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Nutrition knowledge and body-image satisfaction of female adolescents
Nutrition Knowledge and Body-Image Satisfaction of Female Adolescents ROBIN H. SEARLES,l R. DALE TERRY,l AND ROSAUE
J.
AMOS2
IDepartment of Food and Nutrition and 2Department of Home Economics Education, College of Home Economics, Iowa State University, Ames, Iowa 50011 ABSTRACT This study examined the relationship between body-image satisfaction and knowledge of nutrition concepts related to weight control among 138 adolescent females. We administered a questionnaire to females aged 14 to 16, and obtained height and weight measurements. Sixty percent of the participants expressed more satisfaction than dissatisfaction with their bodies. Body aspects that these subjects were most frequently dissatisfied with were weight, hips, thighs, and bottom. Taller girls were more satisfied with their height than shorter girls, and lighter-weight girls were more satisfied with their weight than heavier girls. We used a multiple-choice test to assess nutrition knowledge concepts relevant to weight control. In general, the subjects seemed to know how to lose weight (using principles of energy intake and expenditure) but lacked knowledge of safe and reasonable dieting practices. The participants' nutrition knowledge test scores tended to increase with an increase in the mothers' education and socioeconomic levels. We did not find a significant correlation between body-image satisfaction and nutrition knowledge. (JNE 18:000-000, 1986)
During adolescence there is an increased awareness of self, with special focus on weight and appearance. Consequently, adolescents often compare their bodies with culturally defined ideal physiques. Unfortunately, Western cultures idealize thinness for women (1), and few adolescent females possess physiques that match these standards. Because adolescents are sensitive about weight and appearance, they are keenly aware of ways in which their developing bodies do not measure up to the cultural ideals. Thus, most adolescent females are dissatisfied with their body images. Numerous studies have investigated body-image dissatisfaction among both normal adolescents and adolescents with eating disorders (2). Adolescent females' body-image dissatisfaction often manifests itself in efforts to lose weight by dieting (3-5). Furthermore, Dwyer et al. (3) reported that 17to 18-year-old females who had dieted had a higher level of nutrition knowledge related to weight control than nondieters. Because dissatisfaction with body image seems to be a major stimulus for dieting among adolescent females, we hypothesized that knowledge of weight-control concepts would increase with a decrease in body-image satisfaction. The purpose of this VOLUME 18 NUMBER 3
1986
study was to examine the relationship between bodyimage satisfaction and knowledge of nutrition concepts related to weight control among adolescent females.
METHODS
Instrument development. We designed a questionnaire to gather data concerning adolescents' bodyimage satisfaction and their knowledge of nutrition concepts related to weight control, and demographic information such as their parents' socioeconomic levels and the adolescents' birth dates, weights, and heights. The body-image and nutrition knowledge components of the instrument are described below. Body image is difficult to measure adequately, and many instruments have been devised. Each instrument measures a slightly different aspect of body selfperception. Because low levels of body-image satisfaction are associated with adolescent dieting practices, we selected Secord and Jourard's Body Cathexis Scale (6), which assesses satisfaction with body-image. The Body Cathexis Scale lists a series of 20 body parts or aspects. Using a Likert-type scale from 1 (very dissatisfied) to 5 (very satisfied), participants circled how satisfied they felt with each body part or aspect listed. Several researchers (7-9) have found the reliability of the Body Cathexis Scale acceptable. To measure knowledge of nutrition concepts relevant to weight control, we constructed a test consisting of 24 multiple-choice items in the content areas of energy and energy balance. While constructing the test, we addressed content validity by following a table of specifications and by writing items to measure the behavioral objectives identified for each concept. We limited behavioral objectives to the lower two levels of the cognitive domain, knowledge and comprehension, as defined by Bloom et al. (10). Additionally, in writing the test items, we followed Gronlund's (11) guidelines for multiple-choice item construction, and we provided three alternative responses for each item (12). Four university nutrition faculty reviewed the test for content-related validity. JOURNAL OF NUTRITION EDUCATION
123
Using 14 adolescent females, ages 14 to 16, we pilottested the questionnaire to determine the clarity of directions and items. To refine the nutrition knowledge test, we analyzed the items (as described in the data analysis section of this article), and we revised three items based on analysis results.
schools were combined. Frequencies and percentages were calculated, and Spearman's rho correlation coefficients were computed between major variables. The level of significance selected for statistical analysis was .05.
