BACKGROUND: One of the most popular expressions of massive group classes of aerobic physical activity is Zumba fitness. The aim of the study was to compare and relate the energy expenditure and the amount and intensity of physical effort during a Zumba fitness class in women with different Body Mass Index (BMI). METHODS: Body displacements of 61 adult women who performed a one-hour Zumba session were evaluated with triaxial accelerometers. In order to observe the effect of BMI women were divided into normal weight (N.=26), overweight (N.=21) and obese groups (N.=14). RESULTS: The average number of steps was 4533.3±1351 and the percentage of total class time of moderate to vigorous intensity (% MVPA) was 53.8±14.4%. The metabolic intensity average was 3.64±1.1 MET, with an energy expenditure by total body mass of 3.9±1.6 kcal/kg. When analyzing groups, the normal weight group had a greater number of steps (5184.2±1561.1 steps/class) compared to overweight (4244.8±1049.3 steps/class) and obese women (3756.9±685.7 steps/class) with P<0.05. Also, the normal weight group spent a lower percentage of class time at the lower levels of intensity (sedentary and lifestyle activity levels) and more time at the highest levels (vigorous and very vigorous) compared to obese women (P<0.05). Participants with a normal weight obtained a higher % MVPA (62.1±15%) compared to overweight (50.1±9.4%) and obese (44.1±11.9%) groups with P<0.05. A metabolic intensity of 4.6±1.9 MET in the normal weight group was higher compared to 3.5±1.0 MET in the overweight (P<0.05) and 3.1±1.2 MET in the obese group (P<0.05), was observed. The subjective perception of effort was 7.84±0.9 (Borg CR 10), no differences between groups. Also we observed in all participants that at higher BMI values, there were lower energy expenditure values per kilo of weight (r=-0.40; P<0.001), metabolic intensity (r=-0.39; P<0.001), step counts (r=-0.43; P<0.001) and % MVPA (r=-0.50; P<0.001). CONCLUSIONS: These results show that a higher BMI is associated with a lower intensity of effort, energy expenditure and amount of physical activity during a one-hour Zumba class, restricting to overweight and obese women to achieving the effort parameters recommended to control weight and improve cardiovascular fitness.