Bye bye, BMI?

A forward-looking view ...

You may have seen the news; The Lancet Diabetes & Endocrinology Commission has proposed a new method of defining obesity that goes beyond Body Mass Index (BMI)¹. It is no secret that BMI has been a cornerstone of life insurance underwriting globally. This number: your weight divided by your height squared can influence insurance outcomes. But the truth is, BMI can often be an imperfect tool when used in isolation.

The latest obesity guidelines¹ deliver a shift in clinical medicine with new definitions and assessment of obesity. This provides health care professionals a framework to stratify obesity risk with the intent to improve health outcomes.

The new framework proposed by The Lancet makes a distinction between:

1. Pre-clinical Obesity - Excess body fat is present, but there is no measurable impact on health yet.

2. Clinical Obesity - Excess fat is affecting organ function, causing disease, or impairing daily life.

The guidelines emphasize measures beyond BMI to better assess obesity, including:

• waist circumference
• waist-to-hip ratio
• metabolic health markers

Importantly, they remind us that BMI can be seen as a surrogate measure of health risk, and that there are more factors to consider in risk assessment.

This clinical approach now more closely aligns to Swiss Re's underwriting approach to cardiometabolic risks.

The appeal of BMI in underwriting has always been its simplicity. It provides a quick, standardized way to classify applicants into risk categories, similarly to the World Health Organization's ² BMI definition used to classify underweight, overweight and obesity in adults. Generally speaking, the higher the BMI, the higher the assumed health and mortality risk.

But simplicity has its downsides. BMI does not differentiate between muscle and fat, nor does it account for fat distribution, metabolic health, or other key factors that impact longevity. These supplementary key factors enhance and balance the overall underwriting assessment to make room for scenarios where BMI is the only factor of concern. In practice, when BMI is used as the sole metric in an insurance assessment it can overestimate or underestimate risk, particularly when applied to large age bands for classification.

While insurers can include waist circumference as a metric to augment BMI risk differentiation, leading to a more precise view of risk, it may not yet carry enough weight. This is why at Swiss Re we account for and indeed encourage use of waist circumference and other metabolic health markers in Life Guide as this creates the possibility of more targeted outcomes for the applicant via 'credits' or additional 'debits'.

The question remains: do we need to go further?  Do we start using waist-to-hip ratios as an optional input in our risk calculations? Or should waist-to-hip ratios and waist circumference be a mandatory requirement? These are all open questions and require further consideration in context of changes to processes, balancing operational costs, educating distribution channels on benefits to consumers, etc.

I believe BMI will remain part of the underwriting equation but ponder: are its days as the sole measure of obesity risk numbered? The question for me is not whether the industry will adapt, but when. Insurers will have a lot to consider in the future, especially with newer wearable or phone technologies available to assess health metrics like weight. We could close the gap between medical record and self-disclosed weight misalignment.

My final call to action is for underwriting leaders, product development teams and individual underwriters to keep advocating for the end consumer. Swiss Re's Metabolic Health initiatives hope to improve insulin resistance for our policyholders, and along with it weight and BMI. New underwriting and product designs incorporating these Metabolic Health programs could expand the risk pool by offering lower and more affordable premiums to those with excessive BMI or poor metabolic health if they commit to a program and there is evidence of sustained health improvement.