Sample selection and data collection. We invited adolescent girls ages 14 to 16, in grades 8 through 11, from six junior and senior high schools to participate in the study (Note 1). All the schools were located in rural communities. Based on availability, we chose schools to obtain participants from the southern, central, and northern sections of the state. Students who were willing to participate and had written parental permission were included in the study. The major reasons for nonparticipation were that students reportedly forgot to have the parental permission form signed prior to data collection or they did not wish to have body weight taken. Demographic differences between participants and nonparticipants were not measured. We collected data from 142 students during class time (with the permission of the classroom teachers) or during study hall. After completing the questionnaire, each student was privately weighed and measured for height. For participating in the study, students were given their height and weight data.
RESULTS AND DISCUSSION
Data analysis. We excluded data from 4 of the 142 junior high and high school students who participated in our study. One subject was eliminated because of her age', another because of pregnancy, and 2 because of diseases that potentially influence body-image satisfaction. The university's test and evaluation service analyzed the nutrition knowledge test. Statistical analyses included a Kuder-Richardson-20 (KR-20) estimate of reliability, and a mean, standard deviation, and variance based on correct responses. Indices of difficulty and discrimination were calculated for test items (11). Next, by using each parent's occupation and level of educational attainment, socioeconomic level was determined according to the calculations described by Hollingshead (13). The total body-image satisfaction scores were calculated by adding the numerical responses for each body part or aspect and dividing by the total number of responses (6). Finally, based on percentile values from the National Center for Health Statistics (NCHS) (14), heights were assigned heightfor-age percentiles, and weights were assigned weight-for-height-and -age percentiles. Additional statistical procedures were carried out using packaged computer programs (15, 16). Since significant differences between schools were not found using the Scheffe procedure, the data from all 124
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Description of the sample. The participants' ages were well distributed, with slightly more 15-year-olds (39.8%) than 14- (31.9%) or 16- (28.3%) year-olds. Anthropometric measurements indicated that participants in our study were somewhat taller and heavier than the 14- to 16-year-old female sample from which the NCHS percentiles were derived, with approximately 40% of the participants in our study above the 75th height-for-age percentile, and 27% above the 75th weight-for-height-and-age percentile. The socioeconomic classifications of the participants' parents were divided into five levels, and tended to cluster in the middle three levels. However, compared to the fathers' socioeconomic classifications, the mothers' socioeconomic classifications were skewed toward the lower levels. This is possibly due to the relatively low wages associated with many of the jobs held by the mothers. Body-image satisfaction. We calculated response frequencies for each of the 20 body aspects included in the body-image satisfaction scale. Body aspects that the participants were most frequently "very dissatisfied" with were weight, hips, thighs, and bottom, respectively. Body aspects that most frequently received "very satisfied" ratings were height, leg-length, hands, width of shoulders, and calves, respectively. Overall, the body aspects related to skeletal size were more satisfying than those related to body fat. No respondent's total body-image satisfaction score was below 1.50 or above 4.51, indicating lack of any total body-image scores at either the "very dissatisfied" or "very satisfied" end of the scale, respectively. Sixty percent of the respondents had scores above 3.00, indicating an overall degree of satisfaction. The mean total body-image satisfaction score for the girls in this study was 3.16. Similar mean scores have been reported for college women (6) and 11- to 19-year-old females (17). Nutrition knowledge. Table 1 lists the average percentage of correct responses to items measuring each objective evaluated by the nutrition knowledge test. Because the independence of each item on the test was not ascertained, the data in Table 1 represent a relative ranking of the participants' knowledge regarding each objective. The nutrition knowledge test contained 9 VOLUME 18
NUMBER 3
1986
Average percent of correct responses to itemsa measuring each objective evaluated by the nutrition knowledge test
Table 1.
