Graduate Student Journal of Psychology Copyright 2 Graduate Student Journal of Psychology Copyright 2007 by the Department of Counseling & Clinical Psychology 2007, Vol. 9 Teachers College, Columbia University ISSN 1088-4661 Adolescent Body Mass Index in Relation to Depression, Self-Esteem, and Academic Achievement Mathew Malter-Cohen Teachers College, Columbia University The differences in school achievement, depression, and self-esteem among overweight and normal weight adolescents were investigated. Body Mass Index (BMI), measured weight status, and group classification (overweight or normal weight) were determined by k-means cluster analysis. Multi- variate analyses of variance (MANOVA) indicated significant effects across weight classifications. Overweight adolescents had a significantly lower grade point average than their normal weight counterparts. However, differences between weight groups for depression and self-esteem were in- significant. The implications and possible causes for these differences and similarities are dis- cussed. Recent research has documented extensively the ad- verse effects of obesity on orthopedic, neurological, pulmo- nary, and gastroenterological health (Must & Strauss, 1999; Zametkin, Zoon, Klein, & Munson, 2004). Overweight (Body Mass Index ≥ 85th percentile for age and gender) and obese (Body Mass Index ≥ 95th percentile for age and gen- der) individuals are at increased risk for a number of ill- nesses, including hypertension, hyperlipidemia, osteoarthri- tis, and Type II Diabetes, to name a few (Flegal, Carroll, Kuczmarski, & Johnson, 1998). Obese children between the ages of 10 and 13 have a 70% chance of being obese adults (The Office of the Surgeon General website, 2006). Given these findings, it is quite alarming to see the rates of child- hood and adolescent obesity nearly triple in the USA, from 5.7% to 15.3%, between 1980 and 2000 (Ogden, 2002). These increases in childhood and adolescent obesity span age, gender, and ethnicity (Dietz & Gortmaker, 2001). While the health effects of the obesity epidemic in the United States have been examined in great detail (Dietz & Gortmaker, 2001; Flegal et al., 1998; Zametkin, Zoon, Klein, & Munson, 2004), not much attention has been di- rected toward other important effects, such as decreased school performance in children and adolescents, and the ramifications for professional life in adults. Obesity and School Achievement While the research on the relationship between obesity and school achievement has been sparse, it has also been varied in its parameters. Taras and Potts-Datema (2005) published a literature review examining 10 studies from the past 50 years coming from Brazil, China, Finland, Thailand, the United Kingdom and the United States of America (USA). Only four of these studies originated from within Correspondence concerning this article should be addressed to Mathew Malter-Cohen; e-mail: mhm2108@columbia.edu. the USA (Datar, Sturm, & Magnabosco, 2004; Falkner et al., 2001; Schwimmer, Burwinkle, & Varni, 2003; Ter- shakovic, Weller, & Gallagher, 1994), even though the obe- sity problem in the USA is more pronounced than in other countries. In China, for example, Li (1995) examined an evenly matched cohort (obese and normal weight) of 204 elementary school children and found that severely obese children had significantly lower intelligence quotient (IQ) scores on the Wechsler Intelligence Scale for Children (WISC) than controls. Campos, Sigulem, Moraes, Escrivao and Fisberg (1996) found that children ages 8-13 years with normal height/weight ratios had significantly better per- formance on the WISC than their obese counterparts. In Thailand, Mo-suwan, Lebel, Puetpaiboon and Junjana (1999) found that being overweight during adolescence (grades seven to nine) was associated with poor school per- formance. Furthermore, adolescents who were more over- weight were at greater risk for low GPA. Li (1995) found that obese children performed significantly lower in six of the eight categories examined: Chinese, arithmetic, foreign language, general knowledge, art, and gym. Defining obe- sity as greater than 120% of sex/height specific mean weight for age, Mikkila, Lahti-Koski, Pietinen, Virtanen and Rimpela (2003) found good school performance to be inversely associated with being obese for boys and girls in a cohort of over 60,000 Finnish adolescents, ages 14-16. Within the USA, Datar, Sturm and Magnabosco (2004) analyzed data from a nationally representative cohort of 11,192 first-time kindergartners from the Early Childhood Longitudinal Study (ECLS), a project funded by the United States Department of