Is Waist-to-Hip Ratio a Better Mortality Predictor Than BMI?

This transcript has been edited for clarity.

My name is Irfan Khan and I am a second-year medical student at University College Cork. On September 20, I presented my findings at the annual meeting of the European Association for the Study of Diabetes (EASD) 2022, looking at how waist-to-hip ratio is a stronger, more consistent predictor of mortality compared with body mass index (BMI).

To give a quick background, BMI has been used as a marker for adiposity for a long time, but it has significant limitations. The most significant limitation is that the BMI associated with the lowest risk for all-cause mortality is inconsistent across time, with different ethnicities and populations often falling outside of the recommended 18.5-24.9 normal BMI range. BMI can't differentiate fat mass from lean mass, or subcutaneous or good fat vs visceral fat or bad fat.

With these limitations of BMI in mind, we wanted to determine what is that optimum biomarker of adiposity for predicting mortality or disease risk, given that it wasn't clearly BMI. We wanted to find a measure that was causal rather than correlational, strong in terms of its association with mortality, and a measure consistent across variation in fat distribution and easy to assess.

Our main finding was that compared with BMI or fat mass index (a marker for pure fat adiposity without the other components that BMI would otherwise entail, such as water mass or lean mass), waist-to-hip ratio was a stronger predictor for all-cause mortality, and it was consistent in its association with mortality across variations in BMI.

The main message from our study, therefore, is that the focus should now be on fat distribution as opposed to weight. If you think about it, depending on an individual's body composition, someone might actually benefit from a higher or lower BMI. With our study, that's not necessarily the case with waist-to-hip ratio. Our study demonstrates that a lower waist-to-hip ratio will always result in a lower mortality risk without any nuance.

In terms of my recommendations for clinicians, even though our study doesn't necessarily confirm the replacement of BMI with waist-to-hip ratio, I would advise clinicians to consider measuring waist and hip circumference if a patient is curious as to whether or not they're at a healthy weight.

Even after using BMI, getting the waist-to-hip ratio can give the most holistic answer to the question of whether or not they're at a healthy weight or at high risk for mortality.

Overall, waist-to-hip ratio, a simple adiposity measure, should be encouraged and adopted in the clinic.

If you have any other questions, feel free to contact me or the corresponding author for our project, Dr Guillaume Paré. Thank you.

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Cite this: Is Waist-to-Hip Ratio a Better Mortality Predictor Than BMI? - Medscape - Oct 12, 2022.

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