The incidence of childhood overweight is especially troubling among low income Latino youth. Grand Canyon Trekkers (GCT) was implemented as a quasi-experimental study in 10 Title 1 elementary schools with a large Latino population to examine the effects of a 16-week structured walking program on components of health-related physical fitness: Body Mass Index (BMI), waist circumference, and cardio-respiratory. Data on 1,074 research participants revealed no significance changes in BMI or waist circumference (p > .05); however, cardio-respiratory fitness increased by 37.1% over baseline. Cardiovascular fitness is an independent determinant of long-term health; therefore, the GCT program may have significantly improved the future health profile of the participants and decreased their risk of metabolic diseases. (Contains 3 tables and 2 figures.)