Introduction

Body image and related issues have been considered a Western phenomenon, but in recent years, these issues have become an evident health and social problem in Eastern societies [1]. Body concern increases in adolescence and can significantly influence self-esteem [2]. Body image and body satisfaction are influenced by many factors, including pressure from relatives, friends and media as well as self-esteem. Thompson et al. have developed the “Tripartite Influence Model” to describe the effect of these variables on body image [3], in which the ideal body promoted by the society and the media is adopted as a goal. For women, this ideal body is slim. Despite the influence of internalizing this ideal on body comparison, Thompson et al. argue that social comparison could in turn affect internalization [3]. Based on this model, appearance comparison and internalization of the thin ideal as mediators could lead to compensatory behaviors aimed at weight reduction [4].

This model has been used for the assessment of adolescent body image issues [5, 6]. Body-related concerns and behaviors vary with gender, age, and socio-cultural pressures. Thompson et al. introduced covariance structure modeling (CSM) that emphasizes mediator the comparison of some of the variables known to affect body image, such as self-esteem [3].

Teens wish to be attractive and to have an ideal body, a concept that is typically introduced by the media and is often difficult to achieve. Failure to achieve this ideal body can lead to impaired self-esteem, depression, isolation, suicidal thoughts, and compensatory behaviors such as dieting, inappropriate exercise, use of drugs, and eating disorders [7]. Women desire to be slim because it is viewed as a symbol of attractiveness, intelligence, success, and opportunity [8].

Attempts to attain this body ideal can lead adolescents to behave in dangerous ways. One population-based survey of adolescents showed that approximately 50 % of teen girls and 38 % of boys used unhealthy weight reduction methods. Dieting was the most frequently used method by 45–66 % of teen girls [9, 10]. Dieting can begin before adolescence; some studies have reported that approximately 40 % of preadolescent children have used dieting as a weight reduction method [11]. The incidence of dieting has been reported to increase to over 60 % during adolescence [10]. Unhealthy dieting can result in nutritional deficiency, impaired eating behaviors and even eating disorders, particularly in adolescence. Beginning to diet in adolescence is a contributing factor in the continuation or intensification of dieting and eating disorders in adulthood [9].

Although exercise is considered a healthy behavior, it can potentially be harmful when it is used as a way to lose weight. One form of harmful exercise is the so-called “compensatory exercise” used for weight reduction and the regulation of body shape [12].These behaviors are more frequent in females; one study reported that approximately 18 % of female college students had undertaken excessive exercise at least twice per week [13]. Women with a high level of concern regarding their body and attractiveness may try to achieve the portrayed ideal body through intense exercise, which may lead to lower body image satisfaction in addition to negatively impacting health [8]. Some studies have described higher body dissatisfaction in severe exercisers compared to those who exercise moderately or not at all [12]. In addition, females with greater body dissatisfaction experience higher negative consequences of exercise [12]. Research has shown that dieting, disordered eating, and other compensatory weight-reducing behaviors during adolescence can result in the maintenance or worsening of these habits in adulthood [14].

Previous studies have shown that body dissatisfaction and related issues are increasing in Iran [15]. Several studies have described the prevalence of body image issues and eating disorders in Iran. Nobakhat reported that weight concerns and weight management behaviors were frequent among adolescents in Tehran. She showed that approximately 48 % of teens exhibited behaviors aimed at weight reduction, and 17 % reported dieting [16]. In another study of college students in Iran, approximately 51 % of individuals reported some degree of body dissatisfaction. In this study, subjects with a higher degree of body dissatisfaction reported exercising more [17]; however, in this study, exercise was considered a lifestyle method and not a compensatory behavior; therefore, it is not surprising that these findings differ from our results. Hatami et al. showed approximately 75 % of female adolescents in Tehran exhibited some degree of body dissatisfaction [18], and approximately 56 % of adolescents used dieting as a weight reduction method [19]. In addition, 40 % exercised to be thinner [19].