Objectiveb,c
Mean Percent of Correct Responses for Items Measuring Objective
2.7
Recognize that excess energy is stored as body fat Recognize the source of kilocalories 1.2 1.4 Identify the nutrients that supply kilocalories 2.10 Recognize relative differences in energy expenditure required for various activities 2.11 Recognize how specific foods, based on their caloric content, can affect energy balance 2.6 Recognize that weight gain is a normal part of growth and development 1.5 Distinguish between high and low kilocalorie foods 1.1 Select the correct definition of a calorie 2.4 Recognize a reasonable number of kilocalories a teenage girl should consume on a weight-loss diet 2.9 Recognize the relationships among food intake, activity, and body weight 1.6 Identify foods that contain fat, carbohydrate, and protein 2.5 Identify a reasonable rate of weight loss Recognize that fat is more calorically 1.3 dense than carbohydrate and protein 2.3 Identify the range of kilocalories needed per 24 hours by the average teenage girl 2.8 Recognize that body fat is essential for health 2.1 Recognize the calorie deficit that produces a one-pound loss of body fat 2.2 Recognize that the resting body uses energy
83% 75 69 68 68 67 63 57 57 56 50 45 43 34 27 22 19
aSome objectives include the results (% of correct responses) from more than 1 item. bObjectives 1.1-1.9 measure an energy concept. CObjectives 2.1-2.9 measure an energy balance concept.
items that measured 6 objectives related to the concept of energy. With one exception, the average percentage of correct responses was 50% or greater for items measuring these objectives. Incorrect responses to the items measuring the objective of "recognizing that fat is more calorically dense than carbohydrate and protein" reflect the common misconception that carbohydrates are fattening, and the limited recognition that fat is calorically dense. VOLUME 18 NUMBER 3
1986
Fifteen items on the nutrition knowledge test measured objectives related to the concept of energy balance. The percentage of correct responses was low for items that measured knowledge of relatively technical aspects of energy balance, such as knowing the size of the calorie deficit that produces a one-pound loss of body fat, and knowing that the resting body uses energy. Knowledge of these kinds of facts may not be essential for successful dieting. However, fewer than half of the participants correctly answered items for 3 objectives that are more essential for safe weight loss. These objectives dealt with knowing how many kilocalories an average teenage girl requires per day, identifying a reasonable rate of weight loss, and recognizing that some body fat is essential for health. Because knowledge level of certain energy and energy balance topics appeared high, while knowledge level of others ofthese topics was quite low, future studies should attempt to find out where teens receive information about these topics. Whether the lack of correct information is a result of misinformation or lack of information is not known. Other researchers who have administered nutrition knowledge tests to groups of adolescents have measured selected aspects of energy and energy balance. Skinner and Woodburn (18), using a multiple-choice test format, studied the nutrition knowledge of 1,193 male and female teens. They reported that 45% of their sample incorrectly defined calories as "the amount of fat in foods." In our study, 40% of the sample defined calories as the fat content of food. But Skinner and Woodburn also report that only 15% of their sample knew the relative calorie content of selected foods. In contrast, 63% of the sample tested in our study correctly answered questions regarding the relative calorie content of foods, a percentage similar to that found by Dwyer et al. (19). They reported that 58% of the 722 ninth- to twelfth-grade girls in their study correctly responded to multiple-choice questions on the caloric value of foods. The mean score for the nutrition knowledge test used in this study was 13.24 of a possible 24, with a standard deviation of 3.07 and a range of 7 to 22. The standard error of measurement was 2.21 in raw scores. The criteria for evaluating the effectiveness of each test item were a difficulty index ranging from 30 to 70; a discrimination index >0.20 or, if > 0.40, with a standard deviation> 0.20; and distracters chosen by three or more respondents (11). Of the 24 items, 14 met all three criteria, and 10 met two. The KR-20 formula for calculating an estimate of the internal consistency of the test revealed a coefficient of 0.48. This value is relatively low according to Mehrens and Lehmann (20), who recommend a coefficient ~ 0.65 for tests involving groups of people. The most probable explanation for the relatively low interJOURNAL OF NUTRITION EDUCATION
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nal consistency lies in the length of the test. Had the test been longer than 24 items, we could have obtained a more reliable sampling of the content areas. In addition, the mean score of 13.24 out of 24 indicates that the participants found this test difficult. As a result, scores tended to cluster.