Education. The ECLS began follow- ing these children in 1998 and will follow them through twelfth grade in order to test hypotheses about the effects of a wide range of family, school, community and individual variables on children's development, early learning, and early performance in school. The overweight kindergarten- ers enrolled in the ECLS had significantly lower math and 10 OBESITY AND SCHOOL ACHIEVEMENT 11 reading test scores compared with the non-overweight chil- dren. However, once they included socioeconomic and be- havioral variables in their model, Datar’s group concluded that overweight status is a marker, and not a causal factor, of poor test scores (Datar et al. 2004). The Affective Component Clinical reports and other qualitative data seem to indi- cate that weight is linked to both depression and self- esteem. However, recent studies on adolescents concerning emotional health indicate that the data are not so clear-cut. Swallen, Reither, Haas and Meier (2005) found that while overweight and obese adolescents (ages 15-17) had signifi- cantly worse self-reported health than normal weight ado- lescents, no difference existed between the groups on measures of depression, self-esteem, and school/social functioning. Several other studies found no differences in self-esteem between obese children and adolescents and non-obese controls (Gortmaker et al., 1993; Renman, Eng- strom, Silfverdal, & Aman, 1999; Rumpel & Harris, 1994). Other studies indicate that obese children and adolescents have somewhat lower self-esteem than their normal weight counterparts (Manus & Killeen, 1995; Stradmeijer, Bosch, Koops, & Seidell, 2000; Strauss, 2000). Still others found a difference in self-esteem between obese and normal weight children and adolescent girls that was rendered insignificant once body image was controlled for (French, Perry, Leon, & Fulkerson, 1995; Pesa, Syre, & Jones, 2000). Similar problems of confounding variables arise when examining the relationship between obesity and depression. Sjoberg, Nilsson and Leppert (2005) concluded that there is a significant statistical association between adolescent obe- sity and depression, although it disappeared when shaming experiences, parental employment, and parental separation were controlled for. These findings were similar to those of Erickson, Robinson, Haydel and Killen (2000), although they were studying a cohort of children in the third grade. In girls, they found a modest association (r = 0.14, p < .01) between depressive symptoms and Body Mass Index (BMI), which dropped out after controlling for level of overweight concerns. Erickson et al. (2000) found no asso- ciation between depressive symptoms and BMI in boys. The objective of this study of eleventh graders, in the USA, was to build on prior evidence (Datar et al., 2004; Mikkila et al., 2003; Mo-suwan et al., 1999) that has sug- gested that there exists a negative relationship between BMI and school achievement. As BMI increases, school achievement, measured here by grade point average (GPA) is expected to decrease. Due to the conflicting evidence presented by the literature concerning the relationship be- tween BMI and depression, we do not expect to see a rela- tionship between BMI and depression (Sjoberg et al., 2005; Swallen et al., 2005; Erickson et al., 2000). Additionally, no relationship is expected between BMI and self-esteem (Swallen et al., 2005; Renman et al., 1999; Rumpel & Har- ris, 1994; Gortmaker et al., 1993). Current research efforts into the possible biological correlates of obesity that have an impact on cognition will be examined. Method Sample Participants in this study consisted of students in elev- enth grade attending a public high school in an affluent community in the Northeast. During the year 2000, the me- dian annual family income in this region was reported to be almost $102,000 (U.S. Census Bureau, 1999); the highest national median income ever recorded by the U.S. Census is $43,318 (DeNavas-Walt, Proctor, & Mills, 2004). The majority of students, 87.1%, were of European American background, 0.8% were African American, 5% were His- panic, 4.2% were Asian American, and 2.9% were of other ethnic backgrounds. With regard to gender of the students, 46.7% were female and 53.3% were male. This study was implemented as part of a school-based initiative that targeted positive youth development, and inclusion of students in the sample was based on passive consent procedures (i.e. students are automatically included and given the opportunity to opt-out at any point, before, during, or after the study). Given increasing anecdotal and media-based evidence of