Family Affluence and Lifestyle Behaviors as Determinants of Fat Mass Index in University Students: A Sex-Specific Structural Equation Modeling Approach.

Physical activity was inversely associated with fat mass index in both males and females and represented the strongest protective factor in both sexes.

• Males: β = -0.36, 95% CI: -0.46 to -0.26, p < 0.001
• Females: β = -0.35, 95% CI: -0.45 to -0.25, p < 0.001
• The association was consistent in magnitude across sexes
• Sample included 199 males and 219 females (418 total university students)

The negative dietary index showed a significant positive association with fat mass index in both males and females.

• Males: β = 0.34, 95% CI: 0.21 to 0.48, p < 0.001
• Females: β = 0.26, 95% CI: 0.10 to 0.42, p = 0.001
• The association was stronger in males than in females
• Both positive and negative dietary indices were assessed using standardized questionnaires

Sedentary time was positively associated with fat mass index only in females, not in males.

• Females: β = 0.15, 95% CI: 0.02 to 0.28, p = 0.022
• No statistically significant association was observed in males
• This represents a sex-specific finding identified through sex-stratified structural equation modeling

Family affluence showed no statistically significant direct effect on fat mass index in either males or females.

• No significant direct effect was observed in males or females
• Family affluence was assessed using the Family Affluence Scale (FAS)
• This finding held despite family affluence being 'commonly considered an important contextual determinant of adiposity'
• The study design was cross-sectional, limiting causal inference

The structural equation models explained differing proportions of fat mass index variance between the sexes.

• The SEM model explained 30% of FMI variance in males
• The SEM model explained 37% of FMI variance in females
• Sex-specific models were estimated for males and females independently
• Variables included family affluence, physical activity, sedentary time, and positive and negative dietary indices