Factors associated with self-assessment of body weight in women who work out at fitness centers Fatores associados à autoavaliação do peso corporal em mulheres praticantes de academia

This study analyzed factors associated with self-assessment of body weight (SABW) among women who engage in physical exercises at fitness centers. Data collection was conducted at the largest fitness centers in the city of Presidente Prudente, SP, Brazil, with a sample of 200 women with a mean age of 25.5±9.7 years. A questionnaire with responses on a Likert scale was used to conduct SABW. Independent variables analyzed were: consulting with a nutritionist, chronological age, nutritional status (by BMI), perceived quality of life and marital status. The chi-square test and binary logistic regression were used for analysis (p<5%). A high proportion of women self-assessed their body weight in categories other than “normal” (59% [95%CI: 52.2–65.8]), and women with excess weight were more likely to do so (3.70 [95%CI: 1.83-7.49]), as were those with worse perceived quality of life (p=0.001). The women were asked which parts their bodies they wished to change and the abdominal region was the only part that had an association with selfassessment of body weight. There was a high rate of women who self-assessed their body weight in categories other than the option “normal” and this outcome was associated with worse perceived quality of life and having excess weight. Additionally, the major focus of concern for these women was the abdominal region.


INTRODUCTION
We are currently witnessing exponential growth in obesity rates in the global population.In response to this many different strategies have been adopted to control body weight 1 , both with people who regularly engage in systematic physical exercise and with people who do not 2 .
On the other hand, women have historically been more influenced by esthetic issues than men [3][4][5] , probably because of sociocultural aspects.The three most important sources of sociocultural influence are the family, peers and communication media, whether individually or, with greater impact, in combination.These influences can cause individuals to internalize beliefs and social messages about the importance of being slim in order to conform to contemporary stereotypes of beauty 6 .
Among women, this incessant quest for a slim body can contribute to adoption of behaviors that are harmful to health, such as bulimia and anorexia 1 .Furthermore, people who are affected by eating disorders suffer significantly compromised quality of life [7][8] .In contrast, among men the predominant ideal image is of a larger and stronger body, which has led to indiscriminate use of ergogenic resources in attempts to maximize performance 2,9 .
In counterpoint, engagement in physical exercise has been widely employed as a non-pharmacological tool for reducing the incidence of coronary disease, strokes, arterial hypertension and noninsulin-dependent mellitus 10 .In parallel, it can be observed that physically active people exhibit improvements in the various different components of physical fitness, which, in turn, confers countless health benefits, primarily when muscle mass is increased and body fat is reduced 10 .As a result, the long term effects of exercise on body weight appear to be more effective than merely adopting dietary restrictions 11 , particularly since adherence to such diets is very often motivated by consumption of non-scientific literature 12 .
Many unhealthy attitudes are the result of dissatisfaction with self image, predominantly dissatisfaction with aspects related to body weight, and this phenomenon is predominantly observed among women 13 .
Women tend to attempt to modify their bodies in such a way as to conform to specific standards, which they set for themselves as objectives.When these targets are not achieved, the result is even greater rejection of their own body image.
Along the same lines, it is notable that despite all of the metabolic, physiological, muscular and psychological benefits that result from the systematic practice of physical exercise, it is still common to read reports of people who are dissatisfied with their own appearance.It therefore appears undeniable that one of their objectives people who engage in physical activity wish to achieve is improvement of their esthetic appearance.
Although there is a vast body of published literature on the acute and chronic effects of physical training 10 , little is known about women's perceptions of their own body weight, and this is particularly true with reference to women who regularly work out at fitness centers.Information on their perceptions could be used to identify possible factors and/or behaviors which could help to improve their health and quality of life, when combined with regular physical exercise.
Therefore, the objective of the present study was to analyze factors associated with self-assessment of body weight (SABW) among women who engage in physical exercises at the largest fitness centers in city of Presidente Prudente (SP).

