Goodbye to body mass index: Body fat percentage best predicts risk of death

Obesity is a growing disease in many developed countries , and Spain is no exception. Experts have long warned that its incidence in our country could reach epidemic levels in a few years.

The issue, however, is that determining when a person is overweight or obese is not a simple task. Traditionally, one parameter, the body mass index (BMI), has been used, but it is increasingly being discussed by the scientific community in favor of others such as abdominal circumference or the height-waist ratio.

Fat percentage vs BMI

Now, a new study published in the Annals of Family Medicine has found that another of these parameters proposed as an indicator of overweight and obesity, body fat percentage, is a better predictor of the risk of death from all causes and from cardiovascular disease in individuals between 20 and 49 years of age than BMI.

This is the result of an analysis of data from a population-based cohort of 4,252 adults collected as part of the National Health & Nutrition Examination Survey between 1999 and 2004. The information included body mass index and body fat percentage, obtained in clinical assessments using a bioelectrical impedance device.

In order to explore the relationship between both values ​​and the risk of mortality at fifteen years , they defined a pathological body fat percentage as any value above 25% in men and 44% in women.

A 78% higher risk of death

They found that participants with an unhealthy percentage of body fat had a risk of death in the following fifteen years that was up to 78% higher , and were 2.6 times more likely to die from cardiovascular disease in the same period than those with a healthy percentage.

In contrast, they found no statistically significant relationship between BMI and cardiovascular mortality or all-cause mortality.

These results support the proposal to abandon BMI as the preferred parameter for diagnosing disease and overweight, opting instead for body fat percentage. Furthermore, they serve as a basis for the authors' recommendation to use bioelectrical impedance measurement devices, which are inexpensive.

However, it should be noted that there is currently no scientific consensus on the values ​​that mark the boundary between a healthy percentage of body fat and one that may pose a greater health risk. To establish this boundary, the interrelationship between this parameter and the various pathological aspects of obesity needs to be studied more extensively through prospective studies with large cohorts.

Be that as it may, this work adds to the growing body of scientific evidence that supports replacing BMI (a parameter that, for example, does not take into account the distribution of body mass between muscle and fat tissue) with more precise metrics that more accurately reflect the anatomical and metabolic pathology of obesity.

References

Arch G. Mainous, Lu Yin, Velyn Wu, Pooja Sharma, Breana M. Jenkins, Aaron A. Saguil, Danielle S. Nelson and Frank A. Orlando. Body Mass Index vs Body Fat Percentage as a Predictor of Mortality in Adults Aged 20-49 Years. Annals of Family Medicine (2025). DOI: https://doi.org/10.1370/afm.240330

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