Independent associations of body-size adjusted fat mass and fat-free mass with the metabolic syndrome in Chinese

Background: Excess fat leads to adverse health outcomes. Most previous studies investigating body fatness using BMI or fat percentage, which contain both fat mass and fat-free mass, were not able to differentiate the exposure. Aim: The present study assessed the independent association of fat and fat-free mass with metabolic syndrome (MetS) in Chinese. Subjects and methods: A population-based study of 1144 subjects aged 50–70 from urban and rural areas of Shanghai in 2005–2006 was employed. Body composition was measured with DEXA. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated. MetS was defined using the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria without waist circumference for its high correlation with body composition. Results: Both FMI and FFMI were significantly related with higher odds of MetS (OR 3.97, 95% CI 2.58–6.09 for FMI; OR 2.67, 95% CI 1.70–4.18 for FFMI, the highest quartile vs the lowest group) after adjusting for age, residence, sex, smoking, drinking, physical activity, medication, family history of chronic diseases, and fat-free mass (for FMI) or fat mass (for FFMI). Conclusion: Both FMI and FFMI are independently associated with increased MetS risks. Proper expression of body composition is essential in assessing body composition and disease risk association.