Association between a common variant near MC4R and change in body mass index develops by two weeks of age

The common polymorphism rs17782313 lying 188 kb downstream of the MC4R gene has recently been found to be unequivocally associated with body mass index (BMI) and obesity risk in adults and children. Our objective was to test the association between rs17782313 and neonatal weight gain in a contemporary population.

This was a cross-sectional, hospital-based study using 278 healthy Caucasian newborns [142 girls; gestational age (mean +/- SD) 39.3 +/- 1.4 weeks, birth weight 3.1 +/- 0.6 kg]. Body composition was assessed by dual-energy X-ray absorptiometry (DXA) at approximately 13 days (range 9-20) and rs17782313 was genotyped by restriction fragment length polymorphism analysis.

rs17782313 was not associated with weight, length or ponderal index at birth. However, it was associated with changes in BMI (p = 0.0004) over the first 2 weeks of life and with body weight (p = 0.02) and BMI (p = 0.007) at age 2 weeks. Despite this, DXA measures of fat and lean mass failed to show any simple associations.

Similar to other genetic variants associated with childhood and adult obesity, the association between rs17782313 genotype and body weight develops rapidly during the first 2 weeks of life, once caloric intake is regulated by the infant's appetite.