Identification of Sarcopenic Obesity by Fat-to-Muscle Ratio in Older Adults: A Cohort Study.

FMR showed the strongest independent association with sarcopenic obesity among all screening tools evaluated in both sexes.

• In females, FMR per 1-SD OR = 3.06 (95% CI = 2.53–3.71); in males, OR = 3.09 (95% CI = 2.67–3.58)
• BMI was the second strongest in females (OR = 2.85, 95% CI = 2.35–3.58) but much weaker in males (OR = 1.43, 95% CI = 1.26–1.62)
• WC had lower ORs: female OR = 2.26 (95% CI = 1.86–2.74); male OR = 1.24 (95% CI = 1.08–1.41)
• PhA was not independently associated with sarcopenic obesity in females (OR = 1.12, 95% CI = 0.93–1.34) and was inversely associated in males (OR = 0.65, 95% CI = 0.56–0.76)
• Associations were determined by logistic regression analysis with adjustment for covariates, treating screening tools as continuous variables

FMR had the highest AUC for sarcopenic obesity screening in both males and females compared to other tools.

• FMR AUC: female = 0.82 (95% CI = 0.79–0.85); male = 0.81 (95% CI = 0.79–0.84)
• BMI AUC: female = 0.76 (95% CI = 0.72–0.79); male = 0.55 (95% CI = 0.51–0.59)
• WC AUC: female = 0.70 (95% CI = 0.66–0.75); male = 0.53 (95% CI = 0.49–0.57)
• PhA AUC: female = 0.63 (95% CI = 0.58–0.69); male = 0.70 (95% CI = 0.67–0.74)
• ROC analysis described predictive ability as 'moderate' for all tools

The study included 7916 community-dwelling older adults diagnosed with sarcopenic obesity using JWGSO criteria.

• Mean age was 73.5 ± 6.2 years; 54.8% were female
• Data were drawn from the National Center for Geriatrics and Gerontology Study of Geriatric Syndromes (NCGG-SGS), a national cohort study conducted in Japan
• Sarcopenic obesity was diagnosed by the Japanese Working Group on Sarcopenic Obesity (JWGSO) criteria
• FMR and phase angle (PhA) were measured using bioelectrical impedance analysis (BIA)
• This was a cross-sectional analysis of a cohort study

BMI and WC performed substantially worse than FMR for identifying sarcopenic obesity in males.

• BMI AUC in males was 0.55 (95% CI = 0.51–0.59), compared to FMR AUC of 0.81 (95% CI = 0.79–0.84)
• WC AUC in males was 0.53 (95% CI = 0.49–0.57), indicating near-chance diagnostic performance
• In females, the gap between FMR and BMI was smaller (AUC 0.82 vs. 0.76), but FMR remained superior
• The sex difference in BMI and WC performance suggests these anthropometric tools are less applicable to males for sarcopenic obesity screening

Phase angle (PhA) showed inconsistent and generally weaker diagnostic performance for sarcopenic obesity compared to FMR.

• PhA AUC was 0.63 in females (95% CI = 0.58–0.69) and 0.70 in males (95% CI = 0.67–0.74)
• PhA was not independently associated with sarcopenic obesity in females after covariate adjustment (OR = 1.12, 95% CI = 0.93–1.34)
• In males, PhA was inversely associated with sarcopenic obesity (OR = 0.65, 95% CI = 0.56–0.76), reflecting its role as a muscle quality marker rather than an obesity indicator
• PhA showed higher AUC in males than females, opposite to the pattern seen with FMR, BMI, and WC