Association Between Macronutrient and Dietary Fiber Intake and Fat Mass Index Among Adults with Obesity

Abstract

Obesity has become a global public health challenge and is recognized as a complex chronic disease associated with numerous non-communicable diseases. Dietary factors, including macronutrient composition and dietary fiber intake, are considered important determinants of adiposity. However, evidence regarding their association with Fat Mass Index (FMI) in adults with obesity remains limited. This study aimed to determine the association between macronutrient intake, including energy, carbohydrate, protein, and fat intake, as well as dietary fiber intake, and Fat Mass Index among adults with obesity. A cross-sectional study was conducted between February and May 2026 among 100 adults with obesity. Dietary intake was assessed using non-consecutive 2-day dietary recalls. Body composition was measured using bioelectrical impedance analysis (BIA), and FMI was calculated as fat mass (kg) divided by height squared (m²). Spearman correlation analysis was used to evaluate unadjusted associations, while multiple linear regression analysis adjusted for age, sex, physical activity, and total energy intake was performed to examine independent associations with FMI. In unadjusted analyses, energy, carbohydrate, protein, fat, and dietary fiber intake were not significantly associated with BMI or FMI (all p > 0.05). However, after adjustment for age, sex, physical activity, and total energy intake, protein intake was positively associated with FMI (B = 0.053; 95% CI: 0.009–0.098; p = 0.020). Carbohydrate, fat, and dietary fiber intake were not significantly associated with FMI. Sex remained a significant predictor of FMI in all regression models (p < 0.001). Macronutrient and dietary fiber intake were not associated with BMI or FMI in the unadjusted analysis. After controlling for potential confounders, protein intake showed a positive association with FMI. These findings suggest that adiposity in adults with obesity is influenced by multiple factors beyond short-term nutrient intake.