adolescent girls. However, we also found that teenage girls lacked knowledge about certain basic weight control principles. 0
Statistical correlations. Spearman's rho correlation coefficients were computed between body-image satisfaction scores, nutrition knowledge test scores, and descriptive variables. We had hypothesized that a significant, negative correlation would exist between body-image satisfaction scores and nutrition knowledge test scores, but we did not find a significant correlation. Thus, girls in this sample who had relatively low levels of body-image satisfaction did not have a better knowledge of nutrition concepts related to weight control than did their more satisfied counterparts. However, we did find significant correlations between other variables. The participants' nutrition knowledge test scores tended to increase with an increase in the mothers' educational levels (r = 0.18, P :5 .05) and the mothers' socioeconomic levels (r = 0.26, P :5 .01). Numerous studies with adults have reported that nutrition knowledge is positively correlated with education and income. The participants' body-image satisfaction scores were negatively correlated with their weight-forheight-and-age percentiles (r = -0.34, P :5 .01). These results indicate that, at a given height and age, lighter-weight girls tended to be more satisfied with their body image than were heavier girls. In addition, satisfaction with weight was negatively correlated with weight-for-height-and-age percentile (r = -0.51, P :5 .001), whereas satisfaction with height was positively correlated with height-for-age percentile (r = 0.50, P :5 .001). In this study, we did not find a statistically significant relationship between nutrition knowledge and weight-for-height-and-age. However, Dwyer et a1. (3) found that the heavier female adolescents were more dissatisfied with body image yet tended to know more about nutrition than their lighter-weight counterparts. This difference between the studies may be the result of using different nutrition knowledge tests, or it may be because our study used a smaller sample of adolescents than Dwyer et a1. (3). In our sample, 36 girls were above the 75th weight-for-height-and-age percentile, and only 15 were above the 90th percentile. Thus, the subsample of potentially obese girls was relatively small. Many variables likely have a bearing on the level of body-image satisfaction and nutrition knowledge of female adolescents. Dissatisfaction with their body image seems to be a primary reason for dieting among
Journal paper no. J-11969 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project no. 2663, a contributing project to North Central Regional Research project No. 173, and journal paper no. 357 of the Home Economics Research Institute, College of Home Economics, Iowa State University, Ames, Iowa. Based on a thesis submitted by Robin H. Searles in partial fulfillment of the requirements for the degree of Master of Science. The authors gratefully acknowledge the cooperation of school systems in Iowa that participated in this project.
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ACKNOWLEDGMENT
NOTE The Iowa State University Committee on the Use of Human Subjects in Research approved the instrument and research procedures.
