Body Satisfaction Running head: BODY SATISFACTION Temporal Trends in Body Satisfaction and Weight Controlling Behaviors Among US High School Students 1999-2007 Andrea E. Kirby Vanderbilt University 1 Body Satisfaction 2 Table of Contents Table of Contents ............................................................................................................................ 2 Abstract ........................................................................................................................................... 4 Temporal Trends in Body Dissatisfaction and Weight Controlling Behaviors .............................. 5 Spread and Internalization of the “Thin Ideal” ........................................................................... 5 Harm of Body Dissatisfaction ..................................................................................................... 5 Poor Nutrition ......................................................................................................................... 5 Unnecessary Restriction.......................................................................................................... 6 Eating Disorders...................................................................................................................... 6 Depression............................................................................................................................... 7 Economic Costs ...................................................................................................................... 7 Background ................................................................................................................................. 8 Prevalence ............................................................................................................................... 8 Women at Risk........................................................................................................................ 9 Body Distortion as a Measure of Body Dissatisfaction ........................................................ 10 Limitations of Current Literature .......................................................................................... 10 Rationale for Approach ............................................................................................................. 11 Questionnaire ........................................................................................................................ 11 Large, Representative Sample of Adolescents ...................................................................... 11 Long Time Span to Analyze Change Over Time.................................................................. 12 Specific Aims ............................................................................................................................ 12 Method .......................................................................................................................................... 14 Overview ................................................................................................................................... 14 Participants ............................................................................................................................ 14 YRBSS Data Sets .................................................................................................................. 14 YRBSS Sampling Methods....................................................................................................... 15 Sampling ............................................................................................................................... 15 Weighting .............................................................................................................................. 16 Response Rates ..................................................................................................................... 16 Data Collection ..................................................................................................................... 17 Data Processing ..................................................................................................................... 17 Study Variables ......................................................................................................................... 17 Demographic Variables ........................................................................................................ 17 Key Variables........................................................................................................................ 18 Derived Variables ................................................................................................................. 19 Weight control factors....................................................................................................... 19 Weight satisfaction............................................................................................................ 20 Design ....................................................................................................................................... 21 Data Preparation.................................................................................................................... 21 Data Analysis ........................................................................................................................ 21 Results ........................................................................................................................................... 23 Sample Description ................................................................................................................... 23 Models................................................................................................................................... 26 Change Over Time ................................................................................................................ 27 Hypothesis one: increase in body dissatisfaction over time. ............................................ 27 Body Satisfaction 3 Hypothesis two: decrease in healthy behaviors & increase in extreme behaviors over time. .................................................................................................................................. 28 Gender and Ethnicity Differences ......................................................................................... 30 Hypothesis three: greater body dissatisfaction and weight control behaviors among females. ............................................................................................................................. 30 Hypothesis four: greater body dissatisfaction and weight control behaviors among Caucasians......................................................................................................................... 34 Relationship between Body Dissatisfaction and Weight Control Behavior ......................... 38 Hypothesis five: positive association between body dissatisfaction and weight control behaviors. .......................................................................................................................... 38 Hypothesis six: greater prevalence of body dissatisfaction and weight control behaviors among older adolescents. .................................................................................................. 39 Discussion ..................................................................................................................................... 44 Major Findings .......................................................................................................................... 44 Limitations ................................................................................................................................ 46 Implications............................................................................................................................... 47 Future Research ........................................................................................................................ 48 References ..................................................................................................................................... 