various problems in communities such as theirs, school administrators and parent representa- tives in this particular community had sought a rigorous assessment of the nature and extent of difficulties among their high school students. Following the development of a collaborative relationship between the local school district and a Columbia University researcher, Dr. Suniya Luthar (which ensued from a series of talks she gave for the com- munity), the survey was initiated. School administrators sent letters to the parents of all eleventh graders by U.S. mail that described the project, indicated that survey results would be presented only in aggregate form (with no infor- mation on individual children), and requested notification if they preferred that their children not participate. A second notice was mailed a few days before data collection, once again offering parents the option to refuse consent. On each of the two days of data collection, all students were also told that their participation was entirely voluntary. On com- pletion of data collection, questionnaires were scored with only participant numbers as identifiers. Most of these stu- dents had participated in similar data collections conducted by Dr. Luthar during the sixth through tenth grades. Of the 252 eleventh graders who participated, BMI data was avail- able for only 240 of the students; 12 students did not report their heights and weights. Measures Subjective Reports of Maladjustment Depressive symptoms. MALTER-COHEN 12 The Children’s Depression Inventory is a widely used 27-item, three-choice scale designed to measure depression for school-age children and adolescents (Kovacs, 1992). This measure has acceptable internal consistency as well as criterion and concurrent validity (Kovacs, 1992). Alpha coefficients of internal consistency in this sample were .82 and .84 for girls and boys, respectively. Self-Perception Profile for Adolescents. The global self-worth subscale from the Self- Perception Profile for Adolescents (Harter, 1988) was ad- ministered to tap each participant’s overall perception of his or her worth as a person. Item content examines the extent to which adolescents approve of themselves along four di- mensions: (a) social competence, (b) physical competence, (c) romantic appeal, and (d) friendship. For each item, two sentence stems were presented side by side, for example, “Some teenagers are often disappointed with themselves,” but “Other teenagers are pretty pleased with themselves.” Students were asked to decide which stem best described them and whether the statement was “sort of true” or “really true” for them. Questions are written in a “structured alter- native format” designed to reduce the tendency to give so- cially desirable responses (Harter, 1982). Harter (1988) reports good psychometric characteristics for these scales. Alpha coefficients of internal consistency in this sample were .96 and .89 for girls and boys, respectively. Objective Reports of Maladjustment Body mass index. BMI is a measure of the weight of a person scaled according to height. A frequent use of BMI is to assess how much an individual's body weight departs from what is normal for a person of his or her height. The weight excess or deficiency may, in part, be accounted for by body fat (adipose tissue) although other factors, such as muscularity, also affect BMI. As a rough guideline for adults, a BMI of less than 20 implies underweight, over 25 is overweight, and over 30 is obese. BMI is calculated by taking the weight of the individual in kilograms and dividing by the square of the height in meters. BMI for children age 2 to 20 is calculated just as it is for adults, but it is classified differently. A BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is overweight. Children with a BMI between the 85th and 95th percentile are considered to be at risk of becoming overweight. BMI categories are generally regarded as a satisfactory tool for measuring whether sedentary individuals are "underweight," "overweight," or "obese." It has been used by the World Health Organization as the standard for recording obesity statistics since the early 1980s. Additionally, Piertobelli et al. (1998) tested the hy- pothesis that in a healthy pediatric population, BMI is a valid measure of fatness (total body fat and percent of body weight as fat were estimated by dual energy x-ray absorpti- ometry). The measure is also independent of age for both sexes (Piertobelli et al., 1998). Research thus supports the use of BMI as a fatness measure in groups of children and adolescents. Goodman and Strauss (2000) found self-report of BMI by adolescents