LITERATURE CITED 1 Garner, D. M., P. E. Garfinkel, D. Schwartz, and M. Thompson. Cultural expectations of thinness in women. Psychological Reports 47:483-91, 1980. 2 Garner, D. M., and P. E. Garfinkel, eds. Handbook of psychotherapy for anorexia nervosa and bulimia, New York: Guilford Press, 1985, 592 pp. 3 Dwyer, J. T., J. J. Feldman, and J. Mayer. Adolescent dieters: Who are they? American Journal of Clinical Nutrition 20:1045-56, 1967. 4 Dwyer, J. T., J. J. Feldman, C. C. Seltzer, and J. Mayer. Adolescent attitudes toward weight and appearance. Journal of Nutrition Education 1:14-19, 1969. 5 Kaufmann, N. A., R. Poznanski, and K. Guggenheim. Teenagers dieting for weight control. Nutrition and Metabolism 16:30-37,1974. 6 Secord, P. F., and S. M. Jourard. The appraisal of body cathexis and the self. Journal of Consulting Psychology 17:343-47,1953. 7 Jourard, S. M., and R. M. Remy. Perceived parental attitudes, the self, and security. Journal of Consulting Psychology 19:364-66, 1955. 8 Weinberg, J. R. A further investigation of body cathexis and the self. Journal of Consulting Psychology 24:277, 1960. 9 Tucker, L. A. Internal structure, factor satisfaction, and reliability of the body cathexis scale. Perceptual and Motor Skills 53:891-96, 1981. 10 Bloom, B. S., M. D. Engelhart, E. J. Furst, W. H. Hill, and D. R. Krathwohl. Taxonomy of educational objectives. Handbook I: Cognitive domain, New York: Longman, Inc., 1956,207 pp. 11 Gronlund, N. E. Measurement and evaluation in teaching, 4th ed., New York: Macmillan Publishing Co., Inc., 1981, pp. 99-101, 178-200, 258-60. 12 Grier, J. B. The number of alternatives for optimum test
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13 14
15 16
reliability. Journal of Educational Measurement 12:10913, 1975. Hollingshead, A. B., and M. M. Redlich. Social class and mental illness, New York: Wiley, 1958, 442 pp. National Center for Health Statistics. Height and weight of youths 12-17 years. United States 1966-1970, Vital and Health Statistics, Public Health Service Publication Series 11, No. 124, 1973, pp. 35,43,50-61. SAS Institute. SAS user's guide: Basics, 1982 ed., Cary, NC: SAS Institute, Inc., 1982, pp. 501, 513-26. SPSS, Inc. SPSSx user's guide, Chicago: McGraw Hill, 1983, p. 458.
17 Clifford, E. Body satisfaction in adolescence. Perceptual and Motor Skills 33:119-25, 1971. 18 Skinner, J. D., and M. J. Woodburn. Nutrition knowledge of teenagers. Journal of School Health 54:71-74, 1984. 19 Dwyer, J. T., J. J. Feldman, and J. Mayer. Nutritional literacy of high school students. Journal of Nutrition Education 2:59-65, 1970. 20 Mehrens, W. A., and I. J. Lehmann. Measurement and evaluation in education and psychology, 2d ed., New York: Holt, Reinehart, and Winston, 1978, p. 107.
TEENAGE MOTHERS AND BREASTFEEDING In the U.S., adolescent mothers account for 20% of the nation's live births. Given that teenage girls have notoriously poor diets, Lipsman, Dewey, and Lonnerdal (Journal of Pediatric Gastroenterology and Nutrition 4:426-34, 1985) sought to discover whether teenage mothers (80% of their sample was between ages 16-18) were capable of successfullactation. The study investigated maternal dietary intake, breast milk composition, and infant growth (as an indicator of the adequacy of breast milk volume). All 25 mothers in this study were involved in high school programs for pregnant teens and teen parents, and all of the programs included nutrition information. Although participants in this study were generally of low socioeconomic status, the average weight gain during pregnancy (38 lbs.) and mean birth weight (3,310 g) were well above those commonly reported for teenage mothers. Therefore, participants in this study probably began lactation with a greater reserve of body fat than do many other teens. During lactation, breast milk lactose concentrations were significantly lower than adult values. However, it is unlikely that the low lactose concentration adversely affected infant health to a great extent. Even though all dietary intake factors were favorable, the investigators found that levels of breast milk calcium among the teenage mothers in this study were lower than those reported among adult mothers. No single cause can be identified, but the authors suggest several possibilities: The mother's linear growth is usually completed by the age of 17, but skeletal growth, which requires calcium, may continue for a few more years; high levels of protein may stimulate calcium losses in the urine (calcium intake was 10% above the RDA while protein averaged 76% above the RDA); and a high dietary phosphorus-to-calcium ratio may alter calcium metabolism. Despite the low lactose concentration and the low calcium breast milk levels, infant growth was satisfactory for the 14 infants who were exclusively breastfed for 3 months or more. And although the other 11 infants were supplemented with formula before 3 months, poor growth was a reason for supplementation in only 3 cases. Thus, it appears that milk volume was adequate for 88% of the mothers. The two most common reasons given for breastfeeding were "infant health" and "convenience" followed by "prenatal and nutrition classes at school" and "cost." Twenty-one mothers breastfed for more than 3 months, and at least 9 continued beyond 6 months. This commitment was longer than expected. Besides teacher promotion of breastfeeding, peers within the programs provided encouragement to breastfeed. This support group helped the mothers resist pressure from family members or boyfriends to stop breastfeeding. Thus, with active counseling and support, teenage mothers in this study were capable of successful lactation. VOLUME 18 NUMBER 3
1986
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J.
