Carbohydrate-to-fat ratio is positively associated with comprehensive frailty across protein-intake levels in older adults

Abstract Purpose Diet influences frailty, and protein intake has been a prime focus of prevention. However, frailty remains prevalent, even among older adults with relatively high protein intake, suggesting the influence of remaining energy distribution between carbohydrates and fats. We investigated the association between the carbohydrate-to-fat energy ratio (CFr) and comprehensive frailty in older Japanese adults and whether this association differed by protein intake. Methods Cross-sectional baseline data from 5679 community-dwelling adults aged ≥ 65 years in the Kyoto–Kameoka Study were analyzed. Diet was assessed using a validated 46-item food-frequency questionnaire. Percent energy from carbohydrates, fats, and protein was calculated. CFr was defined as the ratio of percent energy from carbohydrates to that from fat. Frailty was defined as a Kihon Checklist score ≥ 7. Multivariable logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) for frailty across CFr quartiles, adjusting for sociodemographic, lifestyle, and health-related factors. Restricted cubic splines assessed dose–response associations overall and within sex-specific tertiles of protein intake. Results Among the 5679 participants, 1705 (30.0%) had comprehensive frailty. Compared with the lowest CFr quartile, the adjusted ORs were 1.12 (95% CI, 0.92–1.36) for Q2, 1.44 (1.18–1.76) for Q3, and 1.92 (1.55–2.38) for Q4 ( P for trend < 0.001). Positive associations were also observed across sex-specific protein-intake tertiles, with no evidence of effect modification by protein intake. Conclusion A higher CFr is associated with a higher prevalence of comprehensive frailty in older Japanese adults, with broadly similar associations across protein-intake levels.