CUN-BAE Index as a Screening Tool to Identify Increased Metabolic Risk in Apparently Healthy Normal-Weight Adults and Those with Obesity

Abstract

Background: Imbalanced dietary intake is related to increased adiposity, which is linked to increased metabolic risk even in the absence of obesity. BMI is traditionally used to classify body fatness and weight range, but it only considers body weight and height. The Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE) equation has appeared as an additional tool to estimate adiposity considering also other relevant parameters, i.e., sex and age.

Objectives: We aimed to determine whether the CUN-BAE index could estimate adiposity-related metabolic risk in apparently healthy, normoglycemic adults.

Methods: In this case-control study, men and women (18-45 y old) were classified as normal-weight (NW) [n = 20; BMI (in kg/m2) <25] or overweight-obese (OW-OB) (n = 34; BMI ≥25). The primary outcome was body fat content and clinical circulating parameters to assess by correlation analysis CUN-BAE's usefulness as a predictor of metabolic risk. In addition, transcriptomic biomarkers of lipid metabolism were analyzed in peripheral blood mononuclear cells (PBMCs) as secondary outcome indicators of metabolic impairment. Data were analyzed by correlation analysis and comparison of means.

Results: CUN-BAE values correlated directly with body fatness obtained by DXA (r = 0.89, P < 0.01), with classical molecular biomarkers of metabolic risk, and with PBMC gene expression of carnitine palmitoyltransferase 1A (CPT1A), sterol regulatory element binding transcription factor 1c (SREBP-1c), and fatty acid synthase (FASN), early markers of metabolic impairment (P < 0.05). Moreover, CUN-BAE allowed identification of NW individuals with excessive body fatness, who were not yet presenting obesity-related molecular alterations. In these subjects, visceral fat correlated directly with circulating glucose, triglycerides, and total and LDL cholesterol, and with triglyceride-glucose and fatty liver indexes (P < 0.05). This is indicative of a metabolically obese NW phenotype.

Conclusions: Data obtained in our cohort of young normoglycemic volunteers support the use of the CUN-BAE index as a tool to estimate accurately body fat mass, but also as a first easy/effective screening tool to identify lean people with increased fat mass and increased metabolic risk.This trial was registered at clinicaltrials.gov as NCT04402697.

Keywords: BMI; CUN-BAE; metabolic risk; normal-weight obesity; visceral fat.