to be a reliable indicator of actual BMI; 96.2% of teens were correctly classified as obese based on self-reported height and weight measures. Procedure Data for each student were collected during two 45- minute class periods on two separate days, and testing of the adolescents was done in groups of 15 to 20. To guard against biases due to variability in reading proficiencies, a member of the research team read each questionnaire aloud, and students marked their responses accordingly. Question- naires were administered in the same order to all groups, with relatively structured, non-threatening measures admin- istered at the beginning and end of each session. Students reported height and weight data in the demographics sec- tion. On completion of data collection, money to support a pizza party was given to all participating classes. Following the data collection, GPA was obtained directly from school administrators. Results Complete data were obtained for 238 of the eleventh graders who were attending the school sampled; the school withheld GPA for two of the students for reasons unknown to the investigators. Means and standard deviations on all variables are presented in Table 1. A k-means cluster analy- sis was performed on BMI to create two groups with maxi- mum distance between group averages. Multivariate analy- ses of variance (MANOVA) indicated significant effects across weight classifications (Wilks’s λ = .959, p < .05). Individual t-tests showed a significant difference between Table 1 Descriptive Data on All Variables Weight Classification Normal (BMI = 21.09) (n = 208) Overweight (BMI = 29.48) (n = 28) M SD M SD F Grade Point Averagea 9.10b 1.94 7.88 2.07 9.604** Depression 7.51 5.45 8.03 5.63 0.225 Global Self Esteem 3.18 0.52 3.05 0.40 1.625 a GPA measured on a 12 point scale, 12=A, 9=B, 6=C, 3=D b Means are convertible to standard collegiate 4-point scale by dividing by 3; subsequent group means are 3.03 and 2.63, respectively. ** p < .01 OBESITY AND SCHOOL ACHIEVEMENT 13 classifications for GPA (F = 9.604, p < .01), but not for depression (F = .225, p = .636), or global self-esteem (F = 1.625, p = .204). Error variance of all dependent variables was equal across groups and homogeneity was not violated. Discussion This study replicates findings of a strong association between BMI and GPA (Mikkila et al., 2003; Mo-suwan et al., 1999), while also furthering hypotheses that BMI is not associated with depression (Erickson, 2000; Swallen, 2005) or self-esteem (Gortmaker, 1993; Renman et al., 1999; Rumpel & Harris, 1994). Normal weight adolescents had an average GPA of 3.03 (when grades were converted to a standard collegiate 4-point scale), in comparison to an aver- age GPA of 2.63 for the overweight group. Miller (1998) found that high school grades “have a strong and significant effect on earnings 9 years after high school for both men and women, with or without bachelor’s degrees,” even after controlling for SES, race/ethnicity, region of the country and public or private status of the high school. While it was beyond the scope of this study to examine why overweight students are performing worse in school than their normal weight counterparts, current research efforts in the field suggest that certain structural and chemical differences in the brain among overweight individuals adversely affect memory and cognitive functioning (Jeong, Nam, Son, Son and Cho, 2004; Pannacciulli et al, in press). Pannacciulli et al. (in press) examined associations between excess body fat and regional alterations in brain structure using voxel-based morphometry. In comparison with the group of lean subjects, the group of obese indi- viduals had significantly lower gray matter density in sev- eral regions in the brain. In general, gray matter can be un- derstood as the parts of the brain responsible for informa- tion processing. Pannacciulli et al. identified structural brain differences associated with obesity in several brain areas involved in the regulation of reward and behavioral control, two processes that, along with information process- ing, have a significant impact on learning. Jeong, Nam, Son, Son and Cho (2004) used measurements of BMI and waistline circumference to study a Korean sample of 467 adults over age 64. Waistline circumference was included to better identify those adults who were overweight due to excess body fat and not due to other causes such as greater muscle mass or enlarged skeletal structure. Poor cognition was strongly associated with obesity (BMI ≥ 25) in the presence of abdominal obesity. In Korea, a BMI ≥ 25 is defined as obese while a BMI of 23-25 is defined as