Sample
This was a descriptive, analytical, cross-sectional study conducted in 2011 in the city of Presidente Prudente, which is in the west of the state of São Paulo.The city center was excluded because there are no fitness centers there.The remainder of the city's Metropolitan district was divided into four geographic areas (North, South, East and West).In each of these four regions the number of customers registered at each fitness center was recorded and then, on an arbitrary basis, the largest fitness center in each of the four regions was chosen for the study, since all of them exhibited very similar demographic and socioeconomic characteristics.Therefore, data collection was conducted at four fitness centers in Presidente Prudente.
The first step was to make contact with the owners of each of the four chosen fitness centers and, once they had given approval, the researchers approached their female customers.Each fitness center provided a list containing the names of all of their female customers and all of the women who frequented these establishments were informed that the study would be conducted.
Questionnaires were then distributed to customers who had shown interest in taking part and who also met the following inclusion criteria: [i] females, [ii] who had not enrolled at the fitness center the same day, [iii] did not frequent any of the other three fitness centers under investigation, [iv] were over the age of 18 years, [v] and signed a free and informed consent form.Each participant completed her questionnaire on her own.Methodology described by Thomas, Nelson and Silverman 14 , was used to estimate a minimum sample size of 190 women for an expected prevalence of dissatisfaction with body weight of 55.9% 15 , a 7% sampling error and z=1.96.The resulting minimum number of women was then increased by a further 10% to cover expected future losses identified when inputting data, such as, for example: failure to respond to one of the items or failure to attend the anthropometric session for measurement of body weight (conducted using a Plena brand digital balance with a maximum capacity of 150 kg) and height (with a wooden stadiometer attached to the wall).After all necessary exclusions, the total number of women was n=200.
Each participant was given a letter explaining the study and containing a free and informed consent form.The study was approved by the Research Ethics Committee at the Universidade Estadual Paulista (UNESP) Faculty of Science and Technology, under protocol number 26/2009.

Dependent variable: self-assessment of body weight
Self-assessment of body weight (SABW) was conducted using the following question, "How would you rate your body weight?", which had the following possible responses (on a Likert scale): [i] very far below normal weight, [ii] a little below normal weight, [iii] normal, [iv] a little above normal weight and [v] very far above normal weight.For the purposes of statistical analysis, the outcome "SABW" was defined as all responses other than the option "normal".The women completed their questionnaires on their own, but there were two examiners who had been trained in advance on hand to clear up any doubts if requested.These measures were adopted to improve the quality of the data collected.
It should be noted that both the dependent variable and the independent variables were assessed using the same instrument.

Independent variables
The variables analyzed in this study are described in Box 1 below:

Statistical analysis
The chi-square test was used to test for associations between the dependent variable and the independent variables (Yates' correction was used for 2x2 contingency tables).Only independent variables that exhibited significant results according to the chi-square test (p<0.05)were added to the regression model.Binary logistic regression (with results given as odds ratios [OR] and their respective 95% confidence intervals [OR 95%CI ]) was used to analyze the association between the dependent variable and all independent variables, which were added to the model simultaneously.Variables that had been significant in the unadjusted model were then included in an adjusted model and adjusted OR values were calculated.The software employed for analyses was BioEstat, version 5.0 (Mamirauá, AM, Brazil).

