The effectiveness of an 8-week Zumba programme for weight reduction in a group of Maltese overweight and obese women
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- Micallef, C. Sport Sci Health (2014) 10: 211. doi:10.1007/s11332-014-0195-8
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Zumba dance exercises are promoted for body weight reduction. However, scientific research on its potential as a weight loss tool is scant. Only a few energy expenditure studies on small samples of relatively young and apparently healthy volunteers were performed, and the energy cost of Zumba has not been translated into actual weight reduction. The study investigated the before–after effects of a Zumba programme on the weight and body mass index (BMI) of 36 females, mean age 34.25 ± 8.50 years and mean BMI 32.98 ± 5.32 kg/m2.
The intervention involved 16 hourly Zumba sessions held twice weekly over 8 weeks. The exercises comprised a mixture of merengue, salsa, reggaeton and bachata with warm-up and cool-down activities. They were of low-impact style, but were maintained at vigorous intensity that was still bearable for the obese subjects. An important requirement was that the programme had to be taken as an additional part of their lives and not as a means of altering their nutrition and physical activity habits.
The subjects had statistically significant decreases and large effects for weight and BMI: 2.13 kg, t(35) = 13.77, P < 0.0005, d = 2.30, and 0.83 kg/m2, t(35) = 13.02, P < 0.0005, d = 2.17, respectively.
Good programme adherence and other strengths were attributed to this study. However, there could have been factors like history threats that affected the changes. Further studies are therefore required to establish the effectiveness of Zumba as an exercise modality for weight loss.
KeywordsBody mass index Body weight Obesity Overweight Weight loss Zumba
Physical activity (PA) normally increases energy expenditure (EE) and this contribution to negative energy balance can lead to body weight loss .
Zumba® Fitness (or Zumba) is being promoted by fitness industries as an intensive cardiovascular exercise to help people loose excess weight [2, 3]. Founded in 2001, it is estimated that these Latin-inspired aerobic exercises with music are performed by 14 million people in over 150 countries . However, as admitted by Luettgen, Foster, Doberstein, Mikat, and Porcari , despite its widespread popularity, scientific research documenting the potential health benefits of this dance form of exercises is scant.
The five identified Zumba studies involving relatively young and apparently healthy volunteers with brief notes on sample characteristics and methods of estimating energy expenditures
The variance in EE probably depended on the different dance styles performed. Moreover, the methodologies were not consistent throughout the studies. For example, heart rate telemetry and open circuit spirometry combined together could have more encumbered the subjects’ movements, thus lowering their EE, than when using only heart rate monitors and accelerometers on their own. Another drawback of these studies was that they could not appeal to a broad spectrum of the population as they lacked middle-aged, overweight and obese participants.
Descriptive characteristics of the 36 participants who completed the whole 8-week Zumba programme
Mean ± s
34.25 ± 8.50
Initial weight (kg)
85.98 ± 16.28
Mean height (cm)
161.20 ± 6.46
Initial BMI (kg/m2)
32.98 ± 5.32
The null hypothesis (H0) that followed was: an 8-week Zumba programme consisting of twice weekly hourly sessions did not have any statistically significant effects on the weight and BMI of a group of overweight and obese female participants. The study therefore aimed to disprove the H0 and formulate an alternative hypothesis (H1): that the programme had significant effects on the participants’ weight and BMI.
Description of the intervention
The intervention involved a free structured Zumba programme consisting of 16 h of supervised exercise sessions held twice weekly over eight consecutive weeks. The exercises consisted of a mixture of commonly used dance rhythms in roughly equal proportions: merengue, salsa, reggaeton and bachata. The programme was carried out in a large hall adapted for exercise-to-music classes.
Each 1 h session included 5–10 min of warm-up and another 5–10 min of cool-down and stretching activities. Resting periods were very brief so that the subjects were exposed to not less than 75 min of weekly vigorous aerobics (real Zumba) as the volume normally recommended for substantial health benefits . Participants also had at least two recovery days between training sessions.
It was understood that jumping was not appealing to obese participants. This meant that the style had to be maintained at low impact. Consequently, due to the requirement for weight loss, the intensity had to be kept high. A certified Zumba instructress performed talk tests regularly to control the intensity levels within the vigorous range, thus ensuring that subjects were not exposed to strenuous efforts that they were unable to cope with.
There were no sponsors; the investigator funded all the expenses in connection with the services provided by the instructress.
Study design and justifications
The study employed a pre-test post-test single-group design. If the effectiveness of Zumba on body composition had to be examined using a double group design, the subjects in the comparison group would probably know what the programme group was getting and develop a competitive attitude with them by, for example, doing Zumba at home. Apart from compensatory rivalry, there was also a good reason to suspect that a control group would lose interest by not cooperating with the research’s requirements or simply drop off if they saw others benefiting from or enjoying a free programme.