50 Body Satisfaction 4 Abstract Background: Dissatisfaction with the size, weight, and shape of one’s body contributes to the risk of developing an eating disorder. Body dissatisfaction appears common among adolescents, but there is little information available on changes in prevalence over time. Purpose: We aim to study temporal changes in body dissatisfaction and eating disordered behavior between 1999 and 2007 and their relationship in high school aged youth. Methods: The National Youth Risk Behavior Survey (YRBS) data sets were downloaded from the Centers for Disease Control and Prevention (CDC) for the years 1999, 2001, 2003, 2005, and 2007. A pooled data set of variables common across the years was created (n= 64,270). Hypothesis: We hypothesize that the prevalence of body dissatisfaction and weight control behaviors will increase over time. We predict prevalence differences based on gender, ethnicity, and age. We also predict a correlation between body dissatisfaction and weight control behaviors. Data Analysis: The YRBS uses a multistage probability sampling design. We conducted univariate descriptive analysis with SPSS using case weights and multivariate hierarchical hypothesis testing with AM Statistical Software, which takes into account correlated errors within sampling units and utilizes design weights. Results: Consistency of body satisfaction and weight control behaviors was found over time. White adolescents and females seem at high risk of body dissatisfaction and eating disorder behavior. Body dissatisfaction and extreme weight control behaviors were positively related and fairly stable across age. Implications: Future research should study younger populations to improve understanding of etiology and effectiveness of body dissatisfaction and eating pathology preventions. Body Satisfaction 5 Temporal Trends in Body Dissatisfaction and Weight Controlling Behaviors Spread and Internalization of the “Thin Ideal” Body dissatisfaction—unhappiness with one’s size, shape, or weight—pervades Western culture and appears to be spreading. Alongside the spread of body dissatisfaction, the “thin ideal” of women has also developed. Internalization of the “thin ideal” occurs when an individual adopts a cultural ideal of thinness and accepts it as his/her personal standard. Because culture has such a great influence on body image (Dolan, Birtchnell, & Lacey, 1987), the cultural spread of the “thin ideal” and its internalization present a threat to well-being (Austin & Smith, 2008). The problem of body dissatisfaction is associated in the development of eating disorders (Stice & Shaw, 2002), leading to death and economic burdens. Furthermore, “given the recent widespread dissemination of this message in the media, it is unclear what the cumulative effect of this message may be on psychological functioning and weight control practices” (Roehrig, Thompson, & Cafri, 2008). Therefore, additional research is needed to grasp the scope of the spread of the “thin ideal” and its impact on weight controlling behaviors. Harm of Body Dissatisfaction Poor Nutrition One of the implications of the spread of the “thin ideal” may be body dissatisfaction, which correlates with poor quality of food intake. Specifically among adolescents, an age group that tends to lack appropriate knowledge of nutritional needs (Nelson, Lytle, & Pasch, 2009), poor body image plays a strong role in poor nutrition. Among children dissatisfied with their bodies, boys tended to cut out desserts, girls tended to eat less meats and carbohydrates (such as French fries and potato chips), and neither ate more fruits and vegetables (Middleman, Vazquez, Body Satisfaction 6 & Durant, 1998). In Middleman, Vazquez, and Durant’s study, “feeling too fat,” the main reason cited for weight-loss attempts, tended to result in a restrictive eating style. Predominately seen in females, this severely restrictive eating style fails to supply the nutrients, vitamins, and energy necessary for optimal growth and development in adolescence (Wahl, 1999). Unnecessary Restriction Another unhealthy behavior associated with body dissatisfaction is unnecessary food restriction. Female dieters are more likely to inaccurately estimate their weight, weigh more, and perceive themselves as heavier than non-dieters, thereby contributing to more dieting (MossavarRahmani, Pelto, Ferris, & Allen, 1996). Furthermore, increased dieting behavior predicts the development of both sub-threshold eating disorders and eating disorders. This finding led Stice and Shaw to conclude that body dissatisfaction can lead to dieting, which can lead to eating disorders (2002). For example, restrictive eating in which hunger cues are denied and meals are skipped may lead to overeating, binge eating, and/or weight gain (Spear, 2006). Thus, body dissatisfaction that results in restrictive eating has many potentially harmful effects. Eating Disorders The most severe complication of body dissatisfaction is arguably the development of eating disorders, which can be fatal (Howlett, McClelland, & Crisp, 1995). Body dissatisfaction was the greatest single predictor within the eating disorder inventory for the development of partial syndrome eating disorder within a 4-year period among the high school females that Stanford University of Medicine followed (Killen et al., 1996). This supports a link between body dissatisfaction (and weight concerns in general) and later development of partial syndrome eating disorder (a particularly strong link given that this study was prospective and done over 4 Body Satisfaction 7 years). Accordingly, body dissatisfaction, which is a precursor and risk factor for the development of eating disorders, can lead to the severe health complications that are seen in eating disorders. These include a range of health problems, such as osteopenia, osteoporosis, impaired pregnancy and child rearing ability among women (Treasure & Szmukler, 1995), dental deterioration, gastric or esophageal rupture (Rome & Ammerman, 2003), and even premature death (Sullivan, 1995). Depression Depression, both clinical and sub-clinical, is another potential consequence of eating disorders. The presence of eating disorder during adolescence predicts an increased risk for later development of depression, but depression does not significantly predict later development of eating disorders (Marmorstein, von Ranson, Iacono, & Malone, 2008). Unfortunately, Marmorstein, von Ranson, Iacono, and Malone did not directly test the causal relationship between eating disorder and development of depression. Also, a predominately Caucasian sample may threaten the external validity of their study. However, the study’s epidemiological nature and longitudinal data strengthen its conclusions, which converge with other research. For example, Stice and Bearman also found that body dissatisfaction and eating disorders predict later development of depressive symptoms, particularly in adolescent females (2001). Economic Costs Body dissatisfaction also places a substantial economic burden on those directly and indirectly affected by it. In Germany in 1995, the economic cost of anorexia nervosa alone was estimated to be 65,000,000 euros, and 10,000,000 euros for bulimia nervosa (Simon, Schmidt, & Pilling, 2005). These estimates include health costs, such as inpatient treatment, clinical therapy, Body Satisfaction 8 and doctor appointments. Insurance companies and welfare programs often contribute to the costs associated with these disorders, affecting society at large. Most figures underestimate the costs of body dissatisfaction that sometimes develops into disordered eating, thus the true cost of body dissatisfaction to society is likely larger than most realize. Between poor nutrition, unnecessary dietary restriction, and the development of mental disorders, the consequences of body dissatisfaction can be severe on individuals that it directly affects, as well as a society that carries the economic burden of associated disorders. Background Body dissatisfaction, the negative subjective evaluation of one’s body, is a substantial health concern that faces the world today. While the spread and potential harm of body dissatisfaction is well documented in the literature (Grogan, 1999), the onset and temporal trends of body dissatisfaction are comparatively understudied. Accompanying the growth of body dissatisfaction is the growth of obesity (Anderson, Eyler, Galuska, Brown, & Brownson, 2002) (Flegal, Carroll, Kuczmarski, & Johnson, 1998), eating disorders (Keski-Rahkonen et al., 2007), and related premature death due to chronic illness among the adult population (Agras, 2001). Research into body dissatisfaction and its consequences among adolescents indicates that body dissatisfaction is prevalent and problematic. However, more research among adolescent populations is necessary to understand the onset, temporal trends, and strategies for the prevention of body dissatisfaction. Prevalence The rising rates of eating disorders, of which body dissatisfaction is a precursor, among adults further emphasizes the need for additional research in the area. In the United Kingdom the Body Satisfaction 9 incidence rate of anorexia nervosa rose from 4.2 per 100,000 people in 1993 to 4.7 per 100,000 people in 2000 (Hoek, 2006). This incidence rate provides more information on the growth of anorexia nervosa among the population than its prevalence rate and emphasizes the continued growth and spread of eating disorders. However, because anorexia nervosa is chronic and difficult to treat, incident rates may lead some to underestimate the prevalence of eating disorders. Although anorexia nervosa is more fatal than bulimia nervosa, bulimia nervosa is more prevalent. Estimates suggest that 13.5 per 100,000 adult females develop bulimia nervosa every year (Hoek, 2006). These rates are commonly accepted as underestimates of the actual prevalence of eating disorders, and therefore new research is necessary to gain a more accurate picture of the prevalence of eating disorders and its related precursors (such as body dissatisfaction). Furthermore, these estimations focus on adult populations and tend to overlook the development of eating disorders among adolescents. Women at Risk Literature also suggests that women are at greater risk for body dissatisfaction, which translates into increased risk for eating disorders (Fairburn & Harrison, 2003). Not only are women more likely to dislike a particular body part, but also they are more likely to overestimate perceived