Background Physical activity and dietary prescription are the mainstay of overweight and obesity management. Aim To compare the effects of physical activity or dietary management in overweight or obese sedentary women. Material and Methods Thirty-four physically inactive adult women with overweight or obesity, were intentionally divided into three groups: controls (C), exercise (E) and dietary prescription (DP). Women in the E group were trained in a circuit for twelve weeks and a hypocaloric diet was prescribed to those in the DP group. Blood pressure, body composition and phase angle (FA) measured using bioimpedance and dynamometry, were measured at baseline and the end of the intervention. Results Women in the E group had a significant increase in muscle mass and intracellular water and significant decreases in systolic and diastolic blood pressure levels. No significant differences in dynamometry were observed between groups. The DP group had significant decreases in body weight, fat mass, body mass index, waist circumference, systolic and diastolic blood pressure. Conclusions The DP group had a higher weight reduction than the E group. Dietary prescription should be complemented with a physical activity program in the management of overweight or obesity.