than 80 cm
• Men: Less than 94 cm

Waist-to-Hip Ratio (WHR)

This metric compares the circumference of your waist to your hips, providing insight into fat distribution and cardiovascular risk.

Ideal WHR

• Men: 0.9 or less
• Women: 0.85 or less

WHR of 1.0 or higher increases the risk of heart disease and other conditions.

Waist-to-Height Ratio (WHtR)

A newer measure that may be a better predictor of health outcomes than BMI. Divide your waist circumference by your height (both in cm) to calculate the ratio.

Risk Levels

• Low Risk: 0.4 to 0.49
• Moderate Risk: 0.5 to 0.59
• High Risk: 0.6 or higher

Body Composition Scans

These scans measure fat mass, muscle mass, and bone mass, offering a detailed understanding of body composition.

Normal Fat Mass

• Women: 25–31%
• Men: 18–24%

Higher fat mass is associated with increased adiposity and greater risk of inflammatory diseases such as cardiovascular disease, type 2 diabetes, and stroke.

Redefining Obesity: Clinical and Pre-Clinical Categories

Experts propose introducing two new categories of obesity: clinical obesity and pre-clinical obesity. These categories shift the focus from weight alone to a broader understanding of health and risk.

Clinical Obesity

This category includes individuals with clear obesity-related health issues, such as breathlessness, joint pain, or heart failure. It recognises obesity as a chronic condition with significant impacts on health and daily life.

Pre-Clinical Obesity

This applies to individuals who do not yet have obesity-related illnesses but face a higher risk of developing them. While they may not show physical symptoms, they are at elevated risk for conditions like heart disease, stroke, and type 2 diabetes.

The Debate: Is Obesity a Disease?

The classification of obesity as a disease has been debated for years. Some argue it is a risk factor for other conditions, while others see it as a chronic disease requiring medical intervention.

Professor Rubino, Chair of the Global Commission on Clinical Obesity, offers a more nuanced view:

‍“The question of whether obesity is a disease is flawed. Obesity can act as a chronic condition with pathological consequences in some cases.”

Dr Terri-Lynne South agrees, highlighting the complexity of obesity. She believes the new categories will help practitioners address both the risks and the chronic nature of obesity more effectively.

Toward Better Care and Outcomes

The Global Commission’s recommendations aim to improve how obesity is managed by focusing on personalised, evidence-based care. A comprehensive approach to obesity goes beyond BMI and includes metabolic health. Research shows that stabilising glucose levels can support weight management by improving fat metabolism and reducing cravings.

Dr South emphasises that these changes may destigmatise obesity, leading to better patient outcomes.

The use of tools like continuous glucose monitors (CGMs) and personalised health data holds great promise. These advancements could revolutionise how we manage obesity and related conditions, improving both physical and mental health for millions of people.

By expanding the metrics used to assess obesity, healthcare providers can gain a more accurate understanding of individual health risks, paving the way for tailored interventions that make a real difference.

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