weight (an established predictor of anorexia nervosa) and be dissatisfied with their current weight (Dolan et al., 1987). The implication that women are at a greater risk for body dissatisfaction than their male counterparts is strong. Interestingly, Dolan et al. also attribute this trend, and the withdrawal of 6 women from the study upon learning that their weight would be measured, to society’s “thin ideal” of women (Dolan et al., 1987). Although the more in-depth assessments used in the study improve the quality of its measurements, it also harms the quality of the study. For instance, Dolan could only manage 100 participants in the study. Such a small Body Satisfaction 10 sample size hinders the internal validity of the study, and therefore creates a need for larger sample sizes that are more likely to accurately represent the population. Body Distortion as a Measure of Body Dissatisfaction While not perfect, body image “distortion” is a useful operational definition of body dissatisfaction for studies on a larger scale. Research indicates that body image distortion among people with eating disorders is not an issue of perceptual deficit, but likely a cognitive process (Cash & Deagle, 1997). Perhaps so-called body distortion is intentional, or at least has some utility for those who adopt it. (Overestimation of normal body weight may serve as a greater motivator to lose unwanted weight than an accurate estimation, whereas underestimation of overweight may reinforce a desire to avoid exertion often required to lose weight.) Although some ambiguity remains around body image distortion and its mechanism in poor body image, it can be a useful indicator of body dissatisfaction (Brug, Wammes, Kremers, Giskes, & Oenema, 2006). More research into the predictive validity of body image distortion for body dissatisfaction may prove its utility in prevention studies among typical populations. Limitations of Current Literature While literature has provided insightful indicators of risk factors for body dissatisfaction and eating disorders that can be aimed at prevention, current literature has failed to fully address the needs to study adolescent populations, use large sample sizes, and analyze trends over time. Research is heavily weighted on adult populations, rather than adolescent populations, in which eating disorders develop and onset at higher rates (Diagnostic and Statistical Manual of Mental Disorders, 2000). There is also a lack of recent research on large sample sizes, covering multiple ethnicities and regions within the United States. However, the most palpable gap in the literature Body Satisfaction 11 is a trend analysis of body dissatisfaction and related behaviors across multiple years. This study aims to fill in these gaps. Rationale for Approach Questionnaire This observational study utilized the questionnaire approach, because it provides insight into the emotions, attitudes, and beliefs of a participant that form his/her body image, as well as demographics associated with body dissatisfaction. A national survey of overweight and obese women concluded that body dissatisfaction predicts weight loss efforts better than actual body mass index (Anderson et al., 2002). Questionnaires, such as this one, allow for greater sampling sizes and may also generate more discussion and leads for areas of research, but lack causal conclusions. For instance, Anderson and colleagues were able to conclude that weight loss efforts and body dissatisfaction are correlated, but a directionality problem remains: which one promotes the development of the other? Despite a few drawbacks, the questionnaire approach is effective for investigating body satisfaction (which is largely an internal construct), obtaining large sample sizes to improve validity, and generating research leads. Large, Representative Sample of Adolescents The growing rates of body dissatisfaction, behaviors symptomatic of eating disorder, and—predictably—eating disorders among adolescents are alarming. For example, 57% of females and 31% of males in their senior year of high school reported eating disordered behavior (such as binge eating or unhealthy efforts to lose weight like taking diet pills, intentionally skipping meals, fasting, smoking cigarettes, and purging) in the 1998 Minnesota Student Survey (Croll, Neumark-Sztainer, Story, & Ireland, 2002). These high rates of behavior, which are Body Satisfaction 12 precursory to and evident of eating disorders among adolescents, suggest that body dissatisfaction does not suddenly spring up in adulthood, but rather develops earlier. Therefore, further research on the onset, trends, and causes of body dissatisfaction among young adolescents needs to be performed. A limitation of the Minnesota study is that the sample was limited to students in Minnesota. Thus, new research should use nationally representative samples in order to improve external validity and large sample sizes to improve internal validity. Long Time Span to Analyze Change Over Time The rise in eating disorder behavior among adolescents is dangerous, harmful, and requires society’s immediate attention (Forman-Hoffman, 2004). Forman-Hoffman commendably used the Youth Risk Behavior Survey from 1999 for her data, making her sample more representative of adolescents living in the United States and her conclusions more easy to generalize to the United States healthcare and education systems than Croll, Neumark-Sztainer, Story, and Ireland’s study (2002). However, the survey from 1999 now seems outdated. Thus a more recent survey would be more relevant and useful for assessing the current condition of body dissatisfaction and eating disorder behavior among adolescents. Additionally, analyzing several surveys over time would provide insight into any trends and patterns in body dissatisfaction and disordered eating, as well as minimize error due to extrapolation. Specific Aims This study aims to address how body dissatisfaction has changed in the past 10 years among high school students in the United States and examine corresponding trends in weight control efforts. Based on risk factors indicated in previous research, gender, ethnicity, and age, differences were analyzed, as well as the relationship between body dissatisfaction and eating Body Satisfaction 13 disorder behavior. Ultimately, this study tackles the theory that external situations influence internalized cognitions and attitudes (such as body dissatisfaction), which predict behavior (such as eating disorder behavior). Research hypotheses include: 1. Increased body dissatisfaction over time 2. Decrease in healthy behaviors (such as nutritional food intake and moderate exercise) and increase in extreme weight control behaviors over time 3. Greater body dissatisfaction and weight control behaviors among females 4. Greater body dissatisfaction and weight control behaviors among Caucasians 5. Positive association between body dissatisfaction and weight control behaviors 6. Greater prevalence of body dissatisfaction and weight control behaviors among older adolescents Body Satisfaction 14 Method Overview Participants The population of interest was all high school students in the United States. Participants, ranging from ages 12 to 18 and of various ethnicities, were randomly selected for sampling. YRBSS Data Sets This study used preexisting data from the national Youth Risk Behavior Surveillance System (YRBSS), which the Center for Disease Control and Prevention (CDC) developed to assess the occurrences of health risk behaviors among high school students on an ongoing basis. Data was collected from high school students across the United States based on student responses to a questionnaire. The 1999 YRBS was the result of an extensive update of previous versions of the YRBS in which 11 questions were deleted and 16 questions added (to ensure that behaviors most closely related to mortality risk, and for which effective interventions have been established, were included). Of particular importance to the study of body dissatisfaction were the additions of self-reported weight and height to the questionnaire in 1999. Thus, this study analyzed data from the 1999 YRBS to the most recent 2007 YRBS. The questionnaire was given to test sites in the form of a booklet, which computers scanned to determine student responses and ensure consistency. The national survey contained multiple-choice questions in 6 categories of health behavior with 5-8 additional questions pertaining to health (that do not fall into one of the 6 categories). An example question follows: Body Satisfaction 15 Which of the following are you trying to do about your weight? A. Lose weight B. Gain weight C. Stay the same weight D. I am not trying to do anything about my weight. Overall, the YRBSS has been found to be reliable. However, a version of the questionnaire from 1999 had ten questions with questionable test-retest reliability (Brener et al., 2002). Nevertheless, YRBS self-report responses, particularly among high school-age adolescents, are considered valid (Brener, Billy, & Grady, 2003). For example, after completing the YRBSS twice in two weeks, 2,965 students were weighed and measured to determine the validity of self-reported weight and height. Although the CDC study found that the self-reports were very reliable, it also found that students tended to underreport their weight by 3.5 pounds and over-report their height by 2.7 