RESULTS
The ages of the 200 women analyzed varied from 18 to 77, with mean age of 25.5±9.7 years, and they had from zero to four children.All of the women were participating in at least one type of physical activity available at the fitness centers (varying from 1 to 3 activities) and the median time since they had started attending these activities was 240 days (95%CI: 47.6-741).
Table 1 lists the variables associated with SABW.When compared to women with normal weight, overweight women had an approximately four times greater probability of stating they were "a little above normal weight" OR=3.70 (95%CI: 1.83-7.49).Additionally, women whose perceived quality of life was "regular" were more likely to have body dissatisfaction (OR=7.1495%CI: 2.36-21.6)than women with "excellent" perceived quality of life.
Table 2 lists associations between SABW and the parts of their bodies that the women stated they would like to change.OR= odds ratio; 95%CI= 95% confidence interval.
Women who self-assessed their weight in the categories "a little above normal weight" and "very far above normal weight" were most likely to want to change the appearance of their abdominal region (OR=3.76[95%CI: 2.06-6.86]).In counterpoint, those who reported no wish to change any part of their bodies exhibited an 82% lower probability of self-assessing their weight in categories other than "normal" (OR= 0.18 [95%CI: 0.06-0.52]).
When the variables that were significantly associated with SABW were used to construct a multivariate model, it was found that women who had manifested a desire to modify their abdominal region, who exhibited overweight, and who reported a regular and/or good perceived quality still had the highest probabilities of having SABW in categories other than "normal".Data on these associations are shown in Table 3.

