The focus of this study is the physical activity and nutrition behaviors of adolescents of Mexican origin. There are studies comparing physical activity and nutrition habits by ethnicity that report that Latinos and African Americans fare worse in terms of physical activity levels and healthy eating compared to Caucasian and Asian peers. A common predictor of health behaviors is socioeconomic status (SES). This study looks at various environments and how they influence or constrain the individual health choices adolescents make. For example, it reviews studies about foods available in the schools adolescents attend and neighborhoods in which they live. After reviewing the literature, it was clear that more studies with ethnically homogeneous samples are needed to find subtle differences in health behaviors that go beyond SES. Chapters 3 and 4 are based on a sample of adolescents from Mexican descent from the National Longitudinal Study of Adolescent Health. Chapter 3 is about the adolescents’ physical activity behaviors while chapter 4 is about their nutrition behaviors. Both studies analyze the influence of acculturation on these health behaviors. These studies analyze whether findings differ for males and females. Both studies include SES, parent’s marital status, and frequency of hanging out with friends as control variables.