inches (Brener, McManus, A., Lowry, & Wechsler, 2003). While not perfect, it appears that the YRBSS is a fairly reliable and valid tool for measuring health risks and behaviors associated with body dissatisfaction and disorder eating. YRBSS Sampling Methods Sampling The YRBSS employed three-stage cluster sampling. First, sixteen strata were formed from the 50 states and the District of Colombia based on metropolitan statistical area and minority populations to ensure representative samples. Then the primary sampling units, which are about the size of a large county, were randomly selected from these strata. The second stage of sampling selected private and public schools of varying sizes. To ensure similar sample sizes, individual classrooms were selected for the third stage of sampling. Body Satisfaction 16 Weighting Individual cases were weighted based on sex, ethnicity, and grade to ensure that the sample was representative of students in 9th through 12th grade in the United States. For instance, because black and Hispanic students were over-sampled to ensure accurate assessment of a smaller subset of the population, weighting corrected for this over-sampling. This was done through an iterative process in which extreme sampling weights were trimmed, resulting in an overall sample that was representative of the population of high school students in the United States on the basis of sex, ethnicity, and grade (Potter, 1990). In addition to over-sampling, weighting also helped to correct for non-response. Response Rates The YRBSS sampled without replacement, which prevented non-measurable bias due to non-response from entering the sample. As can be seen in Table 1, student response rates were higher than school response rates over all five years studied. The mean school response rate was 78%, whereas the mean student response rate was 84%. Therefore, the mean overall response rate was 66%. Ultimately, non-response might have introduced some bias into the data. Table 1 Response Rates Year Response Rate School Student Overall 1999 77% 86% 66% 2001 75% 83% 63% 2003 81% 83% 67% 2005 78% 86% 67% 2007 81% 84% 68% Mean 78% 84% 66% Body Satisfaction 17 Data Collection Participant welfare and consistency were stressed throughout data collection. Parental permission for data collection was obtained for each participating student according to local guidelines. Therefore, according to local guidelines, permission from participants’ parents was established either actively (prior to participation) or passively (after participation). Students voluntarily participated in completing the survey during a class period. Using cover sheets for responses on answer sheets or standard booklets and sealing recorded responses after questionnaire completion ensured student privacy. To ensure consistency in the process of data collection, trained data collectors visited students’ schools to explain the study using a standardized script and distribute the questionnaires. Data Processing After data was collected, the ORC Macro (a research and information technology firm) and the CDC processed the data. ORC Macro scanned the raw data and then sent it to the CDC to be compiled it into one data set. The CDC used SAS and Visual Basic to run quality control on the data (looking for missing responses, logical inconsistency between responses, and responses that are out-of range). Questionnaires with less than twenty acceptable responses after logical editing were removed from the data set. The CDC then returned the cleaned data set to the ORC Macro for weighting. Study Variables Demographic Variables A list of each demographic variable and how they were operationalized follows. Body Satisfaction 18 BMI: Students were asked how tall they are and how much they weigh without their shoes on. From these responses, body mass index in kilograms per square meter (kg/M2) was calculated using SPSS. Age: Students were asked whether they were 12 or younger, 13, 14, 15, 16, 17, or 18 or older. Grade: Students were asked their current grade and provided the options: 9th, 10th, 11th, 12th, or other or ungraded. Gender: Students were asked to indicate whether they were male or female. Ethnicity: Students reported their ethnicity from these options: Indian/ Alaska Native, Asian, Black or African American, Hispanic, Latino, native Hawaiian or Pacific Islander, White, or Multiple- Hispanic, or Multiple-Non-Hispanic. Based on the distribution of the results, the data were condensed into 4 categories: non-Hispanic white, non-Hispanic black, Hispanic, and multiple or other. Key Variables Main study variables varied from the year of data collection to self-description of weight and weight control variables. A list of each key variable and how they were operationalized follow. Year: The year variable describes the year the data was collected for the national survey, which takes place every other year. Describe Weight: Students were asked how they describe their weight and given the options: very underweight, slightly underweight, about right, slightly overweight, or very overweight. Body Satisfaction 19 Exercise: Exercising to control weight is operationalized as a positive response to exercising within the past thirty days to lose or maintain current weight. Diet: A positive response to eating less food, lower calorie food, or food low in fat in the past thirty days in order to lose or maintain current weight was considered dieting. Fast: Fasting was operationalized as a positive response to not eating for 24 hours or longer within the past thirty days in order to lose or prevent gaining weight. Diet Pills: A positive response to taking diet pills, powders, or liquids without a doctor’s approval in order to lose weight or prevent weight gain within the past thirty days was categorized as taking diet pills. Purge: Purging was operationalized as a positive response to vomiting or taking laxatives to lose or maintain current weight within the past thirty days. Derived Variables Weight control factors. Due to the large amount of behavior variables, they were reduced to a smaller set of scores. A factor analysis of these variables was performed using principal components with varimax rotation. The result was three factors, which are presented in Table 2. Factor one represents healthy food intake consisting of fruit, potatoes, carrots, and other veggies. Factor two represents vomiting/ laxative use, diet pill use, and fasting and is named extreme weight control behaviors. Finally, the third factor, weight loss strategies, consisted of exercising and dieting to lose weight. Factor scores were computed for all cases on each of the three factors. These factor scores are uncorrelated and represent three independent dimensions of eating behavior. Body Satisfaction 20 Table 2 Eating Behavior Factor Scores Variable Other vegetables 4-6 times a week Carrots 4-6 times a week Fruits 4-6 times week Potatoes 4-6 times a week Vomit/laxative use for weight control Diet pills for weight control Fasting for weight control Exercise for weight control Diet for weight control Factors Healthy Extreme Weight Food Control Behaviors 0.686 -0.661 -0.638 -0.586 --0.759 -0.711 -0.681 ----- Weight Loss Strategies -------0.844 0.785 Weight satisfaction. A new variable, Weight Satisfaction Index (WSI), was used as an indication of body dissatisfaction. Before constructing the WSI value, the self-reported body mass index (kilograms/ meters squared) variable was standardized based on age and gender (ZBMI). WSI was constructed to represent the deviation of actual ZBMI from the average of one of five groups based on self-rating of weight. Thus, in order to obtain the WSI variable 0.32 was added to the ZBMI of people who rated themselves as very underweight and 0.49 was added to the ZBMI of people who rated themselves as slightly underweight. People who described themselves as just about right in terms of weight had 0.25 subtracted from their ZBMI. The ZBMI of those who placed themselves in the slightly overweight category decreased by 1.18, whereas it decreased by 1.78 for those falling into the very overweight self-description category to obtain WSI. Thus, a low number means that an individual is thinner than the average person with the same body weight self-rating. In this construction of body satisfaction, a low number indicates dissatisfaction with body weight. A high number indicates a person heavier than the average Body Satisfaction 21 person who gave a particular body weight rating, and thus has relative body satisfaction. Such manipulations were done to compare weight perception while taking into account ZBMI, and thus better measure body satisfaction. Design We obtained the YRBSS data for this correlational observation study. The study design is repeated cross-sections of American high school students in years 1999, 2001, 2003, 2005, and 2007. Self-report data in the form of survey responses from different students was used to analyze the relationships between demographics, attitudes, and self-reported behaviors related to body dissatisfaction and weight control behaviors. Data Preparation The cleaned data sets were downloaded from the CDC website and analyzed to determine consistent variables over the years of interest. The years to be studied were selected based on the data they provided in relation to the research questions. The five selected datasets were merged into one large dataset and checked