Rethinking Obesity Classification: Population-Level Insights from a Small Island States

Abstract Background Traditional measures such as BMI are commonly used to define obesity, but they may not capture the complexity of obesity-related risk. This study applied newly proposed definitions of pre-obesity and clinical obesity by the Lancet Diabetes & Endocrinology Commission and compared them with standard anthropometric measures in Malta-a population with a high prevalence of obesity. Methods A nationally representative, cross-sectional health examination survey was conducted in Malta between 2014 and 2016 (weighted N = 3,947). Anthropometric, sociodemographic, behavioural, and biochemical data were collected. Obesity was assessed using BMI, waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WtHR), and the newly proposed definitions. Metabolic syndrome (MetS) was used as a clinical complication. Binary logistic regression models were used to examine associations with MetS, adjusting for age, sex, education, and locality. Results Obesity prevalence varied by classification: 34.08% (BMI), 34.81% (WC), 68.94% (WHR), 39.17% (WtHR), and 22.40% (clinical obesity). All anthropometric measures showed significant associations with MetS, even after adjustment. Obesity defined by BMI had the strongest association (OR: 18.84, 95% CI: 14.13-25.13), while the newly defined clinical obesity also showed a strong association (OR: 9.89, 95% CI: 8.37-11.67). The pre-obesity category was negatively associated with MetS (OR: 0.16, 95% CI: 0.12-0.22), supporting its distinction as a preclinical state. Conclusions Different anthropometric measures identify different subgroups within the population, yet all are significantly associated with MetS. The findings support the utility of the Lancet Commission's refined definitions, particularly the pre-obesity classification, in guiding early intervention strategies. Key messages • Applying multiple anthropometric measures reveals variation in obesity classification, but all remain significantly associated with metabolic complications, highlighting their clinical value. • The newly defined pre-obesity category shows a protective association with metabolic syndrome, supporting its use as a meaningful stage for early risk identification and intervention.