Body Fat Percentage More Accurate than BMI for Predicting Obesity-Related Health Risks, Study Shows

In a recent study published in the Journal of Clinical Endocrinology & Metabolism, researchers evaluated body fat percentage thresholds to define overweight and obesity, examining their correlation with metabolic syndrome.

Typically, BMI is used to define obesity and overweight, but it is an imprecise measure of body fat percentage (%BF). Modern technologies have improved body fat percentage estimation, but outcome-based body fat percentage thresholds are needed to guide patient health effectively.

Previous correlations of body fat percentage with health risks using BMI have been imprecise due to factors like sex, age, and fitness. Obesity-related diseases are linked to excess adiposity, yet current weight recommendations often rely on generalized mortality statistics. New methods like multifrequency bioelectrical impedance (MF-BIA) offer more accurate body fat percentage estimation and could improve the management of obesity-related diseases compared to BMI.

In the study, correlational analyses were conducted using data from the National Health and Nutrition Examination Survey (NHANES) to evaluate body fat percentage thresholds for defining overweight and obesity. The sample consisted of 16,918 individuals aged 18 to 85, with data collected between 1999 and 2018, excluding periods without dual-energy x-ray absorptiometry (DXA) measurements. Data included demographics, laboratory measures, body measures, and whole-body DXA assessments.

The results showed that among overweight individuals (BMI >25 kg/m²), 5% had metabolic syndrome, while among obese individuals (BMI ≥30 kg/m²), this proportion increased to 35%. New body fat percentage thresholds were established: 25% for overweight and 30% for obesity in males, and 36% for overweight and 42% for obesity in females. Using these thresholds, a significant portion of both men and women were classified as overweight or obese.

The study emphasized the poor predictive value of BMI due to variability in body fat percentage at any given BMI, highlighting the limitations of BMI in assessing adiposity and associated health risks, particularly across genders.

The findings suggested that body fat percentage thresholds are superior to BMI in predicting obesity-related health issues. It recommends using direct adiposity measurements in clinical practice, proposing thresholds of 25% BF for identifying overweight in men and 36% BF in women.

Reference: Defining overweight and obesity by percent baody fat instead of body mass index. Potter, A.D., Chin, G.C., Looney, D.P., Friedl, K.E. The Journal of Clinical Endocrinology & Metabolism (2024). DOI: 10.1210/clinem/dgae341, https://academic.oup.com/jcem/advance-article/doi/10.1210/clinem/dgae341/7673666