Moreover, as obesity is actually a disease and exercise can be regarded as an alternative therapy, and this 8-week programme was the first known attempt of therapeutic intervention with Zumba for the control of obesity, it was appropriate to use a single-group design because uncontrolled studies played an integral part in the early evaluation of novel therapies .
Furthermore, as each subject was exposed to repeated tests, the strength of such within-subjects analysis laid on the fact that subjects were acting as their own controls thus eliminating between-subjects variability .
Criteria and requirements for participating
A non-proportional quota sample was recruited on a voluntary basis. Subjects were all females. As aerobic dance has been mostly frequented by women , and in Britain 98 % of Zumba practitioners were females , a study involving males in addition to females could have resulted in difficulty recruiting males and substantial male dropouts.
As the study addressed the problem of excess body weight, by the World Health Organization definition of the BMI cut-off points , subjects had to be at least overweight with BMI >24.99 kg/m2.
The lower age limit was 18 years. This was in accordance with the legal definition of entering adulthood. Beyond 50 years, women were not eligible to participate in vigorous activity as they were considered at risk of cardiovascular events if they were previously inactive .
Participants had to maintain their usual ad libitum diets and to avoid extra or less PAs than their normal routines during the 8-week study period. Compliance with these measures was important to ensure as much as possible that the internal validity was not threatened by confounders such as dieting or by other activities besides Zumba.
Although participants had to be below 50 years, their unhealthy weights, especially if coupled with sedentariness, meant that they still fell under the moderate risk category . Subjects therefore had to obtain medical clearance by their physician before starting the programme.
A priori calculations for sample size
By using data from a similar 8-week aerobic study conducted by Gezer and Çakmakçi , the pooled s for BMI was found to be 2.145 kg/m2. After calculating the standardized difference between the two means, the effect size, d was, through Cohen’s classification, found to be of a medium effect (0.5) .
A table for determining n in relation to paired t tests  was used. After setting the power at 0.8 and taking d as 0.5, the sample for the Zumba intervention was found to require 34 individuals. However, n was increased by 20 % to accommodate the expected dropouts as advised by Hudson , making n targeted for 41 females.
Recruitment of subjects
Participants were recruited through a call on a radio programme and a newspaper advert. The first 41 applicants that met all the recruitment requirements and needed the programme were accepted on a first-come-first-served basis. Referred to as truncated sampling, the number of people not selected was not recorded because the recruitment process had explicitly announced the requirements including the desired n .
Ethical issues and risk assessments
All procedures were in accordance with the Helsinki Declaration of 1975, as revised in 2000. The research was first approved by the Ethics Panel of Staffordshire University and later by the Research Ethics Committee of Malta. Information about the study was explained orally and in writing and the volunteers then gave their written informed consent.
Foreseeable risks that were assessed included: (1) ligament tears, (2) overcrowding, (3) dehydration and (4) cardiac events. The respective main control measures were, for: (1) warming-up, wearing Zumba shoes, availability of a pain relief spray, and low-impact exercising; (2) allowing at least 1.5 m2 per participant; (3) availability of a free water dispenser; (4) presentation of medical clearance certificates, not permitting over 50-year-olds to participate, and performing talk tests.
Anthropometric measurements and other data collection
The three main variables were body weight, height and BMI. Two data collections occurred before and after the 8-week programme, and the sessions were always held at the same time in the evening. The participants had to remove as much outer wear as possible including their shoes. Their age and number of sessions attended were also recorded.
Body weight was measured with a Seca 807 digital scale, which was accurate to 0.1 kg. As a standard procedure, the accuracy of the scale was checked at the beginning of the weighing session with a weight of 5 kg and the readings had to be not >0.2 kg higher or lower than the standard weight.
The subjects’ heights were measured to the nearest 0.1 cm with their heads aligned in the Frankfort horizontal plane using a portable Seca 213 stadiometer. Although height measurements along an 8-week period were supposed to be constant, heights were taken before and after the intervention, with the difference between each two measurements not exceeding 2 cm. Eventually, the average between each two acceptable measurements was used for the BMI calculations.
Calculated as weight divided by height squared, BMI is a non-invasive and yet validated anthropometric measurement for assessing the weight index in relation to height .
Statistical analyses were performed using Statistical Package for Social Sciences (SPSS) version 17. The level of statistical significance was set at P < 0.05 and two-tailed hypothesis were applied.
After the data were screened by testing the assumptions of normality and no outliers, two paired t tests were run to determine the t statistic (t), and other relevant information for weight and BMI. Cohen’s d was also calculated and the results were compared with Cohen’s classification of effect size .