AMOS2
IDepartment of Food and Nutrition and 2Department of Home Economics Education, College of Home Economics, Iowa State University, Ames, Iowa 50011 ABSTRACT This study examined the relationship between body-image satisfaction and knowledge of nutrition concepts related to weight control among 138 adolescent females. We administered a questionnaire to females aged 14 to 16, and obtained height and weight measurements. Sixty percent of the participants expressed more satisfaction than dissatisfaction with their bodies. Body aspects that these subjects were most frequently dissatisfied with were weight, hips, thighs, and bottom. Taller girls were more satisfied with their height than shorter girls, and lighter-weight girls were more satisfied with their weight than heavier girls. We used a multiple-choice test to assess nutrition knowledge concepts relevant to weight control. In general, the subjects seemed to know how to lose weight (using principles of energy intake and expenditure) but lacked knowledge of safe and reasonable dieting practices. The participants' nutrition knowledge test scores tended to increase with an increase in the mothers' education and socioeconomic levels. We did not find a significant correlation between body-image satisfaction and nutrition knowledge. (JNE 18:000-000, 1986)
During adolescence there is an increased awareness of self, with special focus on weight and appearance. Consequently, adolescents often compare their bodies with culturally defined ideal physiques. Unfortunately, Western cultures idealize thinness for women (1), and few adolescent females possess physiques that match these standards. Because adolescents are sensitive about weight and appearance, they are keenly aware of ways in which their developing bodies do not measure up to the cultural ideals. Thus, most adolescent females are dissatisfied with their body images. Numerous studies have investigated body-image dissatisfaction among both normal adolescents and adolescents with eating disorders (2). Adolescent females' body-image dissatisfaction often manifests itself in efforts to lose weight by dieting (3-5). Furthermore, Dwyer et al. (3) reported that 17to 18-year-old females who had dieted had a higher level of nutrition knowledge related to weight control than nondieters. Because dissatisfaction with body image seems to be a major stimulus for dieting among adolescent females, we hypothesized that knowledge of weight-control concepts would increase with a decrease in body-image satisfaction. The purpose of this VOLUME 18 NUMBER 3
1986
study was to examine the relationship between bodyimage satisfaction and knowledge of nutrition concepts related to weight control among adolescent females.
