Body Composition within the First 3 Months: Optimized Correction for Length and Correlation with BMI at 2 Years

Area of Science:

• Pediatric growth and development
• Infant body composition analysis
• Public health and nutrition

Background:

• Limited reference data exists for infant body composition, impacting assessments of early growth.
• Early infant growth is linked to long-term health outcomes.
• Accurate body composition measures in infancy are needed.

Purpose of the Study:

• To establish reference data for infant fat mass (FM) and fat-free mass (FFM) adjusted for length (L) within the first three months.
• To determine if these infant body composition measures predict body mass index (BMI) at two years of age.

Main Methods:

• Air displacement plethysmography was used to measure body composition in term infants at birth and around two months.
• Age- and sex-specific reference data were generated for FM, FFM, FM/L³, and FFM/L².
• These infant measures were compared with BMI at two years.

Main Results:

• FM/L³ and FFM/L² were identified as optimal length-independent indices for body composition.
• During the first three months, FM/L³ increased significantly in both males and females.
• FFM/L² remained relatively stable in males and females during the same period.
• Higher FM and weight Z-scores at two months were associated with increased odds of a BMI Z-score ≥2 at two years.

Conclusions:

• FM/L³ and FFM/L² offer reliable, length-independent assessments of infant fat mass and fat-free mass.
• Infant fat mass increases in the first three months, while fat-free mass remains stable.
• Weight Z-score at two months is a comparable predictor of two-year BMI as infant body composition parameters.