again for errors. Coding of variables, such as labeling unnamed variables in the data sets for years 2001 and 2003, simplified data analysis. Furthermore, recoding of any divergent variables made the variables of interest consistent across the years. For instance, the Hispanic and Latino categories in the year 2007 data for the ethnicity variable were merged into one category to better coincide with earlier data. Data Analysis Finally the data was analyzed. SPSS, a computer program, was used to perform descriptive statistics on sample characteristics (demographic variables) and key variables to assess participant attitudes and behavior by year. All SPSS analyses used the case weights. Body Satisfaction 22 Secondly, multivariate hypothesis testing was performed with AM Statistical Software on variables that measure body dissatisfaction and weight control behaviors. Use of AM Statistical Software yielded accurate estimates of variability rather than underestimates of variability due to created correlated errors within clustered sampling units (Bell-Ellison & Kromrey, 2007). Such statistical programs that yield accurate estimates of variability and incorporate sample weights lead to appropriate analysis using complex data from sample surveys. Each hypothesis was examined with hierarchical regression analysis. For instance, to analyze change in body satisfaction over time, linear regressions were done first with ethnicity, gender, and grade variables to control for demographic variables and then the year variable was added to the equation to test the first hypotheses via the change in R-squared. Beta weights were also analyzed to determine whether the relationship was positive or negative. Body Satisfaction 23 Results Sample Description The demographics were relatively comparable across the sampled data. The distribution of the demographic variables (see Table 3) was similar to the distribution of the key variables (see Table 4). The year 1999 has the most data, but all years have a relatively similar and sufficient amount of data to address the research questions. Body mass index remained fairly constant across the years with a very slight increase, so it should not have confounded the data. While the collected data concentrated on students from ages 15 to 17, it was fairly evenly distributed across 9th through 12th grade. The trends also remained constant across the 8 years. Additionally, the sampling of males and females remained at a roughly 1:1 ratio across all 8 years, so gender should not have confounded the results either. However, a larger amount of people identifying themselves as other or mixed ethnicity (15.6%) was sampled in 1999 compared to the other years. If ethnicity has a strong influence on body dissatisfaction and eating disorder related behavior, then this might have confounded results based on trends over time. However, weighting likely reduced potential confounding. Furthermore, heavy sampling from minority populations enabled the answering of questions related to ethnicity, and was therefore desirable. Ultimately, the size and distribution of the data appears to be robust enough to address the research questions. Table 3 presents the frequency and percent of collected data for each studied year according to demographic variables. The mean and standard deviation were given for the body mass index and WSI variables, because they are continuous variables. Body Satisfaction 24 Table 3 Frequency & Percent of Collected Data for Demographic Variables by Year 1999 Variable BMI WSI 2001 Year 2003 2005 2007 Age <12 13 14 15 16 17 > 17 Total M 23.02 -0.078 Freq. 1 10 1347 3532 4027 3452 2062 14431 SD 4.69 0.8169 % 0.0% 1.0% 9.3% 24.5% 27.9% 23.9% 14.3% M 22.85 -0.102 Freq. 2 11 1388 3186 3203 2948 1789 12527 SD 4.54 0.8168 % 0.0% 0.1% 11.1% 25.4% 25.6% 23.5% 14.3% M 23.19 -0.016 Freq. 5 6 1501 3371 3468 3130 1710 13191 SD 4.56 0.7994 % 0.0% 0.0% 11.4% 25.6% 26.3% 23.7% 13.0% M 23.43 -0.002 Freq. 3 13 1324 3433 3399 3071 1792 13035 SD 4.79 0.7919 % 0.0% 0.1% 10.2% 26.3% 26.1% 23.6% 13.7% M 23.42 0.016 Freq. 7 8 1405 3290 3316 3047 1743 12816 SD 4.76 0.7932 % 0.1% 0.1% 11.0% 25.7% 25.9% 23.8% 13.6% Grade 9th 10th 11th 12th Other Total 4023 3743 3446 3167 7 14386 28.0% 26.0% 24.0% 22.0% 0.0% 3732 3144 2855 2756 7 12494 29.9% 25.2% 22.9% 22.1% 0.1% 3729 3508 3113 2810 6 13166 28.3% 26.6% 23.6% 21.3% 0.0% 3694 3411 3052 2855 8 13020 28.4% 26.2% 23.4% 21.9% 0.1% 3609 3359 3032 2792 3 12795 28.2% 26.3% 23.7% 21.8% 0.0% 7383 7048 51.2% 48.8% 6094 6433 48.6% 51.4% 6801 6389 51.6% 48.4% 6595 6440 50.6% 49.4% 6507 6309 50.8% 49.2% 8765 1969 1440 2257 14431 60.7% 13.6% 10.0% 15.6% 8550 1526 1449 1002 12527 68.3% 12.2% 11.6% 8.0% 8078 1833 2215 1064 13190 61.2% 13.9% 16.8% 8.1% 8109 1841 1888 1197 13035 62.2% 14.1% 14.5% 9.2% 7776 1869 2070 1101 12816 60.7% 14.6% 16.2% 8.6% Gender Male Female Total Ethnicity White Black Hispanic Other Total Table 4 displays the key variables and the frequency and percent of the data for each year. As can be seen in Table 4, while 1999 has slightly more data than the following years, all the years have enough data points to find significant differences between the years. The rate of self-descriptions of underweight appears to slightly decrease over the years. Although some of the percentages of weight control behaviors are relatively small, the amount of data is still high enough to make meaningful conclusions. For instance, only 4.4% of the students reported purging in 2007, but the data frequency of 607 is substantive enough to address research Body Satisfaction 25 questions. Overall the data are fairly consistent and well distributed over the 8 years, despite a few trends over the years in the data. Ultimately, there is enough data for all variables across all 8 years to warrant their study. Body Satisfaction 26 2005 2007 Table 4 Frequency & Percent of Collected Data for Key Variables by Year 1999 Variable Describe Weight Freq. Very Under Slightly Under About Right Slightly Over Very Over Total Year 2003 2001 % Freq. % Freq. % Freq. % Freq. % 398 2.6% 343 2.6% 379 2.6% 278 2.0% 272 2.0% 2136 14.0% 1771 13.2% 1967 13.3% 1661 12.1% 1599 11.6% 8201 53.7% 7302 25.8% 8059 54.6% 7498 54.5% 7769 56.3% 3866 25.3% 3464 25.8% 3714 25.2% 3688 26.8% 3542 25.7% 657 15258 4.3% 566 13446 4.2% 629 14748 4.3% 630 13755 4.6% 612 13794 4.4% Present Absent Total 8640 6554 15194 56.9% 43.1% 7776 5650 13426 57.9% 42.1% 8415 6511 14926 56.4% 43.6% 8254 5473 13727 60.1% 39.9% 8288 5431 13719 60.4% 39.6% Present Absent Total 5904 9263 15167 38.9% 61.1% 5548 7768 13316 41.7% 58.3% 5945 8799 14744 40.3% 59.7% 5538 8179 13717 40.4% 59.6% 5455 8279 13734 39.7% 60.3% Present Absent Total 1850 13368 15218 12.2% 87.8% 1750 11567 13317 13.1% 86.9% 1898 12856 14754 12.9% 87.1% 1659 11638 13297 12.5% 87.5% 1597 11636 13233 12.1% 87.9% Present Absent Total 1071 14127 15198 7.0% 93.0% 1215 12236 13451 9.0% 91.0% 1246 13576 14822 8.4% 91.6% 862 12877 13739 6.3% 93.7% 793 12542 13335 5.9% 94.1% Present Absent Total 714 14474 15188 4.7% 95.3% 714 12699 13413 5.3% 94.7% 857 13940 14797 5.8% 94.2% 639 13053 13692 4.7% 95.3% 607 13128 13735 4.4% 95.6% Exercise Diet Fast Pills Purge Models Hierarchical linear regression and beta weights were used to test the six hypotheses. The first table for each hypothesis test displays the hierarchical regression analysis (with the variables added to the regression equation in the first column and the subsample size (n) in the next). The coefficient of alienation is “k,” and “F” tests for the significance of the hypothesis that R2 change Body Satisfaction 27 is equal to 0. (The program only provides R2 to 3 decimal places.) For each hypothesis test, two analyses were done. First, a regression was done using the control variables. Then the variable critical to the hypothesis test was added. From the two R2 values, we computed R2 change and used Excel to calculate the significance of R2 change. Change Over Time Hypothesis one: increase in body dissatisfaction over time. Tables 5 and 6 show results for the hypothesis that body dissatisfaction will increase over time. As can be seen in Table 5, when race, grade, gender, and ZBMI were controlled, the year added no contribution to the regression equation for WSI. The R2 change value was 0.00000. Table 5 Weight Satisfaction Index Over Time Model Race, grade, gender ZBMI Year n R2 k 64,000 64,000 64,000 5 7 8 R2 change 0.083 0.674 0.674 F -0.59100 0.00000 p -56110.80267 0.00000 -0.0000 1.0000 Table 6 shows a slight increase in WSI over time (p<0.006). Hypothesis one is not supported since there was a small, but significant, improvement in body satisfaction over time. Table 6 Weight Satisfaction Index Over Time Parameter Name Constant White Black Hispanic Sex Grade ZBMI Year MSE Estimate SE -0.669 0.015 0.172 0.030 0.254 -0.019 0.626 0.003 0.211 t 0.016 0.011 0.012 0.013 0.006 0.003 0.004 0.001 -- p > |t| -42.643 1.386 13.926 2.349 40.716 -7.643 172.078 2.756 -- 0.000 0.167 0.000 0.020 0.000 0.000 0.000 0.006 -- Body Satisfaction 28 Hypothesis two: decrease in healthy behaviors & increase in extreme behaviors over time. Results of the hypothesis that healthy food consumption would decrease over time are displayed in Tables 7 and 8. This hypothesis failed to be confirmed with an R2 change of 0.00000 when year was added to the regression equation (see Table 7). Table 7 Healthy Food Consumption Over Time Model Ethnicity, gender, grade ZBMI Year n