Limitations of BMI in Characterising Obesity Phenotypes

Introduction. BMI classifies obesity but does not account for body composition such as muscle or fat distribution. Matériels et méthodes. Participants with obesity undergoing metabolic surgery in Klang Valley were studied in a baseline analysis of a multicentre observational cohort. Bioelectrical Impedance Analysis (BIA) was used to measure visceral fat area (VFA), percentage body fat (PBF), and skeletal muscle mass (SMM). Sarcopenic obesity phenotype (SOP) was defined as obesity (BMI ≥ 27.5 kg/m²) plus low SMM (lowest quartile of sex-specific SMM index). Mann–Whitney U test compared continuous variables between SOP and non-SOP groups. Résultats. SOP participants had significantly lower body weight and BMI compared to non-SOP participants despite having obesity. There was no significant difference in percentage body fat, visceral fat area, or HbA1c levels between SOP and non-SOP groups, indicating comparable adiposity and glycaemic levels. Conclusion. Women with SOP have smaller body sizes but equivalent adiposity and glycaemic risks compared to non-SOP women. BMI alone is insufficient as a standalone indicator of obesity. Body composition analysis is essential to accurately identify metabolic risk in these individuals. Messages clés. SOP participants have significantly lower body weight and BMI despite obesity. Adiposity and glycaemic levels are comparable between SOP and non-SOP groups. BMI alone may mask important differences in body composition and metabolic risk.