METHODS
Instrument development. We designed a questionnaire to gather data concerning adolescents' bodyimage satisfaction and their knowledge of nutrition concepts related to weight control, and demographic information such as their parents' socioeconomic levels and the adolescents' birth dates, weights, and heights. The body-image and nutrition knowledge components of the instrument are described below. Body image is difficult to measure adequately, and many instruments have been devised. Each instrument measures a slightly different aspect of body selfperception. Because low levels of body-image satisfaction are associated with adolescent dieting practices, we selected Secord and Jourard's Body Cathexis Scale (6), which assesses satisfaction with body-image. The Body Cathexis Scale lists a series of 20 body parts or aspects. Using a Likert-type scale from 1 (very dissatisfied) to 5 (very satisfied), participants circled how satisfied they felt with each body part or aspect listed. Several researchers (7-9) have found the reliability of the Body Cathexis Scale acceptable. To measure knowledge of nutrition concepts relevant to weight control, we constructed a test consisting of 24 multiple-choice items in the content areas of energy and energy balance. While constructing the test, we addressed content validity by following a table of specifications and by writing items to measure the behavioral objectives identified for each concept. We limited behavioral objectives to the lower two levels of the cognitive domain, knowledge and comprehension, as defined by Bloom et al. (10). Additionally, in writing the test items, we followed Gronlund's (11) guidelines for multiple-choice item construction, and we provided three alternative responses for each item (12). Four university nutrition faculty reviewed the test for content-related validity. JOURNAL OF NUTRITION EDUCATION
123
Using 14 adolescent females, ages 14 to 16, we pilottested the questionnaire to determine the clarity of directions and items. To refine the nutrition knowledge test, we analyzed the items (as described in the data analysis section of this article), and we revised three items based on analysis results.
schools were combined. Frequencies and percentages were calculated, and Spearman's rho correlation coefficients were computed between major variables. The level of significance selected for statistical analysis was .05.
Sample selection and data collection. We invited adolescent girls ages 14 to 16, in grades 8 through 11, from six junior and senior high schools to participate in the study (Note 1). All the schools were located in rural communities. Based on availability, we chose schools to obtain participants from the southern, central, and northern sections of the state. Students who were willing to participate and had written parental permission were included in the study. The major reasons for nonparticipation were that students reportedly forgot to have the parental permission form signed prior to data collection or they did not wish to have body weight taken. Demographic differences between participants and nonparticipants were not measured. We collected data from 142 students during class time (with the permission of the classroom teachers) or during study hall. After completing the questionnaire, each student was privately weighed and measured for height. For participating in the study, students were given their height and weight data.
RESULTS AND DISCUSSION
Data analysis. We excluded data from 4 of the 142 junior high and high school students who participated in our study. One subject was eliminated because of her age', another because of pregnancy, and 2 because of diseases that potentially influence body-image satisfaction. The university's test and evaluation service analyzed the nutrition knowledge test. Statistical analyses included a Kuder-Richardson-20 (KR-20) estimate of reliability, and a mean, standard deviation, and variance based on correct responses. Indices of difficulty and discrimination were calculated for test items (11). Next, by using each parent's occupation and level of educational attainment, socioeconomic level was determined according to the calculations described by Hollingshead (13). The total body-image satisfaction scores were calculated by adding the numerical responses for each body part or aspect and dividing by the total number of responses (6). Finally, based on percentile values from the National Center for Health Statistics (NCHS) (14), heights were assigned heightfor-age percentiles, and weights were assigned weight-for-height-and -age percentiles. Additional statistical procedures were carried out using packaged computer programs (15, 16). Since significant differences between schools were not found using the Scheffe procedure, the data from all 124
JOURNAL OF NUTRITION EDUCATION
Description of the sample. The participants' ages were well distributed, with slightly more 15-year-olds (39.8%) than 14- (31.9%) or 16- (28.3%) year-olds. Anthropometric measurements indicated that participants in our study were somewhat taller and heavier than the 14- to 16-year-old female sample from which the NCHS percentiles were derived, with approximately 40% of the participants in our study above the 75th height-for-age percentile, and 27% above the 75th weight-for-height-and-age percentile. The socioeconomic classifications of the participants' parents were divided into five levels, and tended to cluster in the middle three levels. However, compared to the fathers' socioeconomic classifications, the mothers' socioeconomic classifications were skewed toward the lower levels. This is possibly due to the relatively low wages associated with many of the jobs held by the mothers. Body-image satisfaction. We calculated response frequencies for each of the 20 body aspects included in the body-image satisfaction scale. Body aspects that the participants were most frequently "very dissatisfied" with were weight, hips, thighs, and bottom, respectively. Body aspects that most frequently received "very satisfied" ratings were height, leg-length, hands, width of shoulders, and calves, respectively. Overall, the body aspects related to skeletal size were more satisfying than those related to body fat. No respondent's total body-image satisfaction score was below 1.50 or above 4.51, indicating lack of any total body-image scores at either the "very dissatisfied" or "very satisfied" end of the scale, respectively. Sixty percent of the respondents had scores above 3.00, indicating an overall degree of satisfaction. The mean total body-image satisfaction score for the girls in this study was 3.16. Similar mean scores have been reported for college women (6) and 11- to 19-year-old females (17). Nutrition knowledge. Table 1 lists the average percentage of correct responses to items measuring each objective evaluated by the nutrition knowledge test. Because the independence of each item on the test was not ascertained, the data in Table 1 represent a relative ranking of the participants' knowledge regarding each objective. The nutrition knowledge test contained 9 VOLUME 18
NUMBER 3
1986
Average percent of correct responses to itemsa measuring each objective evaluated by the nutrition knowledge test
Table 1.