R2 k 64,000 64,000 64,000 4 5 7 R2 change 0.013 0.013 0.013 -0.00000 0.00000 F p -0.00000 0.00000 -1.0000 1.0000 Table 8 indicates a slight decrease in consumption of healthy food over time (p>0.014) in accordance with the hypothesis. However, the small R2 change value shows that support for this hypothesis is weak. Table 8 Healthy Food Consumption Over Time Parameter Name Constant Black Hispanic Other Ethnicity Grade Gender ZBMI Year MSE Estimate SE -0.031 -0.259 -0.091 0.069 -0.016 0.115 0.005 -0.009 0.991 t 0.028 0.018 0.021 0.026 0.006 0.013 0.006 0.004 -- p > |t| -1.116 -14.679 -4.402 2.631 -2.846 9.129 0.857 -2.469 -- 0.266 0.000 0.000 0.009 0.005 0.000 0.393 0.014 -- Tables 9 and 10 show results for extreme weight control variables. R2 was significant, but small, 0.1% of the variance. Body Satisfaction 29 Table 9 Extreme Weight Control Behaviors Over Time Model Ethnicity, gender, grade ZBMI Year n k 64,000 64,000 64,000 R2 4 0.033 5 0.042 6 0.043 R2 change F -0.00900 0.00100 p -13712.78571 1488.18605 -0.0000 0.0000 As can be seen in Table 10, there was a slight decrease in extreme weight control behaviors from 1999 to 2007, which disconfirms predictions (p>0.005). Table 10 Extreme Weight Control Behaviors Over Time Parameter Name Constant Black Hispanic Other Ethnicity Grade Gender ZBMI Year MSE Estimate SE 0.470 -0.034 0.037 0.028 0.021 -0.383 0.098 -0.010 0.975 t 0.032 0.017 0.020 0.028 0.005 0.014 0.006 0.004 -- 14.725 -2.064 1.856 1.024 3.868 -27.849 15.619 -2.837 -- p > |t| 0.000 0.040 0.065 0.307 0.000 0.000 0.000 0.005 -- Tables 11 and 12 display results for the hypothesis that moderate weight loss strategies will decrease over time. Disconfirming the hypothesis, Table 11 shows that the year variable contributed nothing (R2=0.00000) to the regression equation. Table 11 Exercise & Diet Over Time Model Ethnicity, gender, grade ZBMI Year n k 64,000 64,000 64,000 R2 4 0.068 5 0.164 6 0.164 R2 change -0.09600 0.00000 F p -37459.31707 0.00000 -0.0000 1.0000 Table 12 shows no significant decrease in exercise and diet behavior over time (p>0.761). This fails to confirm the second hypothesis that healthy weight control behaviors would decrease Body Satisfaction 30 over time. Ultimately, there is little support for the second hypothesis. Weight control variables were fairly stable over time. Table 12 Exercise & Diet Over Time Parameter Name Constant Black Hispanic Other Ethnicity Grade Gender ZBMI Year MSE Estimate SE 0.830 -0.383 -0.077 -0.051 -0.015 -0.546 0.317 -0.001 0.845 t p > |t| 0.031 0.018 0.017 0.025 0.006 0.014 0.006 0.003 -- 27.191 -21.105 -4.517 -2.033 -2.419 -39.002 56.072 -0.305 -- 0.000 0.000 0.000 0.043 0.016 0.000 0.000 0.761 -- Gender and Ethnicity Differences Hypothesis three: greater body dissatisfaction and weight control behaviors among females. Tables 13 and 14 show results of the prediction that females will have higher rates of body dissatisfaction than males. As seen in Table 13, gender aided in predicting WSI (R2=0.02400), in accordance with expected results. Table 13 WSI by Gender Model Ethnicity, grade ZBMI Year Gender n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.028 0.649 0.650 0.674 -0.62100 0.00100 0.02400 F p -61232.13097 98.44769 2278.57567 -0.0000 0.0000 0.0000 As predicted, Table 14 indicates greater weight satisfaction among males than females (p>0.006). Body Satisfaction 31 Table 14 WSI by Gender Parameter Name Constant Black Hispanic Other Ethnicity Grade ZBMI Year Gender MSE Estimate SE -0.654 0.157 0.015 -0.015 -0.019 0.626 0.003 0.254 0.211 t p > |t| 0.013 0.008 0.013 0.011 0.003 0.004 0.001 0.006 -- -50.435 19.994 1.174 -1.386 -7.643 172.078 2.756 40.716 -- 0.000 0.000 0.242 0.167 0.000 0.000 0.006 0.000 -- Tables 15 and 16 show results of the hypothesis that females will more frequently consume healthy foods than males. Gender slightly contributed (R2 change=0.013) to the regression equation (Table 15). Table 15 Healthy Food Intake by Gender Model Ethnicity, grade ZBMI Year Gender n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.009 0.009 0.010 0.013 -0.00000 0.00100 0.00300 F p -0.00000 6399.10000 14766.92308 -1.0000 0.0000 0.0000 In contrast to predictions, Table 16 shows that males more frequently consumed healthy foods on a weekly basis than females (p>0.000). These results disconfirm the hypothesis that females more frequently engage in weight control behaviors than males. Body Satisfaction 32 Table 16 Healthy Food Intake by Gender Parameter Name Constant Black Hispanic Other Ethnicity Grade ZBMI Year Gender MSE Estimate SE -0.031 -0.259 -0.091 0.069 -0.016 0.005 -0.009 0.115 0.991 t p > |t| 0.028 0.018 0.021 0.026 0.006 0.006 0.004 0.013 -- -1.116 -14.679 -4.402 2.631 -2.846 0.857 -2.469 9.129 -- 0.266 0.000 0.000 0.009 0.005 0.393 0.014 0.000 -- In Tables 17 and 18 the findings of the hypothesis that extreme weight control behaviors will be more common among females. Table 17 shows that gender contributed to the regression equation (R2 change=0.03600) while controlling for ethnicity, grade, and ZBMI. This supports the third hypothesis. Table 17 Extreme Weight Control Behaviors by Gender Model Ethnicity, grade ZBMI Year Gender n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.001 0.007 0.007 0.043 -0.00600 0.00000 0.03600 F p -54851.14286 0.00000 53573.02326 -0.0000 1.0000 0.0000 Table 18 confirms expected greater frequency of extreme weight control behaviors among females compared to males (p>0.000). Body Satisfaction 33 Table 18 Extreme Weight Control Behaviors by Gender Parameter Name Constant Black Hispanic Other Ethnicity Grade ZBMI Year Gender MSE Estimate SE 0.470 -0.034 0.037 0.028 0.021 0.098 -0.010 -0.383 0.975 t p > |t| 0.032 0.017 0.020 0.028 0.005 0.006 0.004 0.014 -- 14.725 -2.064 1.856 1.024 3.868 15.619 -2.837 -27.849 -- 0.000 0.040 0.065 0.307 0.000 0.000 0.005 0.000 -- Tables 19 and 20 show results for diet and exercise by gender. As expected, Table 19 indicates that gender contributed significantly to the regression equation for predicting diet and exercise, accounting for 7.3% of the variance. Table 19 Diet & Exercise by Gender Model Ethnicity, grade ZBMI Year Gender n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.010 0.091 0.091 0.164 -0.08100 0.00000 0.07300 F p -56960.80220 0.00000 28483.35366 -0.0000 1.0000 0.0000 As seen in Table 20, females also reported higher frequency of diet and exercise than males (p>0.000). This confirms the third hypothesis that greater rates of body dissatisfaction and weight control behaviors will be present among females than males. Body Satisfaction 34 Table 20 Diet & Exercise by Gender Parameter Name Constant Black Hispanic Other Ethnicity Grade ZBMI Year Gender MSE Estimate SE 0.830 -0.383 -0.077 -0.051 -0.015 0.317 -0.001 -0.546 0.845 t p > |t| 0.031 0.018 0.017 0.025 0.006 0.006 0.003 0.014 -- 27.191 -21.105 -4.517 -2.033 -2.419 56.072 -0.305 -39.002 -- 0.000 0.000 0.000 0.043 0.016 0.000 0.761 0.000 -- Hypothesis four: greater body dissatisfaction and weight control behaviors among Caucasians. Tables 21 and 22 show results of the hypothesis that WSI will be greatest among Caucasians. With R2 change=0.00400, ethnicity adds to the predictive value of the regression equation in accordance with the hypothesis (as can be seen in Table 21). Table 21 WSI by Ethnicity Model Gender, grade ZBMI Year Ethnicity n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.060 0.670 0.670 0.674 0.61000 0.00000 0.00400 F p 58262.28358 0.00000 379.7626113 0.0000 1.0000 0.0000 Table 22 shows that students identifying themselves as black tend to have greater body satisfaction than those identifying themselves as white (p>0.000). This confirms the hypothesis. However, when white students were compared to Hispanic students and those of other ethnicities, no significant results were found to confirm the hypothesis that higher body dissatisfaction would be present among white students. Body Satisfaction 35 Table 22 WSI by Ethnicity Parameter Name Constant Gender Grade ZBMI Year Black Hispanic Other Ethnicity MSE Estimate SE -0.654 0.254 -0.019 0.626 0.003 0.157 0.015 -0.015 0.211 t p > |t| 0.013 0.006 0.003 0.004 0.001 0.008 0.013 0.011 -- -50.435 40.716 -7.643 172.078 2.756 19.994 1.174 -1.386 -- 0.000 0.000 0.000 0.000 0.006 0.000 0.242 0.167 -- Tables 23 and 24 show healthy food intake by ethnicity. Ethnicity slightly added to the regression equation for healthy food intake with R2 change=0.00800 (Table 23), which supports the hypothesis that healthy food intake will be greater among Caucasians than other ethnicities. Table 23 Healthy Food Intake by Ethnicity Model Gender, grade ZBMI Year Ethnicity n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.004 0.004 0.005 0.013 -0.00000 0.00100 0.00800 F p -0.00000 12798.20000 39378.46154 -1.0000 0.0000 0.0000 Table 24 shows that compared to white students, black and Hispanic students were less likely to eat healthy food in support of the hypothesis (p>0.000). In contrast to the hypothesis, students of other ethnicities were more likely to eat healthy food (p>0.009). Thus, support for the hypothesis is weak at best. Body Satisfaction 36 Table 24 Healthy Food Intake by Ethnicity Parameter Name Constant Gender Grade ZBMI Year Black Hispanic Other Ethnicity MSE Estimate SE -0.031 0.115 -0.016 0.005 -0.009 -0.259 -0.091 0.069 0.991 t p > |t| 0.028 0.013 0.006 0.006 0.004 0.018 0.021 0.026 -- -1.116 9.129 -2.846 0.857 -2.469 -14.679 -4.402 2.631 -- 0.266 