Metabolic Health–Adiposity Phenotypes Among Adults in Myanmar: Exploratory Implications for Primary Care Screening Beyond Body Mass Index

Introduction Metabolic abnormalities may occur in adults whose body mass index (BMI) is below the conventional overweight threshold, potentially leaving cardiometabolic risk unrecognized in primary care. This study aimed to describe metabolic health–adiposity phenotypes and examine their correlates among adults in Myanmar. Methods This secondary cross-sectional analysis included 302 adults from a community survey in Yangon. Participants were classified as metabolically healthy non-overweight (MH-NOW), metabolically unhealthy non-overweight (MU-NOW), metabolically healthy overweight/obese (MH-OW/O), or metabolically unhealthy overweight/obese (MU-OW/O). Multinomial logistic regression estimated adjusted relative risk ratios (aRRRs) with 2,000-repetition bootstrap confidence intervals (CIs). Results MH-NOW accounted for 33.4% of participants, MU-NOW 14.9%, MH-OW/O 19.2%, and MU-OW/O 32.5%. Among 146 participants with BMI <25 kg/m², 45 (30.8%) were metabolically unhealthy. Compared with MH-NOW, MU-NOW participants were older and had greater waist circumference, whereas mean BMI differed little. BMI alone showed limited discrimination between MH-NOW and MU-NOW (AUC 0.550), compared with waist circumference (AUC 0.668). Each 10-year increase in age was associated with higher relative risks of MU-NOW (aRRR 1.62, 95% bootstrap CI 1.24–2.24) and MU-OW/O (aRRR 1.35, 95% bootstrap CI 1.09–1.74). In exploratory classification analyses, BMI ≥25 kg/m² had 68.5% sensitivity and 63.5% specificity; combining BMI ≥25 kg/m² with central adiposity increased sensitivity to 74.8% but reduced specificity to 59.1%. Conclusions Metabolic unhealthiness was present across BMI categories, including among participants without overweight. These findings support further evaluation of risk-assessment approaches incorporating age and waist circumference alongside BMI, while external validation is required before clinical implementation.