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

AIM: Obesity may start early in life. We investigated relationships between size and body composition variables in infancy and at four years 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 four years.

METHODS: 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 one week, 12 weeks and four years of age.

RESULTS: Positive associations between variables in infancy and at four years were found at one and 12 weeks for weight, height, BMI, fat-free mass and fat-free mass index (p≤0.002) and for fat mass, percent body fat and fat mass index (p≤0.04) at 12 weeks. Fat mass gained during infancy correlated positively (p≤0.031) with percent fat mass, fat mass index and BMI, all at four years. In girls, gains in fat-free mass during infancy correlated with BMI (p=0.0005) at four years.

CONCLUSION: 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. This article is protected by copyright. All rights reserved.