0.000 0.005 0.393 0.014 0.000 0.000 0.009 -- Tables 25 and 26 display results of the hypothesis that extreme weight control behaviors are most prevalent among Caucasians. Disconfirming the hypothesis, Table 25 shows that ethnicity added no significant contribution to predicting extreme weight control behaviors (R2 change=0.00000). Table 25 Extreme Weight Control Behavior by Ethnicity Model Gender, grade ZBMI Year Ethnicity n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.033 0.042 0.043 0.043 -0.00900 0.00100 0.00000 F p -13712.78571 1488.16279 0.00000 -0.0000 0.0000 1.0000 However, white students were more likely to engage in extreme weight control behaviors (p>0.040), as seen in Table 26. This offers very weak support for the fourth hypothesis. Additionally, results for other minorities were not statistically significant. Body Satisfaction 37 Table 26 Extreme Weight Control Behavior by Ethnicity Parameter Name Constant Gender Grade ZBMI Year Black Hispanic Other Ethnicity MSE Estimate SE 0.470 -0.383 0.021 0.098 -0.010 -0.034 0.037 0.028 0.975 t p > |t| 0.032 0.014 0.005 0.006 0.004 0.017 0.020 0.028 -- 14.725 -27.849 3.868 15.619 -2.837 -2.064 1.856 1.024 -- 0.000 0.000 0.000 0.000 0.005 0.040 0.065 0.307 -- Tables 27 and 28 show results for moderate weight control behaviors by gender. As seen in Table 27, the R2 change for ethnicity was 0.01600. This supports the hypothesis that Caucasians are more likely to engage in weight control behaviors than other ethnicities. Table 27 Diet & Exercise by Ethnicity Model Gender, grade ZBMI Year Ethnicity n R2 k 64,000 64,000 64,000 64,000 4 5 7 8 R2 change 0.058 0.148 0.148 0.164 -0.09000 0.00000 0.01600 F p -38914.66216 0.00000 6242.926829 -0.0000 1.0000 0.0000 Table 28 indicates that white students were more likely to diet and exercise than black students (p>0.000), Hispanic students (p>0.000), and students of other ethnicities (p>0.043). This confirms the hypothesis that diet and exercise behaviors are greatest among white students. Body Satisfaction 38 Table 28 Diet & Exercise by Ethnicity Parameter Name Constant Gender Grade ZBMI Year Black Hispanic Other Ethnicity MSE Estimate SE t 0.830 -0.546 -0.015 0.317 -0.001 -0.383 -0.077 -0.051 0.845 p > |t| 0.031 0.014 0.006 0.006 0.003 0.018 0.017 0.025 -- 27.191 -39.002 -2.419 56.072 -0.305 -21.105 -4.517 -2.033 -- 0.000 0.000 0.016 0.000 0.761 0.000 0.000 0.043 -- Relationship between Body Dissatisfaction and Weight Control Behavior Hypothesis five: positive association between body dissatisfaction and weight control behaviors. Tables 29 and 30 show the relationship between WSI and weight control behaviors. Given that R2 change=0.0000 with the addition of the year variable to the regression equation, as seen in Table 29, it appears that the relationship between WSI and weight control behaviors was stable over time. Table 29 also indicates the presence of a relationship between WSI and weight control behaviors (R2 change=0.01700). This supports the hypothesis that as body dissatisfaction increases weight control behaviors will also increase. Table 29 Relationship between WSI & Weight Control Behaviors Model Ethnicity, gender, grade ZBMI Year Weight Control n R2 k 64,000 64,000 64,000 64,000 5 7 8 13 0.083 0.674 0.674 0.6910 R2 change -0.59100 0.00000 0.01700 F p -56110.80267 0.00000 1574.16064 -0.0000 1.0000 0.0000 Body Satisfaction 39 As seen in Table 30, there is a positive association between WSI and healthy food intake in contrast to prediction (p>0.026). Table 30 also shows a negative association between extreme weight control behaviors and diet and exercise as expected (p>0.000). Table 30 Relationship between WSI & Weight Control Behaviors Parameter Name Constant Black Hispanic Other Ethnicity Gender Grade ZBMI Year Healthy Food Intake Extreme Weight Control Diet & Exercise MSE Estimate SE t -0.550 0.014 0.124 0.008 0.001 0.009 -0.019 0.011 0.181 0.007 -0.020 0.003 0.660 0.004 0.003 0.001 0.007 0.003 -0.054 0.005 -0.096 0.004 0.199 -- -40.284 15.401 0.162 -1.733 26.209 -7.831 161.120 2.379 2.240 -11.893 -23.683 -- p > |t| 0.000 0.000 0.871 0.084 0.000 0.000 0.000 0.018 0.026 0.000 0.000 -- Hypothesis six: greater prevalence of body dissatisfaction and weight control behaviors among older adolescents. Tables 31 and 32 show results for the hypothesis that body dissatisfaction will be greater among older adolescents than younger adolescents. As seen in Table 31, age accounted slightly for WSI (R2 change=0.00100), which confirms the hypothesis. Table 31 WSI by Age Model Ethnicity, gender ZBMI Year Age n R2 k 64,000 64,000 64,000 64,000 4 6 7 8 R2 change 0.078 0.673 0.674 0.675 -0.59500 0.00100 0.00100 F p -56575.39376 94.94214 94.80000 -0.0000 0.0000 0.0000 When the beta weights displayed in Table 32 are taken into account, a negative association between WSI and age seems apparent (p>0.000). Given the small R2 change value, Body Satisfaction this offers little support to the hypothesis that weight dissatisfaction is greater among older adolescents. Table 32 WSI by Age Parameter Name Constant Black Hispanic Other Ethnicity Gender ZBMI Year Age MSE Estimate SE -0.587 0.158 0.015 -0.016 0.257 0.626 0.003 -0.023 0.211 t p > |t| 0.016 0.008 0.013 0.011 0.006 0.004 0.001 0.002 -- -36.847 20.241 1.181 -1.461 41.561 171.562 2.570 -10.148 -- 0.000 0.000 0.239 0.145 0.000 0.000 0.011 0.000 -- Tables 33 and 34 show results of the hypothesis that healthy food intake increases with age. In contrast to prediction, Table 33 shows that age did not contribute to the regression equation for healthy food intake (R2 change=0.00000). Table 33 Healthy Food Intake by Age Model Ethnicity, gender ZBMI Year Age n R2 k 64,000 64,000 64,000 64,000 4 6 7 8 R2 change 0.012 0.012 0.013 0.013 -0.00000 0.00100 0.00000 F p -0.00000 4922.384615 0.00000 -1.0000 0.0000 1.0000 Table 34 shows no statistically significant relationship between age and healthy food intake (p>0.81). This fails to support the hypothesis. 40 Body Satisfaction 41 Table 34 Healthy Food Intake by Age Parameter Name Constant Black Hispanic Other Ethnicity Gender ZBMI Year Age MSE Estimate SE -0.025 -0.258 -0.089 0.070 0.116 0.006 -0.009 -0.009 0.991 t p > |t| 0.036 0.018 0.021 0.026 0.013 0.006 0.004 0.005 -- -0.704 -14.641 -4.286 2.696 9.154 0.877 -2.430 -1.755 -- 0.482 0 0 0.008 0.000 0.381 0.016 0.081 -- Tables 35 and 36 show extreme weight control variables by age. Table 35 indicates a slight contribution (R2 change=0.00200) of age to predicting extreme weight control behaviors, which supports the sixth hypothesis. Table 35 Extreme Weight Control Behaviors by Age Model Ethnicity, gender ZBMI Year Age n R2 k 64,000 64,000 64,000 64,000 4 6 7 8 R2 change 0.033 0.042 0.042 0.044 -0.00900 0.00000 0.00200 F p -13712.5714 0.00000 2908.63636 -0.0000 1.0000 0.0000 Table 36 shows that as age increased, the frequency of students using extreme weight control behaviors increased (p>0.0000). This confirms the hypothesis that extreme weight control behaviors will increase with age. Body Satisfaction Table 36 Extreme Weight Control Behaviors by Age Parameter Name Constant Black Hispanic Other Ethnicity Gender ZBMI Year Age MSE Estimate SE 0.350 -0.035 0.039 0.029 -0.387 0.099 -0.010 0.035 0.974 t p > |t| 0.040 0.017 0.020 0.027 0.014 0.006 0.004 0.005 -- 8.661 -2.134 1.955 1.049 -28.271 16.033 -2.777 6.682 -- 0.000 0.034 0.052 0.295 0.000 0.000 0.006 0.000 -- Tables 37 and 38 show results of the hypothesis that rates of diet and exercise are positively associated with age. As seen in Table 37, age did not significantly contribute to predicting diet and exercise (R2 change =0.00000). This disconfirms the hypothesis. Table 37 Diet & Exercise by Age Model Ethnicity, gender ZBMI Year Age n R2 k 64,000 64,000 64,000 64,000 4 6 7 8 R2 change 0.066 0.164 0.164 0.164 -0.09800 0.00000 0.00000 F p -38239.12195 0.000 0.000 -0.0000 1.0000 0.0000 Disconfirming the hypothesis, Table 38 shows that younger adolescents appear to diet and exercise slightly more than older adolescents (p>0.001). 42 Body Satisfaction Table 38 Effect of Age on Diet & Exercise Parameter Name Constant Black Hispanic Other Ethnicity Gender ZBMI Year Age MSE Estimate SE 0.881 -0.381 -0.076 -0.050 -0.544 0.316 -0.001 -0.018 0.845 t 0.037 0.018 0.017 0.024 0.014 0.006 0.003 0.005 -- p > |t| 23.926 -21.052 -4.496 -2.050 -39.010 55.849 -0.338 -3.320 -- 0.000 0.000 0.000 0.042 0.000 0.000 0.736 0.001 -- 43 Body Satisfaction 44 Discussion Major Findings Table 39 offers an overview of the results from each hypothesis. After the hypothesis is stated in the second column, the level to which significant results confirm or disconfirm the hypothesis is presented to the right. Finally, a brief conclusion is shown that corresponds to each hypothesis. Table 39 Overview of Majors Findings Number 1 Hypothesis Increase in BD over time Degree of Support Slight increase in WSI over time 2 Decrease in healthy behaviors and increase in unhealthy behaviors over time 3 Greater BD and WCB among females 4 Greater BD and WCB among Caucasians 5 Positive association between BD and WCB 6 Greater BD and WCB among older adolescents Slight decrease in healthy food intake over time, slight decrease in extreme WCB over time, and no significant decrease in moderate weight loss strategies over time Greater BD, extreme WCB, and weight loss strategies among females, but greater healthy food intake among males Slightly greater BD among white students than black students, very