High protein intake along with paternal part-time employment is associated with higher body fat mass among girls from South China

Purpose Protein intake has been suggested to be associated with body composition among western children. Our aim was to determine whether protein intake is associated with body composition among Chinese children and to investigate whether parental socioeconomic status modifies these associations. Methods Cross-sectional data were collected from the baseline survey of an ongoing population-based prospective open cohort study conducted in 2013. In this survey, 2039 children in South China were recruited using cluster random sampling. Information of 1704 children (47% girls), aged 7-12 years from three primary schools (42 classes), on diet and anthropometry was included finally. Their daily protein intake was obtained by 3-day 24-h dietary recalls. Skinfold thickness, body height, and weight were measured to calculate percent body fat (%BF), fat mass index (FMI), and fat-free mass index (FFMI). Parental characteristics were collected by questionnaires. Results Among girls, protein intake was positively associated with %BF and FMI [estimate (SE) for %BF: 0.007 (0.003), p = 0.04; for FMI: 0.092 (0.002), p = 0.03], adjusted for pubertal stage, breast-feeding, maternal overweight, carbohydrate intake, energy intake, and physical activity level. Furthermore, there was interaction between paternal occupation and the relations of dietary protein with %BF and FMI (p (for interaction) <= 0.04). None of the associations between protein intake and %BF, FMI, or FFMI was found among boys. Conclusions Our data indicate that school-aged girls, but not boys, living in South China with higher dietary protein intake might have higher body fat mass, which could be modified by paternal occupation.