The purpose of this pilot intervention was to examine whether changes in physical activity (PA) and sedentary behavior influence mood profile and dietary behavior. Three intervention (exercise, sedentary break, and control) groups were evaluated over a 4-week period. The exercise intervention consisted of progressively increasing vigorous intensity PA over a 4-week period among an inactive population. The sedentary break group was asked not to exercise, but instead, refrain from prolonged sitting (<45 minutes at a time). The control group was asked to remain inactive over the 4-week period. Compared to the exercise group and sedentary break groups, hostility levels increased in the control group over time. Also, improved dietary behaviors were observed in both the exercise and sedentary break groups. The sedentary break group, in particular, improved their dietary score consistently over time, whereas the exercise group improved mostly from baseline to midpoint. These results suggest that participating in vigorous activity and breaking up time spent in sedentary behaviors may potentially have an influence on mood profile and dietary behaviors.