weak support for white students engaging in extreme WCB more than black students, and slightly greater incidence of diet and exercise among white students Slight negative relationship between BD and healthy food intake contrasts with positive relationship between BD extreme WCB, diet, and exercise Slightly greater BD and extreme WCB among older adolescents offers little support, which contrasts with very slightly greater diet and exercise among younger adolescents Conclusion BD appears fairly stable from 1999 to 2007 WCB appear fairly stable from 1999 to 2007 Presence of BD and behaviors explicitly targeted at weight loss are more common among females BD and WCB may be slightly greater among white students when compared to black students BD appears to be positively associated with behaviors explicitly targeted at weight loss BD and WCB appear to be present at roughly similar rates among high school students of all ages Note. BD = body dissatisfaction; WCB = weight control behaviors. Over time there was a slight decrease in healthy food intake as predicted, however in contrast to predictions there was a slight increase in WSI and a slight decrease in extreme weight control behaviors over time. Effect sizes were extremely small (with time accounting for no Body Satisfaction 45 more than 0.1% of the variance of all the regression equations). Thus, body satisfaction and weight control behaviors appear fairly stable from 1999 to 2007. This converges with Cash, Morrow, Hrabosky, and Perry’s findings (2004) that body satisfaction improved among nonblack and black females in the mid-nineties and male body dissatisfaction was fairly stable from 1983 to 2001, as well as Rozin, Trachtenberg, & Cohen’s study (2001). In confirmation of hypothesis three, males tended to have a higher WSI than females who more frequently engaged in extreme weight control behaviors, diet, and exercise than males. These results are in accord with Dolan and colleagues' study (1987) and a study that found greater body dissatisfaction and weight loss measures among high school females (Paxton, S. J., et al., 1991). More males consumed healthy food than females in contrast to expectations, but consistent with another study (Neumark-Sztainer, D., et al., 2006). However, this result may reflect greater caloric intake among males (Rolls, Fedoroff, & Guthrie, 1991), rather than a higher ratio of healthy to unhealthy food intake. Black students appeared more satisfied with their body weight than white students, who more frequently engaged in weight control behaviors than black students as predicted. Such findings are consistent with previous literature that suggests greater prevalence of dieting (White, Kohlmaier, Varnado-Sullivan, & Williamson, 2003) and disordered eating behavior (StreigelMoore, et al., 2000) among white females than black females. These body satisfaction differences might also be interpreted as a reflection of black females’ apparent greater flexibility in construction of body image ideals (Parker, Nichter, Nichter, Vuckovic, Sims, & Ritenbaugh,1995), which may allow for greater accommodation of overweight bodies more common among black females (Yun et al., 2006). Body Satisfaction 46 Disconfirming the hypothesis that WSI is positively associated with weight control behaviors, a positive association between body satisfaction and healthy food consumption was found. However, a negative association between WSI and extreme weight control behaviors, diet, and exercise confirmed this hypothesis. Given these results, it seems probable that healthy food consumption (as indexed in this study) may not be usefully conceptualized as a weight control behavior. Perhaps black students’ tendency to eat less healthy food than white students is a result of socioeconomic disparities (Drewnowski, 2004), which are reflected in higher rates of adiposity (Shrewsbury & Wardle, 2008), rather than relatively greater body satisfaction. If this is the case, then this study’s results may be interpreted as consistent with findings of positive association between body dissatisfaction and weight control efforts (Stice & Shaw, 2002), (Killen et al., 1996). Finally, as expected, older adolescents were barely more likely to have a lower WSI and engage in extreme weight control behaviors. This converges with findings of consistent body image across grade (Talamayan, Springer, Kelder, Gorospe, & Joye, 2006), life span (Tiggemann, 2004), and age (Stevens & Tiggemann, 1988), as well as higher prevalence of selfreported disordered eating behaviors among older adolescent females (Jones, Bennett, Olmsted, Lawson, & Rodin, 2001). Yet, in contrast to the hypothesis that older adolescents would have higher rates of body dissatisfaction and weight control behaviors, younger adolescents dieted and exercised more than older adolescents. Limitations There are several limitations to this study. One of the biggest limitations is that it is solely based on collected survey data. This results in construction of ZBMI from adolescents’ selfreports, which have been shown to overestimate height and underestimate weight (Brener, Body Satisfaction 47 McManus, Lowry, & Wechsler, 2003). Second, the unconventional variable used to measure body satisfaction, WSI, has not been used or substantiated in other studies. The WSI variable also fails to take into account participants, such as prepubescent males, who may weigh less than their desired weight and experience body dissatisfaction due to perception of being underweight. This limits the confidence of conclusions in regard to body dissatisfaction that can be drawn from this study. Additionally, interaction effects were not included. Therefore, we might have missed an interaction between gender and ethnicity. Last, no “causal claims” can be made from the results of this study, as it lacks any experimental manipulation. Implications Most of the literature on trends in body dissatisfaction seem to indicate its growth over time, as indicated by a meta-analysis of 222 studies (Feingold & Mazzella, 1998). However, results from this study suggest relative constancy in body satisfaction, as well as weight control behaviors, among adolescents in more recent years. Perhaps body satisfaction, and accordingly weight control behaviors, has stabilized in recent years. While this might be taken as an indication of improvement in combating body dissatisfaction and eating pathology, their apparent firmness and staying power ought to also be stressed. Renewed effort to reduce body dissatisfaction and disordered eating is necessary. This study shows the prevalence of body dissatisfaction across ethnically and regionally diverse adolescents in the United States, providing a better understanding a representative sample of United States high school students. It also confirms previous findings that females and white people are at high risk for body dissatisfaction and extreme weight control behaviors. Additionally, greater prevalence of body dissatisfaction than extreme weight control behaviors among adolescents and the positive association between body dissatisfaction and Body Satisfaction 48 extreme weight control behaviors appear to be consistent with the conceptualization of body dissatisfaction as a potential precursor to eating pathology. Therefore, findings from this study might lend some support to a pathway model of the development of eating disorders in which body dissatisfaction is key (Stice & Shaw 2002). Finally, body dissatisfaction and weight control behaviors appear to present at roughly similar rates across high school students of different ages. This consistency may suggest that body dissatisfaction generally develops prior to the time that adolescents reach high school. Therefore, preventive interventions will likely be most effective when they are done before people reach adolescence. Future Research This study allows for several areas of improvement in future research. First, physical measurement of participant height and weight, rather than reliance on self-report, may reduce self-report error and improve the accuracy of body mass index. Measuring body dissatisfaction in multiple ways, such as the difference between actual weight and ideal weight, the degree of manipulation to transform an image of perceived body shape to an image of ideal body shape, and explicit report of satisfaction, would provide more compelling results. Experimental designs that manipulate body satisfaction may allow for causal claims about the relationship between body dissatisfaction and eating disorder behavior. Based on these findings, more research among populations at the age of onset of body dissatisfaction and disordered eating behaviors seems necessary. For instance, future research into body dissatisfaction in childhood may lead to greater understanding of the etiology of body dissatisfaction (Davison, Markey, & Birch, 2003). Ultimately, more quality research into the Body Satisfaction 49 mechanisms that may lead to disordered eating behavior, such as body dissatisfaction, will likely improve our understanding and ability to prevent eating pathology and weight problems. Body Satisfaction 50 References Agras, W. S. (2001). The consequences and costs of the eating disorders. Psychiatry Clinical North America, 24, 371-379. Anderson, L. A., Eyler, A. A., Galuska, D. A., Brown, D. R., & Brownson, R. C. (2002). 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