Description of the attendance for the initial group of participants
Of the 41 females that were selected during the recruitment phase, 36 completed the whole 8-week intervention, meaning that there were five dropouts. On inspection of the attendance sheets, observations showed that they dropped out after their first, second, fourth (two subjects), and sixth sessions, thus indicating that they were early dropouts.
Maximum exercise compliance with respect to full attendance over the whole intervention was achieved by 32 subjects or 78.05 % of the participants, whereas good programme adherence in terms of all those who completed the programme (n = 36) was acquired by 87.80 %, implying a dropout rate of 12.20 %.
Frequency distributions of the final sample, n = 36
Frequency and percentage distributions of age groups
Age groups (years)
Number of times recorded (subjects)
% calculated on n = 36
Frequency and percentage distributions of classes of pre-test obesity
Classes of initial obesity (BMI, kg/m2)
Number of times recorded (subjects)
% calculated on n = 36
Obese class I (30.00–34.99)
Obese class II (35.00–39.99)
Obese class III (≥40.00)
Results for the obesity categories showed that overweight and obese class I were both the most frequented brackets with 12 subjects each (33.33 %), whereas only two subjects (5.56 %) were classified as obese class III.
The 36 participants had less weight after completing the programme; 83.85 ± 16.21 kg, as compared with their initial weight, 85.98 ± 16.28 kg. Further analyses showed that there was a statistically significant decrease of 2.13 [95 % confidence interval (CI) 1.82–2.45] kg, t(35) = 13.77, P < 0.0005, and a large effect, d = 2.30. Consequently, the H0 was rejected in favour of the H1.
The subjects also had a lower BMI; 32.15 ± 5.24 kg/m2, as compared with their initial BMI, 32.98 ± 5.32 kg/m2. Further analyses showed that there was a significant decrease of 0.83 (95 % CI 0.70–0.96) kg/m2, t(35) = 13.02, P < 0.0005, and a large effect, d = 2.17. Consequently, the H0 was again rejected in favour of the H1.
Discussion and conclusion
This was the first study that explored the physiological effects of Zumba on the body composition of a group (n = 36) of young and middle-aged women who were clinically overweight and obese, and who were exercising in non-laboratory conditions.
An 8-week Zumba programme consisting of twice weekly hourly sessions resulted in significant reductions (P < 0.0005) in the subjects’ weights (2.13 kg) and BMIs (0.83 kg/m2). In both weight and BMI differences, large effects were detected (d = 2.30 and 2.17, respectively). There was also 95 % confidence that the true mean differences for weight and BMI lay within the CI ranges (1.82–2.45 kg, and 0.70–0.96 kg/m2, respectively).
The study had several strengths. To start with, chance findings were statistically very low and the subjects were acting as their own controls. The discussion follows by considering the other strengths in detail.
Right sample size and good programme adherence
In spite the dropout rate of 12.20 % (adherence 87.80 %), adherence to structured interventions was reported as ‘good’ when at least 80 % of the participants completed a programme . Seventy-eight percent of these participants attended all the 16 sessions. Moreover, when the initial group (n = 41) dropped to 36, it was still more than the n required to sufficiently show any BMI differences (see ‘a priori calculations for sample size’).
As the last subject to drop out was only after the sixth session, it was unlikely that they stopped attending because the programme was not meeting their expectations from as early as the first six sessions or less. Attrition bias can therefore be ruled out.
Unaffected by genetic differences
Genes have been shown to modulate the phenotypic expression of obesity . However, as genetic factors are non-modifiable, they posed no threat to the single-group design due to the same pre- and post-intervention gene pool.
Considerable sample heterogeneity
The non-random sampling that was employed could have given rise to selection bias. Kim, Nitsch, Wang, and Bakhai  explained that it could happen because uncontrolled trials were likely to lead to enthusiastic results in favour of the intervention.
Literature shows that weight loss could be negatively associated with subjects’ ages [26, 27], and positively associated with their initial BMIs [28, 29]. This could have led to over-represent the sample with mostly young and very obese subjects as they seemed to be mostly susceptible to weight loss.
However, as subjects were recruited on a voluntary first-come-first-served basis with as wide ranges as possible for age and BMI (Table 2), sample homogeneity was not an issue. As shown in Tables 3 and 4, there were variances in the frequency distributions of age and BMI brackets, with only 8.33 % in the lowest age group and 5.56 % in the highest BMI category.
Low chances of instrumentation threat and measurement errors
Measurement errors were unlikely to occur because with the aid of a sensitive digital scale, body weights were recorded quite accurately to 0.1 kg. Furthermore, the same weighing scale was used in all measurements. The instrument was also calibrated according to standard procedures.
