Date of Award


Degree Name

MS in Agriculture - Food Science and Nutrition


Food Science and Nutrition


Lisa Nicholson


OBJECTIVE. The impact of exclusively breastfeeding (EBF) on child body mass index (BMI) from birth through 60 months of age was investigated.

METHODS. 60,190 mothers and children attending Women, Infant and Children (WIC) clinics in the Santa Barbara and San Luis Obispo counties of California provided data on breastfeeding duration, maternal pre-pregnancy BMI, and child weight-for-length (WL) was measured at 3 month intervals until 5 years of age. Missing time points were interpolated in determining child BMI/WL z-score trajectories plotted on the Center of Disease Control (CDC) infant and child growth curves. Multivariate analysis of variance was used to contrast the impact of notbeing EBF against being EBF from 0-3 months, and being EBF from 0-6 months. In subsets of the population the relationship was examined in White Hispanic (n=43,360) versus all others race/ethnicities of (n=16,830) children. All models controlled for maternal pre-pregnancy maternal BMI and income.

RESULTS. Duration ofEBF from 0-3 months and 0-6 months of age was protective against child BMI z-scores being above the average growth trajectory (P=0.0001). Asignificant inverse association between EBF and overall BMI/WL z-scores for both males and females (P<0.0001) was found. The impact of EBF on child growth trajectory began to weaken at 15 months for females and 18 months for males. Children who were not EBF had higher mean BMI/WL z-scores at every time point than those who were EBF. Those who were EBF for 0-3 months had a lower BMI; those who were EBF for 0-6months had even lower BMI/WL z-scores by 5 years of age. Hispanic children had a higher BMI growth curve than non-Hispanic children even after adjusting for EBF, pre-pregnancy BMI, and income. Mothers with a higher pre-pregnancy BMI tended to have children with higher BMI/WL z-scores (P<0.0001).

CONCLUSION. This study supports the public health efforts to encourage EBF for at least 3 months and optimally for 6 months as a method to protect against childhood obesity.