Given the increase in body dissatisfaction and its effects, including eating disorders, in Eastern societies, the identification of factors during adolescence that are predictive of serious problems is important. Culture plays an important role in body dissatisfaction, and ideals of beauty and attractiveness differ among various cultures [1]. However, in recent years, body dissatisfaction has increased in Asian cultures [1, 15], and there are multiple differences between Asian cultures that affect an individual’s perceptions, attitudes and behaviors. Akiba argued that a lack of “body conscious information” such as Western media in Iran could result in higher body satisfaction among Iranian people [20]. Although there are no official statistics regarding the frequency of behaviors aimed at changing body shape, this study focuses on establishing the frequency of dieting and exercise as weight reduction behaviors in Iranian adolescent girls and the predictive factors for these behaviors.

Methods

This study was a part of large survey conducted in Kerman at the center of the largest province in Iran. The survey’s questionnaire was completed by 350 adolescent girls between 13 and 19 years old [mean (SD) age: 16.21(1.05)] in Kerman’s high schools. These girls were selected by quota sampling from both public and private high schools of different socioeconomic status. Informed consent was obtained from all individual participants included in the study.

We first applied logistic regression modeling. A series of multifactorial logistic regression models were applied to identify the factors influencing each of the outcomes or body management methods (i.e., diet and exercise). The results are presented in terms of the odds ratio (OR), associated confidence intervals (CI), and P value.

Classification and Regression Trees (CART) divide the subjects into nodes, and indicate the maximum homogeneity within nodes and maximum heterogeneity between nodes. Tree models provide simple rules that guide decision making. Because our outcome was binary, we constructed a classification tree to identify which girls were more or less likely to change their body shape. Tree-based models explore data to select the best variable with the clearest cutoff to create two groups with maximum homogeneity within each group and maximum heterogeneity between two groups. To divide the subjects into two groups, all independent variables were dichotomized at every possible cut off. Then, a measure of homogeneity was computed for all of them. The optimal variable and split was selected by comparing homogeneity indices.

In both groups, the same process was applied to create a tree structure; each parent node was divided into 2 child nodes, leading to the formation of a large tree. The Gini index is the most widely used criterion for measuring non-homogeneity and was calculated for all variables and cutoffs to select the optimal split at each branch.

To avoid over-fitting the tree, rules such as a minimum number of parent and child nodes are required. In this study, the minimum number of observations (i.e., sample size) for the parent and child nodes in the tree model was 30 and 10, respectively. To select a tree with minimum complexity and acceptable prediction ability, the final tree was pruned. Pruning was initiated at terminal nodes, which were deleted when their elimination resulted in a misclassification cost that was significantly lower than the reduction in complexity. The complexity parameter of the new tree was then calculated. This process continued until the root node was reached. Finally, complexity parameters were plotted against tree size (i.e., the number of terminal nodes), and the optimal tree was selected. Group membership was defined for all subjects, and the accuracy of the model was evaluated using sensitivity and specificity.

Measures

Outcome measurement

We asked respondents whether they followed any body change regimen (i.e., exercise or diet) during the last 12 months. The survey questions were based a study by Neumark–Sztainer et al. that probed the use of diet and exercise for weight reduction or body change. The test–retest agreement was approximately 97 % [9].

Profile characteristics

This section included age, educational grade, weight, height, parents’ education (i.e., illiterate, elementary, high school, or university) and economic status (i.e., fair, medium, good, or excellent).

Body image concerns

Body image was assessed using a questionnaire regarding body concerns and satisfaction [8, 21]. These questions focused on the importance of and satisfaction with weight and appearance. In this questionnaire, four items were used to assess body concerns, including “How happy are you with your weight?” and “How important to you is your weight?” Items were rated on Likert scale from completely satisfied (5) to completely dissatisfied (1).

