Body Composition Changes in Latino Population: Longitudinal Associations of Fat and Muscle Mass Indices

BMI has limitations in assessing metabolic health, especially in diverse populations. Fat mass index (FMI) and skeletal muscle mass (SMM) are more accurate predictors of obesity-related risks. Redefining obesity as a fat accumulation disease highlights the need for body composition-focused assessments in clinical practice.

This study assessed body composition changes in a Latino population over 6 months, evaluating the utility of fat mass index (FMI) and skeletal muscle mass (SMM) in detecting significant variations and exploring associations with baseline characteristics.

In this retrospective observational study, 1571 Latino patients were categorized into hypocaloric-high protein (HHP) and eucaloric-high protein (EHP) groups based on baseline BMI. Body composition was measured using bioelectrical impedance analysis at baseline and after 6 months. Chi-square tests evaluated categorical shifts in classifications, while multinomial logistic and linear regression models identified factors associated with fat and muscle mass changes, adjusting for sex, age, and baseline composition metrics.

Over 6 months, participants experienced significant reductions in body fat mass (31.24-27.25 kg, p < 0.001) and increases in skeletal muscle mass (24.31-25.85 kg, p < 0.001). In the HHP group, baseline FMI and age were significantly associated with fat mass changes, with younger individuals and those with lower baseline FMI being more prone to fat accumulation (p < 0.001). In both groups, higher baseline SMM was associated with greater likelihood of muscle loss and lower probability of muscle gain, suggesting a physiological ceiling effect (p < 0.001).

FMI and SMM enhance clinical assessments by providing more individualized metrics for obesity management in Latino populations. These findings support the integration of body composition analysis into clinical practice for more precise evaluation of metabolic health beyond traditional BMI classifications.