DISCUSSION
The most important contributions made by the study are related to the description of self-assessment of body weight by women who practice physical exercise at the largest fitness centers in the city of Presidente Prudente, SP, Brazil.Analysis of the factors related to their physical condition revealed that more than half of the women in the sample self-assessed their body weight in categories other than the option "normal", that 52.5% self-assessed as overweight and just 6.5% assessed their own weight as below normal, and that 71.3% of these women were unsatisfied with their abdominal region.In this sample, 59% of the women investigated reported that their body weight was not within normal limits, which is a similar percentage to the 55.9% observed among adult women in Rio de Janeiro 15 , but a lower proportion than the 67.8% reported for 573 female students aged 8 to 10 years from Rio Grande do Sul 16 , which suggests that body dissatisfaction has onset at younger ages.There is evidence in the literature to show that the occurrence of dissatisfaction with body weight is more prevalent among women than among men 15 .One possible explanation for this high rate among women is the fact that they are constantly being urged by society and by the communication media to have slim bodies 17 .
On the other hand, recent national data on Brazil have revealed that more than half of the adult population is overweight 18 , and being overweight was also one of the variables associated with weight perception in the sample investigated here, although some studies suggest that this interaction occurs from adolescence onwards 16,19 .In the present study, overweight women exhibited an almost 4 times greater probability of reporting dissatisfaction in self-assessment of body weight than women with normal BMI, but these results are not unanimous.
According to the literature, body image is composed of two components: body esteem and body dissatisfaction.The first refers to the extent to which we like our own bodies in general, which can include aspects other than the weight and shape of the body, such as, for example, face, eyes, nose, mouth, neck, trunk etc.In contrast, body dissatisfaction is specifically focused on concerns about body weight, body shape and body fat 20 .Therefore, nutritional status appears to be associated with dissatisfaction with body image.
A study conducted in the state of Rio de Janeiro with 844 adults, 489 of whom were women, found that both men and women wished to weigh significantly less, with mean desired weight loss figures calculated by subtracting reported weight from desired weight of -1.85 and-3.30kgrespectively.In that study there was a significant difference between the two sexes among people from whom data was collected with relation to their perceptions of their weight to height ratio, with women classifying themselves into excess weight categories more frequently than men (43% versus 25%) 15 .
These findings appear to partially confirm the results observed in a study of 60 females living in the state of São Paulo, that used drawings of the human figure to conduct individual assessments during interviews, finding that obese women (n=30) produced more disproportionate drawings than women who were not obese.This could be associated with an inability to perceive their bodies as they really are, which in turn can be considered an indicator suggestive of distorted body image.Additionally, the same authors observed greater feelings of inferiority and dissatisfaction among these women 21 .
A study that analyzed dissatisfaction with body image stratified by sex, in a sample of 865 university students at a public institution in Florianópolis, SC, Brazil, found that the men were more likely to be dissatisfied with their bodies because they believed they were too thin (43.8%) than because of excess weight (34.1%), whereas the opposite was true of women, with a greater prevalence of dissatisfaction because of excess weight (62.4%) than because of excessive thinness (15.5%) 13 .
One possible explanation for the greater probability for women with excess weight to be dissatisfied than men appears to lie in the influence that the media and cultural aspects have over this population in today's society 22 .
Although certain very convincing results have been published in favor of the association between satisfaction or dissatisfaction with body image and aspects related to weight, a consensus has not yet been reached on this data because it is common for people to self-report that they feel fat even among samples with BMIs classified within normal limits 21,23 .These findings suggest that the subjective perception that people have about their bodies may, to them, be more important than their anthropometric profiles.
Excess weight can also be linked to psychological disorders and these can themselves influence people's self-assessment of their own bodies, caus-ing more intense states of dissatisfaction [24][25] .There are reports that problems that affect women with excess body weight and dissatisfaction with their own bodies may be related to psychological diseases such as depression [26][27][28] .
Dissatisfaction with body image can lead people to adopt strategies that are harmful to their bodies in attempts to achieve their desired weight.Such strategies include taking diuretics and laxatives, self-induced vomiting and extreme physical activity, among others 29 .
A study of 1,148 girls aged 10-19 years from the city of Florianópolis, SC, Brazil, that was conducted with the objective of identifying prevalence rates of the symptoms of anorexia nervosa and dissatisfaction with body image reported prevalence rates of 15.6% and 18.8% respectively, and demonstrated that dissatisfaction with body image was the greatest risk factor for manifestation of the symptoms of anorexia nervosa 29 .
In the present study, dissatisfaction with self-assessment of body weight was associated with worse perceived quality of life.This result has also been observed before, in young people from the state of Paraná 5 , among whom those with excess weight exhibited almost double the probability of reporting worse quality of life (OR= 1.78 [1.06-3.04]).One explanation for this finding may lie in the limitations that excess weight places on all of the body's organic structures, in addition to sociocultural and emotional issues that are also strongly associated with satisfaction with body weight 4 .
In our study, desire to change the abdominal region had a greater association with SABW and dissatisfaction than any other body part.However, no previous studies that have reported comparable results could be found.One study conducted with people who sought the services of a plastic surgery clinic in the city of São Paulo, SP, Brazil, found that the most often requested surgical procedure was liposuction (14% of cases) and that the greater proportion of the sample were women 30 .
The most important limitation to the present study lies in its crosssectional design which does not permit the establishment of relationships of causality between the variables.It therefore appears appropriate to suggest that future studies to analyze these associations be conducted with prospective designs and among younger populations.
The 7% sampling error that was allowed for in this study has an impact on its precision and so one should be wary of extrapolating the results to populations with different characteristics.
Another issue is the failure to measure reproducibility of data.The reason for this is that none of the participating fitness centers allowed the researchers to meet any of the women more than once (to measure reproducibility), because the people responsible for running the establishments believed that to do so could inconvenience their customers since all of questionnaires were completed at the fitness centers.
Finally, the lack of data on those women who preferred not to take part in the study or on women enrolled at other fitness centers should be taken into account because they could have had demographic, cultural and economic characteristics distinct from those who did participate in the study.

Box 1 .
Independent study variables

Table 1 .
Factors associated with Self-assessment of Body Weight (SABW) in women attending the largest fitness centers in the city of Presidente Prudente, SP, Brazil (n= 200).

Table 2 .
Parts of the body associated with Self-assessment of Body Weight (SABW) among women attending the largest fitness centers in the city of Presidente Prudente, SP, Brazil (n= 200).

Table 3 .
Multivariate model for associations between Self-assessment of Body Weight (SABW) and related factors in women who attend the largest fitness centers in the city of Presidente Prudente, SP, Brazil (n= 200).
* When the proportion is 100%, it is impossible to calculate odds ratios; OR= odds ratio; 95%CI= 95% confidence interval.