BMI

Body Mass Index (BMI) was calculated in kg/m2 and was assessed according to a BMI chart based on age, sex, and four categories: underweight (<5th percentile), normal weight (between the 5th and 85th percentile), overweight (85th to 95th percentile) and obese (>95th percentile) for girls [22]. These cutoffs are appropriate for Iranian adolescents [23].

Socio-cultural pressure

The socio-cultural influences on body image and body change Questionnaire was used in this study [24]. Perceived pressures from mothers, fathers, friends and the media for weight loss were assessed using this questionnaire. Acceptable reliability and validity in adolescents were reported for this group using this instrument. Respondents were asked to complete this questionnaire based on a six-point Likert scale that ranged from never (1) to always (6). The items were simple questions such as Does your father (mother, best friend or media) encourage you to lose weight?’’. The summation of all question scores was considered the total score. Higher scores were interpreted as higher perceived pressure. The correlation among all sources of pressure ranged between 0.33 and 0.57 for the girls [21].

Rosenberg self-esteem scale

We used the Rosenberg self-esteem scale (RSE), which includes 10 global statements and total scores between −10 and 10. Positive scores indicated higher self-esteem, while negative scores were correlated with lower self-esteem. The Persian version of the Rosenberg self-esteem scale (RSE) exhibited acceptable psychometric properties [25].

Body dissatisfaction

To assess body dissatisfaction, we used a figure rating scale with appropriate psychometric properties (Persian version; test–retest reliability α = 0.79 and internal consistency α = 0.75) [21].This scale included nine silhouettes (male and female) numbered from 1 (very thin) to 9 (severely obese). The subjects were asked to identify the image most similar to their own current size and shape. They were also asked which image they would most prefer to be (ideal body type). Body dissatisfaction was assessed by calculating the absolute difference between the current and the ideal size [21, 26].

Results

The mean BMI of the girls was 20.44(3.41) and ranged from 14 to 34.72. Approximately 12.6 % of the girls have been overweight or obese. Parents’ educational level was similar: nearly 50 % of parents had a high school degree, and over 25 % had a university education. These girls exhibited different economic situations: 5.7 % fair, 6.1 % excellent, 41.7 % medium, and 41.2 % good. Table 1 presents the demographic data of the participants.

Table 1 Descriptive statistics of respondent characteristics and socio-cultural variables
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Thirty-five percent of the girls exhibited body satisfaction, while the rest exhibited various degrees of body dissatisfaction. Approximately 39.7 % of adolescent girls have attempted dieting to lose weight. In addition, 37 % of the girls have exercised for weight loss. We calculated the correlation between independent variables (Table 2) and found that BMI was positively correlated with body dissatisfaction, body concern, and perceived pressure from the mother and father. Furthermore, a positive correlation between all sources of pressure was observed. High pressure from the father and from the mother were positively correlated.

Table 2 Correlation between diet attempts and other variables
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The logistic regression model revealed that pressure from the mother and the media, the father’s education level, and BMI are contributing factors in diet attempts in adolescent girls. Pressure from mothers increased the risk of dieting 1.2-fold (95 % CI 1.062, 1.37; P value <0.001), and pressure from the media was associated with a 1.14-fold increase in dieting (95 % CI 1.030, 1.275; P value <0.001). A one unit increase in BMI was associated with a 22 % increase in dieting in adolescent girls (95 % CI 1.12, 1.33; P value <0.001). In addition, the father’s educational level was linked to a 1.5-fold increase in dieting attempts in their daughters (95 %CI 1.09, 2.20; P value <0.001; Table 3.).

Table 3 The identification of factors that encourage girls to diet for body shape management
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Three variables contributed to the construction of the tree: BMI, perceived pressure from the mother, and perceived pressure from friends. In total, four terminal nodes were created. We observed that 85 % of girls with a BMI <20 and mother pressure <8.5 did not follow diet regimes. For those with a BMI >20, the dominant factors were pressure from friends and the mother. The majority of subjects forming this subgroup (i.e., those with BMI >20) with low friend pressure (<12.5) and low mother pressure (<5.5) did not follow diet regimes.

