Obesity strengthens the associations between sarcopenia and both frailty and hospitalization, whereas reduces the risk of mortality

Abstract

Objectives: To assess the impact of different definitions of obesity on the association between sarcopenia and negative health outcomes in community-dwelling older adults.

Design: A longitudinal analysis using data from the Toledo Study of Healthy Ageing.

Setting: Community-dwelling older adults.

Participants: 1546 older adults (mean age 74.76 ± 5.75 years; 45.54% men).

Measurements: Sarcopenia was defined using population-standardized Foundation for the National Institutes of Health criteria. Obesity was assessed using several criteria previously proposed in the literature: Body Mass Index (BMI: >28, >30, >33 kg/m²), waist circumference (WC: >88♀; >102♂; and >98♀; >109♂), waist-to-hip ratio (WHR: >0.85♀; >0.90♂), fat mass percentage (%FM: >38%♀, >27%♂; >40%♀, >30%♂; and >43%♀, >31%♂), and population-based quartiles for trunk and appendicular fat mass. Frailty and disability were evaluated at baseline and 2.99 years later; hospitalization and mortality were tracked at 3.63 and 6.28 years, respectively. Regression models (logistic and Cox) and ROC analyses were conducted, adjusting for age, sex, comorbidities, and malnutrition.

Results: 350 participants (22.63%) met sarcopenia criteria. Obesity prevalence varied from 18.63% to 76.13%, depending on the definition. Obesity, regardless of the criterion, strengthened the associations between sarcopenia and frailty, while only some definitions (BMI and WC) strengthened the association with hospitalization; no impact was observed on disability. Sarcopenia was not significantly associated with mortality in the adjusted model, but the association became significant after adjustment for some obesity markers (WHR, truncal fat mass, and %FM). ROC curve analyses suggested that the capacity of sarcopenia to predict worsening frailty increased by 2% when obesity markers were included.

Conclusion: Obesity—particularly when defined by BMI and WC—strengthened the association between sarcopenia and adverse outcomes such as frailty and hospitalization. In contrast, higher fat mass was associated with lower mortality, suggesting a potential obesity paradox that warrants further research. These findings highlight the importance of assessing multiple obesity criteria alongside sarcopenia, while the potential protective role of obesity against mortality requires confirmation in further studies.