With one stadiometer, the participants’ heights were measured at eye level to the nearest 0.1 cm. Another precaution involved taking duplicate height readings. Furthermore, weight and height measurements were always recorded by the same researcher.
Quasi-controlled diurnal changes in body weight
As weight measurements were taken before the first and after the last sessions, and all sessions were held at the same time, the possibility of diurnal changes caused by eating, drinking, fluid retention and toilet activities was minimal. The indoor cooling system meant that temperature and humidity were somewhat constant.
Standardization of the subjects’ monthly cycles was however impossible. Furthermore, during the last session, the participants (as always), drank plenty of fluids. Nevertheless, the subjects were covered in sweat and most of them emptied their bladders before having their final measurements taken.
Low chances of testing threat
When taking the baseline measurements it could have been possible that some participants became more aware of their excess weights so that when they started the programme they were prepared for it in a way that they would not without the pre-test, and subsequently effecting the post-test readings. However, as the pre-post measures were based on normally non-reactive and routinely applied approaches, and the interval between the measurements was relatively long, it was unlikely that there could have been a testing effect .
All measurements were objectively recorded by the researcher. Self-reported data generally underestimated the prevalence of obesity, especially among overweight women .
Unlikely for the BMI differences to be affected by muscle mass changes
A drawback with BMI is its inability to distinguish between muscle and fat , thus providing only a crude measure of body fatness. However, none of the participants had the physique of an athlete. Furthermore, the participants performed aerobic exercises, which are generally associated with weight reduction due to fat loss . Therefore, the BMI difference was likely to be more indicative of fat loss and the chances of any weight gain due to muscle hypertrophy were quite low.
No concern for regression threat
For a perfect correlation between pre-post measures, there would be no regression towards the mean . As the SPSS output correlation values for pre-post weight and BMI were 0.998 and 0.997, respectively, there was no concern for such regression.
Current results comparable with studies on aerobics
Although the changes were obtained through twice weekly sessions, they were still comparable, albeit at somewhat lower values, with two similar studies on step aerobics that were held three times weekly. Gezer and Çakmakçi  and Arslan  obtained the following differences for weights and BMIs: 2.55 kg, 0.99 kg/m2 and 2.66 kg, 1.06 kg/m2, respectively.
Limitations and suggestions
Certain limitations were unavoidable. There could have been historical events (history threats) that occurred between the baseline and follow-up measurements that would be alternative explanations for the observed mean differences. Dietary factors, for example, could have confounded the results because some participants may have changed their diets from high- to low-fat foods. Another possibility is that the structured programme may have motivated the subjects to become more active outside the programme . For example, they may have done more walking than they usually did before they enrolled for the study.
Apart from diet and PA, the control of obesity is multi-factorial . It was felt that if participants were told that besides keeping the same nutrition and PA routines they also had to maintain their sleeping patterns and smoking habits and keep complying with certain drug dosage regimens, with so much requirements demanded from them, they could become confused and prone to drop out.
A control group is considered to be effective in ruling out single-group threats, but history threats could still occur and the researcher could never know what the participants in the intervention and control groups did in their private lives. The two groups could, for example, react differently to a dietary television programme or there could even be compensatory rivalry as mentioned earlier.
Although an 8-week period is not considered to be long enough for one to age and change considerably, due acknowledgement should still be made to the fact that people change with time (maturation threat), and age-related weight gain was possible . However, all the subjects lost some weight, with the lowest weight loss being 0.70 kg.
Variation in participants’ skills was another issue. Some subjects had never previously practised Zumba. This resulted in time lost on learning the basic dance moves, which probably resulted in less weight loss. By the third session, the unfamiliarity with Zumba was resolved.
Finally, statistically significant results are not necessarily clinically significant; the participants’ final BMI (32.15 kg/m2) was still above the healthy upper level (24.99 kg/m2). Further studies are, therefore, required to establish the effectiveness of Zumba as an exercise modality for weight loss. It is also being suggested to link any weight loss resulting from these studies with other variables such as percentage body fat and waist-to-hip ratios.
The author thanks Mrs. June Sampson and Prof. Antony Stewart from Staffordshire University for their support. Further acknowledgements go to the Malta Sports Council (KMS) and the Ministry of Health for allowing the author sufficient time to do the necessary research and preparations for this study. The permission from the KMS and the University of Malta to use their hall for the Zumba sessions is also appreciated. Gratitude is extended to the Zumba instructress, Ms. Johanna Refalo, who was an asset for the success of the programme. Further gratitude is expressed to the technical assistance of Mr. William Galea, a KMS Executive Officer. This paper was not supported by any funding body.
Conflict of interest
There was no conflict of interest to declare.