Visceral Adiposity as a Key Modifier of BMI ‐Adjusted Calf Circumference in Older Asian Men

We read with great interest the article by Miyahara et al., “Association of BMI-Adjusted Calf Circumference and Age-Specific Cutoff Values With In-Hospital Falls Among Older Adults” 1. The authors convincingly demonstrated that BMI-adjusted calf circumference (CC) serves as a valuable predictor of in-hospital falls in older women. However, the absence of a significant association in the male cohort raises an important physiological question that merits further consideration. We commend the authors for utilizing the Japan Hospital Acquired Complications (J-HAC) database to advance sarcopenia screening. Building on their discussion regarding the limitations of Body Mass Index (BMI) adjustments, we propose that the distinct “thin-fat” phenotype of the older Japanese population—specifically the sexual dimorphism in visceral adiposity—may explain the observed discrepancies. The study employed adjustment factors derived from the US National Health and Nutrition Examination Survey (NHANES) 2. While standardized, these factors may not accurately reflect the adiposity profiles of octogenarian Japanese men. It is well-established that Japanese individuals exhibit greater visceral adipose tissue (VAT) accumulation for a given BMI compared to Caucasians 3. Crucially, the trajectory of fat redistribution during aging differs significantly by sex. While Japanese women tend to retain subcutaneous adipose tissue (SAT) into advanced age, Japanese men experience a marked preferential accumulation of visceral fat coupled with a reduction in subcutaneous depots 4. This physiological divergence suggests that BMI may function differently as a confounding variable in men and women. In older Japanese men, a stable or elevated BMI is often driven by visceral adiposity, while the subcutaneous fat layer on the calf thins. Consequently, adjusting CC based on BMI—which assumes a linear relationship between total body mass and peripheral subcutaneous fat—may introduce statistical noise for male patients. In this demographic, a “high BMI” likely reflects central obesity rather than the leg adiposity the equation intends to correct. This may have obscured the relationship between true muscle mass and fall risk in the male cohort. To bridge this gap, future research should integrate markers of central obesity that are less influenced by overall body mass. The Weight-adjusted Waist Index (WWI), calculated as waist circumference divided by the square root of weight, has recently emerged as a superior predictor of sarcopenia and disability compared to BMI 5. Unlike BMI, WWI isolates central adiposity, offering a more precise proxy for the visceral fat burden that characterizes the high-risk “sarcopenic obese” Japanese male. We suggest that future analyses of the J-HAC cohort could benefit from evaluating whether WWI, or a similar “Visceral-to-Subcutaneous” proxy, serves as a more robust adjustment variable than BMI for the male population. Such refinements may help improve the sensitivity of bedside screening tools and enhance fall risk stratification in older men. The authors have nothing to report. The authors have nothing to report. The authors have nothing to report. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.