Early Life Determinants of Overweight and Obesity in a Sample of Mexico City Preschoolers

Introduction: Childhood obesity is a growing public health problem with long-term consequences. Understanding the early contributing factors is crucial for prevention and early intervention. This study explored the influence of breastfeeding, birth weight, gestational age, parental education, and sex on body mass index (BMI) during infancy. Methods: Standardized weight and height measurements of children followed a common World Health Organization protocol. Information on sex, gestational age, birth weight, breastfeeding practices and duration, family income, and mother’s educational level, as well as other sociodemographic factors, was collected from clinical records. Linear regression models were calculated. Results: This study analyzed factors associated with overweight and obesity in 286 children under 5 years of age, using data from daycare records. Several significant associations were found. Regarding breastfeeding, while 85% of children received breast milk, only 23% did so exclusively for at least six months. Although no significant difference was observed in BMI change between exclusive and partial breastfeeding groups between birth and 5 years of age, the duration of exclusive breastfeeding, the birth BMI, and the educational level predicted 54% of the variability in BMI percentile change from birth to two years (p = 0.001). In addition, girls showed significantly longer exclusive breastfeeding. Regarding gestational age, preterm infants showed a significantly greater increase in BMI percentile compared to term infants. Gestational age also proved to be a significant factor in explaining BMI variability up to 5 years of age. Regarding sex, at age 5, boys showed a significantly higher prevalence of overweight and obesity than girls. With respect to family income, no statistically significant difference was found in BMI change between birth and 2 years of age; however, this variable warrants further investigation in future studies with greater statistical power. Finally, birth BMI was a significant predictor of BMI variability at 5 years of age. Conclusions: In this study, gestational age, sex, birth BMI, and the duration of exclusive breastfeeding were the most important determinants of BMI and the prevalence of overweight and obesity in children up to 5 years of age. Further studies are needed to thoroughly explore the role of family income and other factors.