Associations of anthropometric-related phenotypes with functional and clinical outcomes in community-dwelling older adults: a cross-sectional analysis of ELSI-Brazil

Obesity remains a major public health concern, particularly among older adults. These concerns are further amplified by the challenges associated with its diagnosis. In this context, anthropometry remains the most practical and widely used method to “identify” obesity. In population-based studies, body mass index (BMI) is commonly accepted; however, its use remains debatable, especially in older populations. In contrast, waist circumference (WC) is more strongly associated with visceral adiposity and, consequently, with greater health repercussions than BMI alone. As this field continues to evolve, studies combining these parameters (i.e., different BMI classifications alongside WC) remain scarce. Therefore, this study aimed to evaluate the associations of different anthropometric parameters with functional and clinical outcomes in a population-based sample of Brazilian older adults. This cross-sectional study used data from 5,380 community-dwelling older adults (aged ≥ 60 years) from ELSI-Brazil (2019–2021). Anthropometric phenotypes were classified using BMI and WC. Functional outcomes included basic and instrumental activities of daily living, while clinical outcomes consisted of frailty, falls, fractures, and hospitalizations. The underweight phenotype was associated with higher odds of frailty ( adjusted OR = 2.0; 95% CI: 1.2–3.3) and prolonged hospitalization ( adjusted OR = 4.1; 95% CI: 1.2–13.4). The combination of underweight by BMI with abdominal obesity (by WC) showed a borderline significant association with functional disability ( adjusted OR = 3.1; 95% CI: 1.0–10.2). Overweight by BMI was inversely associated with frailty ( adjusted OR = 0.7; 95% CI: 0.5–1.0). Obesity, combining BMI ≥ 30 kg/m 2 and high WC, was associated with a higher risk of falls (OR = 1.3; 95% CI: 1.1–1.6) and functional impairment in the unadjusted models. Our study suggests the clinical relevance of combining anthropometric markers of obesity in community-dwelling older adults. We provide initial evidence that the coexistence of low BMI and high WC, although rare, is suggestive of potential clinical implications due to its association with higher odds of functional impairment. Additionally, both underweight and obesity may offer added clinical value beyond single measures.