What Is the Role of the New Index Relative Fat Mass (RFM) in the Assessment of Nonalcoholic Fatty Liver Disease (NAFLD)?

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Nonalcoholic fatty liver disease (NAFLD) is the liver manifestation of adiposopathy. Recently, a new score was developed to estimate body fat percentage (relative fat mass, RFM). We aimed to evaluate the value of RFM in predicting the presence and severity of NAFLD, compared with other anthropometric measurements.


RFM, body mass index (BMI), and other anthropometric measurements were evaluated in two cohorts of subjects: a cohort from a Portuguese prospective epidemiological study (e_Cor) and morbidly obese patients with biopsy-proven NAFLD. We evaluated if RFM and BMI were related with the presence and severity of liver disease, which was assessed by noninvasive tools in the first cohort and by liver histology in the morbidly obese cohort. The independence of relations found in univariate analysis was assessed with multivariable logistic regression analysis.


In the general population cohort, 744 subjects (48% male) were enrolled. BMI-defined obesity was present in 23% and RFM-defined obesity in 86%. Insulin resistance (IR) related with BMI-defined obesity (OR 4.37 [2.16–8.84]) and weight (OR 1.05 [1.02–1.08]) in men, and waist circumference (WC) (OR 1.07 [1.03–1.11]) in women. Dyslipidemia and hypertension related with RFM-defined obesity in men (OR 2.96 [1.36–6.47] and OR 5.37 [1.31–22.06], respectively). Ultrasound-diagnosed NAFLD in 33% related with weight in men (OR 1.03 [1.003–1.06] and WC in women (OR 1.06 [1.02–1.10]). In men, ALT elevation related with weight (OR 1.04 [1.02–1.07]). In women, advanced fibrosis (estimated by NAFLD Fibrosis Score) associated with BMI-defined obesity (OR 42.43 [3.61–498.13]). In the morbidly obese cohort, 152 subjects were enrolled, of whom 84% were female, 37% had steatohepatitis, and 9.4% had advanced fibrosis. Adiponectin associated inversely and leptin positively with RFM in men. The severity of steatosis increased linearly with BMI and WC in women. Higher BMI associated with steatohepatitis in women and advanced fibrosis in men.


RFM-defined obesity better predicted dyslipidemia and hypertension (though not IR) and adipokine imbalance; however, it did not add value to BMI-defined obesity in predicting NAFLD or liver injury.

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Fig. 1



Alanine aminotransferase


Body mass index


Dual-energy X-ray absorptiometry


Enzyme-linked immunosorbent assay


Homeostasis model assessment of insulin resistance


Insulin resistance


Nonalcoholic fatty liver disease


Relative fat mass


Waist circumference


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Correspondence to Mariana V. Machado.

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The study was approved by the Hospital Santa Maria Human Ethics Committee. The study protocol conformed to the ethical guidelines of the 1975 Declaration of Helsinki, revised in 2000.

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Informed consent was obtained from all individual participants included in the study.

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Machado, M.V., Policarpo, S., Coutinho, J. et al. What Is the Role of the New Index Relative Fat Mass (RFM) in the Assessment of Nonalcoholic Fatty Liver Disease (NAFLD)?. OBES SURG 30, 560–568 (2020).

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  • Nonalcoholic fatty liver disease, Obesity, Relative fat mass