Birthplace, years of residence in the United States, and obesity among Mexican-American adults.

OBJECTIVE: To evaluate the association between birthplace (Mexico or U.S.) and obesity in men and women and to analyze the relationship between duration of U.S. residency and prevalence of obesity in Mexican immigrants.

RESEARCH METHODS AND PROCEDURES: We used cross-sectional data from 7503 adults of Mexican descent residing in Harris County, TX, to evaluate the relationships among BMI, birthplace, and years of residency in the U.S., controlling for demographic characteristics, physical activity level, and acculturation level.

RESULTS: U.S.-born adults had an increased risk (between 34% and 65%) of obesity compared with their Mexican-born counterparts. After controlling for recognized confounders and risk factors, this association was maintained in the highly acculturated only. Among highly acculturated obese U.S.-born men, 6% of the cases were attributable to the joint effect of birthplace and acculturation; in women, this proportion was 25%. Among Mexican-born women, there was an increasing trend in mean BMI with increasing duration of residency in the U.S.. Compared with immigrants who had lived in the U.S. for <5 years, Mexican-born women who had resided in the U.S. for >or=15 years had an adjusted BMI mean difference of 2.12 kg/m2 (95% confidence interval, 1.53-2.72).

DISCUSSION: Mexican-born men and women have a lower risk of obesity than their U.S.-born counterparts, but length of U.S. residency among immigrants, especially in women, is directly associated with risk of obesity. Development of culturally specific interventions to prevent obesity in recent immigrants may have an important public health effect in this population.