Interestingly, 70 % of those with a low BMI (<20) followed diets when the pressure from the mother was high (>8.5). The other group with a high likelihood of dieting consisted of subjects with a high BMI and high perceived pressure from the mother and from friends (Fig. 1).

Fig. 1
figure 1

A decision tree for the factors influencing dieting attempts

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The use of exercise as a method for weight loss represented another variable. More than one-third of adolescent girls used exercise for weight loss. Logistic regression demonstrated that BMI (95 % CI 1.133, 1.331; P value <0.001) and perceived pressure from the media (95 % CI 1.150, 1.404; P value <0.001) increased the risk of exercise use as a weight loss method by 1.2-fold.

Four variables contributed to the construction of the tree: BMI, perceived pressure from the mother, perceived pressure from friends, and body dissatisfaction. In total, four terminal nodes were created. We observed that approximately 25 % of girls with a BMI <19 and perceived pressure from the media >3.5 attempted to exercise as a weight reduction method. For those with a BMI >19, the dominant factors were perceived pressure from friends and body dissatisfaction. The majority of subjects in this subgroup (i.e., those with BMI >19) with perceived pressure from friends (<10.5) and body concern (<10.7) did not use exercise as a weight reduction method (Fig. 2).

Fig. 2
figure 2

Decision tree regarding the influencing factors on attempts to exercise

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Conclusions

Although body dissatisfaction is increasing for both genders during adolescence, female teens are more likely to experience dissatisfaction. Over one-third of adolescent girls attempted to lose weight by dieting and heavy exercise [27]. In the present study, approximately two-thirds of the girls had experienced various degrees of body dissatisfaction. Previous studies conducted in Tehran revealed a high prevalence of body dissatisfaction thought to be related to the Westernized culture of this city. In spite of the fact that Iran is a country with multiple subcultures and ethnic groups, the body dissatisfaction reported in different studies was consistently high [17, 26]. In one study, a comparison between body image among Iranian women living in Iran and those living in America revealed no differences between the groups. This study concluded that exposure to Western media and acculturation was not related to body concerns and eating disorder symptoms [28]. It therefore appears that there is a cross-cultural preoccupation with body image, with aspects of culture-bound severity.

We found that body mass index (BMI) is an important factor in the attempt to lose weight, which is consistent with previous studies [29]. In girls with a BMI lower than 20, perceived pressure from the mother was a significant predictive factor. Our findings demonstrated that 70 % of daughters who perceived high pressure from their mother attempted to diet irrespective of BMI. In addition, perceived pressure from the mother was found to be a contributing factor for intense exercise. Pressure from peers and the media were also important factors in the decision to lose weight. Based on our decision tree model, BMIs of 20 and 19 were taken as cut-off points for attempting to diet and for intense exercise, respectively. Although in some studies weight status was not a significant factor in adolescent dieting, in a study of body change behaviors in the general population, we found that BMI was an important predictive factor of attempts to diet [21]. Given that the prevalence of obesity in the Iranian population under 18 years of age (overweight: 5–13 %; obesity: 3–12 %) [30]. BMI is a serious potential predictor of unhealthy weight reduction management in adolescents.

Cultural values affect the perception of oneself and of others. Therefore, feedback regarding physical appearance can have a significant impact on body image [3]. One such form of feedback arises from close interpersonal relationships with peers, parents, and partners The family is the first institution to form individuals’ attitudes, values, and behaviors, and the parents’ influence may manifest in many ways, including dietary habits, attitudes regarding physical appearance and attractiveness, and encouragement for body change behaviors via positive or negative feedback about ideal appearance. In one study, between 61 and 63 % of teen daughters reported perceived pressure from their parents regarding eating and caloric restriction [31, 32].

