Technical Abstract: Obesity results from energy imbalance. This study used data from the Bogalusa Heart Study to examine relationships between the dietary and physical activity behaviors of young adults. One thousand one hundred ninety-one young adults (76% Euro-American, 24% African-American, 61% female) completed a food frequency questionnaire and reported the location of meals consumed. Physical activity outside of work was assessed using a 5-item Likert scale. Analyses of covariance were used to determine if dietary consumption differed by physical activity level after controlling for ethnicity, BMI, age, and gender. Regression models were used to explore two- and three-way diet, gender, and ethnicity interactions. Consumption of fruit and dairy foods significantly differed (P < 0.05) by activity level with the most active group consuming 0.4 more servings per day for both fruit/fruit juices and dairy. Increased physical activity was significantly associated (P < 0.05) with decreased dietary fat. Increased physical activity was associated with increased consumption of fat among African-American males and decreased consumption of fat among Euro-American males. Euro-American females consumed less energy than the three other ethnic/gender groups. Increased consumption of fruit, dairy foods, and reduced energy from fat were related with increased physical activity with this relationship differing by gender and ethnicity.