over- weight. In individuals with normal waist circumference, poor cognition was negatively associated with being over- weight. Additionally, abdominal obesity interacted with BMI in its association with poorer cognition. In this elegant study, Jeong, Nam, Son, Son, and Cho (2004) were able to isolate the effects of abdominal obesity (i.e. excessive body fat) on cognition above and beyond having elevated BMI. Finally, several other studies have shown that insulin defi- ciency, acute hyperglycemia and poor glucose tolerance are associated with impaired memory and cognitive dysfunc- tion in the elderly (Craft, 2005; Stockhorst, de Fries, Stein- grueber, & Scherbaum, 2004; Sommerfield, Deary, & Frier, 2004; Convit, Wolf, Tarshish, & de Leon, 2003). These conditions are more prevalent in obese populations, and are a consequence of Type II diabetes, a weight-related disor- der. In addition to the biological effects on learning, cogni- tion and memory, there is a socio-cultural impact on stu- dent’s academic outcomes. Unfortunately, at present, there is a dearth of quantitative research on this matter (Puhl & Brownell, 2001). The only examination of this topic known to this author found that obese adolescents were signifi- cantly less likely than their normal weight counterparts to gain college admission, despite equivalent academic re- cords and application rates (Canning & Mayer, 1966). While there has been considerable attention directed to- wards the harassment of, and shame wrought upon, obese children and adolescents in the school setting (Neumark- Sztainer, Story, & Harris, 1999; National Education Asso- ciation, 1994; Crandall, 1994), no attention has been paid to the direct or indirect effect this has upon their grades. While other studies have found mixed results when examining the relationship between obesity and depression in adolescents (Sjoberg et al. 2005; Erickson et al., 2000), this study did not (p=.636). Richardson et al. (2003) con- ducted a study of New Zealand adolescents that may ex- plain why this is so, at least for girls. They found that girls with major depression in late adolescence were twice as likely to be obese at age 26. The heterogeneous etiology of depression and subsequent complex effects this disease has on an individual likely explains why this study found no relationship with obesity. While some depressed adoles- cents may be obese, others have not yet experienced the effects of depression on their bodies. In essence, they may be too young for depression to have had an effect on their weight. Many researchers use the global self-worth subscale from the Self-Perception Profile for Adolescents (Harter, 1988) as a valid measure of self-esteem (French et al, 1995; Strauss, 2000; Strodmeijer et al., 2000). While the four di- mensions tapped by this instrument (social competence; physical competence; romantic appeal; and friendship), are areas in which obese adolescents experience difficulty (Puhl & Brownell, 2001; Neumark-Sztainer et al., 1999), normal weight adolescents also experience difficulty in these areas. Put more succinctly, it is not surprising that in this study the relationship between self-esteem and obesity was not statistically significant (p=.204); self-esteem is an issue with which most, if not all, adolescents struggle. Limitations and Conclusion One limitation of this study is sample size. Weight classification groups are of unequal size, and the size of the MALTER-COHEN 14 overweight group (N=28) significantly impacts the power of this study to examine all possible risk factors of elevated BMI. In a study such as this one, power of .8 or greater is ideal (Cohen, 1988). While the power of individual t-tests examining differences in depression (.076), and self-esteem (.246) between weight class groups in this study is less than ideal, this discrepancy is not significantly meaningful in this case. Extrapolating to larger group samples, it is unlikely that greater power would alter statistical signifi- cance between weight group averages on the CDI because the distributions are homoscedastic. A similar pattern of insignificant group differences, homoscedasticity, and neg- ligible clinical differences is observed when examining the group differences in self-esteem. Sample size further limits the ability to examine path models that may indicate direc- tion of causality. The devastating effects of obesity have gained national attention in the United States and articles are written weekly documenting these effects. Studies examining the biological effects of obesity on cognition are a recent de- velopment. 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