Parental attitudes and the pressure to be thin increases the likelihood of body dissatisfaction and eating disorders. Parental comments regarding dieting sometimes begin in childhood and persist into late adolescence [33]. Although some studies have argued that there is no difference between maternal and paternal encouragement of a daughters’ dieting, the present study demonstrates that perceived pressure from the mother was a more important predictor of dieting in teen girls, a finding in agreement with other studies [31, 34, 35].

Some researchers have argued that pressure from mothers influences eating behaviors such as dietary restraint [21–37], while pressure from fathers has been associated with exercise behaviors [21]. In the present study, mothers had an effect on both dieting and intense exercise. This could be due to the close relationship between mothers and daughters in Asian cultures, whereas the relationship between fathers and daughters is slightly more formal. Understanding the nature of parent-adolescent relationships in Asian cultures may be effective in planning the prevention of unhealthy body change behaviors.

Peers play a similar role in teen body dissatisfaction. In addition, social support and the acceptance of peers are other important factors [36, 37]. One study showed that approximately 50 % of teen girls were influenced by their mothers, female friends, and sisters regarding weight loss [37]. Studies have suggested that body dissatisfaction and dieting using unhealthy weight reduction programs are influenced by the opinion of peer groups regarding the perfect weight and body [34]. One study reported that of teen girls with friends who dieted “very much,” approximately two-thirds attempted to diet themselves; this contrasted with about one-third of those whose friends did not diet [38]. Body comparison and modeling may be the cause of this phenomenon.

Unrealistic and idealized advertised images can play an important role in body dissatisfaction. Over the last decade, technology has resulted in the manipulation of these images to be more attractive than reality. Individuals, particularly teens, who feel pressured to achieve an idealized body are prone to dieting and intense exercise.

One important factor in body dissatisfaction and unhealthy weight reduction is the media. Hargreaves and Tiggemann reported that females who watched appearance-related commercials experienced greater body dissatisfaction [39]. One study reported that media pressure in forming a perception of the ideal body (thinness) may be the only significant factor influencing body dissatisfaction [40]. Media effects may be related to the amount of time spent watching idealized beauty advertisements and reading fashion magazines [39]. Researchers have argued that Western media influences on body image are derived from cultural context [41, 42]. Examples of these cultural factors can be seen in the differences in body dissatisfaction between Japanese and Taiwanese university students, who are exposed to similar Western impacts [43], or in Chinese adolescents [44]. However, it seems that other factors contribute to this effect. In Iran, the use of women in advertisements is forbidden, and male models are fully clothed. However, indirect media influences are present in the form of TV and cinema stars (albeit in full dress or a hijab) and in advertisements for various diets, thinness instruments and drugs, and cosmetic surgery.

In our study, as in previous studies, we found that similar risk factors affect body change behaviors, but that several predictive factors may have a cumulative effect on outcome [15, 31]. It is also possible that the lack of effect of some of possible factors (e.g., self-esteem) may result in stronger effects than other main factors.

The results of this study might aid in the prevention of the serious physical health and psychological side effects of body image dissatisfaction. Parents and institutions such as schools should be familiar with these issues. Parents must be aware that their comments and behaviors regarding the ideal body may have damaging effects on the body image of their children, with compensatory consequences. Studying the effects of fathers’ opinions on the behaviors of their children in Asian cultures would help the creation of better preventive and interventional programs.

In west Asian countries, religion (i.e., Islam) is considered a socio-cultural factor in body satisfaction. Religion can play a protective role against body dissatisfaction [45, 46], although Dunkel has suggested an increased risk of developing a negative body image in younger and older Muslim women [47]. In Iran, most people (more than 98 %) are Muslim, and although recent research has not focused on religious attitude, the role of Islam should be considered.

The current study has some limitations, such as a narrow range of participant age and a cross-sectional design. Future studies with a wider range of participants and a longitudinal design could help to gain a better understanding of the factors contributing to body change behaviors in Asian adolescents. In addition, our sample size was not high enough to produce robust results. Although we tried to reduce over-fitting by pruning the final tree, independent data sets are required to assess the generalization of our results.