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 4 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 4 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 1 week, 12 weeks and 4 years of age.

RESULTS

Positive associations between variables in infancy and at 4 years were found at 1 and 12 weeks 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 12 weeks. Fat mass gained during infancy correlated positively (p ≤ 0.031) with per cent fat mass, fat mass index and BMI, all at 4 years. In girls, gains in fat-free mass during infancy correlated with BMI (p = 0.0005) at 4 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.