Book excerpt: The prevalence of obesity in Mexican-American children is higher than in non-Hispanic white children. Binational studies conducted in US immigrant and Mexican communities can provide a unique perspective on factors that may be related to childhood obesity. This dissertation presents the findings from a cross-sectional, binational study, conducted from April to December 2006. The sample included families with children ages one to six years, living in immigrant households in Ventura County, California (US) with a similar cohort of children, living in the municipality of Cueramaro, Guanajuato (MX), where out-migration is common. The interview included items to collect data on demographic characteristics; household food security; infant and child feeding practices; maternal perception of the child's diet and weight; a 30-item food frequency questionnaire (FFQ); and a 24-hour dietary recall (DR). Also weight and height (or length for younger children) was measured on all children one to six years living in the household to calculate the body mass index-for-age z-scores (BMIZ) and the height-for-age z-scores (HAZ), indicators of body fatness and linear growth, respectively. The final sample includes 95 families in US and 200 families in MX. The present work includes four chapters. The first is a literature review that examines biological, family and community-level factors contributing to the development of childhood overweight and obesity among Mexican-American populations. The second chapter compares maternal perceptions and concerns; infant and child feeding practices; and growth status among US and MX populations. The third chapter identifies differences in child feeding strategies and dietary intakes across populations and also examines associations between feeding strategies and dietary intakes. The final chapter examines potential mechanisms through which country of residence is associated with childhood overweight among families in MX and US. Specifically, the study examines evidence for the hypothesis that food security mediates the relationship between country of residence and childhood obesity. Results of the analyses provide evidence that the prevalence of low and very low food security is significantly higher in the MX than in the US sample. Overweight and obesity is significantly higher among the US children compared to their counterparts in MX. There are also differences in child eating patterns and maternal concerns about their child's weight among countries. Based on the FFQ, children in the US, compared to children in MX, consume more pizza, hot dogs, hamburgers, instant noodles, ready-to-eat cereal, and American cheese and less fried beans, corn tortillas, and rice. However children in MX, compared with children in US, consume soda more often. Based on the 24-DR, there are few differences in most of the macro or micronutrient intakes. In examining the relationship between feeding strategies and nutrients intakes; children who ask for food/beverages or take food from the refrigerator or pantry between meals, have significantly higher intakes of total and animal protein. Children, whose mothers use food or beverages to calm his or her child, have significantly higher intakes of saturated fatty acids. Food security status is significantly related to BMIZ using different scales for food security. In the regression models to evaluate the mediation effect of food security on the country and BMIZ, food security does not remain significant in the models. However, after adjusting for household size and maternal education, about 15% of the relationship between country and BMIZ is explained by food insecurity, a Mexican dietary pattern, and maternal feeding strategies.