Fat and fat-free mass of healthy Swedish children show tracking during early life, but there are differences.

Abstract

Obesity may start early in life. We investigated relationships between size and body composition variables in infancy and at 4years of age using valid estimates of body composition. The results were compared to those obtained when body mass index (BMI) was used to estimate body fatness at 4years. Using air displacement plethysmography, size, fat mass and fat-free mass were studied, between 2007 and 2015, in 253 full-term healthy Swedish children at 1week, 12weeks and 4years of age. Positive associations between variables in infancy and at 4years were found at 1 and 12weeks for weight, height, BMI, fat-free mass and fat-free mass index (p≤0.002) and for fat mass, per cent body fat and fat mass index (p≤0.04) at 12weeks. Fat mass gained during infancy correlated positively (p≤0.031) with per cent fat mass, fat mass index and BMI, all at 4years. In girls, gains in fat-free mass during infancy correlated with BMI (p=0.0005) at 4years. The results provide information regarding body composition trajectories during early life and demonstrate limitations of BMI as a proxy for body fatness when relating early weight gain to variables, relevant for later obesity risk.