Objectiveb,c
Mean Percent of Correct Responses for Items Measuring Objective
2.7
Recognize that excess energy is stored as body fat Recognize the source of kilocalories 1.2 1.4 Identify the nutrients that supply kilocalories 2.10 Recognize relative differences in energy expenditure required for various activities 2.11 Recognize how specific foods, based on their caloric content, can affect energy balance 2.6 Recognize that weight gain is a normal part of growth and development 1.5 Distinguish between high and low kilocalorie foods 1.1 Select the correct definition of a calorie 2.4 Recognize a reasonable number of kilocalories a teenage girl should consume on a weight-loss diet 2.9 Recognize the relationships among food intake, activity, and body weight 1.6 Identify foods that contain fat, carbohydrate, and protein 2.5 Identify a reasonable rate of weight loss Recognize that fat is more calorically 1.3 dense than carbohydrate and protein 2.3 Identify the range of kilocalories needed per 24 hours by the average teenage girl 2.8 Recognize that body fat is essential for health 2.1 Recognize the calorie deficit that produces a one-pound loss of body fat 2.2 Recognize that the resting body uses energy
83% 75 69 68 68 67 63 57 57 56 50 45 43 34 27 22 19
aSome objectives include the results (% of correct responses) from more than 1 item. bObjectives 1.1-1.9 measure an energy concept. CObjectives 2.1-2.9 measure an energy balance concept.
items that measured 6 objectives related to the concept of energy. With one exception, the average percentage of correct responses was 50% or greater for items measuring these objectives. Incorrect responses to the items measuring the objective of "recognizing that fat is more calorically dense than carbohydrate and protein" reflect the common misconception that carbohydrates are fattening, and the limited recognition that fat is calorically dense. VOLUME 18 NUMBER 3
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Fifteen items on the nutrition knowledge test measured objectives related to the concept of energy balance. The percentage of correct responses was low for items that measured knowledge of relatively technical aspects of energy balance, such as knowing the size of the calorie deficit that produces a one-pound loss of body fat, and knowing that the resting body uses energy. Knowledge of these kinds of facts may not be essential for successful dieting. However, fewer than half of the participants correctly answered items for 3 objectives that are more essential for safe weight loss. These objectives dealt with knowing how many kilocalories an average teenage girl requires per day, identifying a reasonable rate of weight loss, and recognizing that some body fat is essential for health. Because knowledge level of certain energy and energy balance topics appeared high, while knowledge level of others ofthese topics was quite low, future studies should attempt to find out where teens receive information about these topics. Whether the lack of correct information is a result of misinformation or lack of information is not known. Other researchers who have administered nutrition knowledge tests to groups of adolescents have measured selected aspects of energy and energy balance. Skinner and Woodburn (18), using a multiple-choice test format, studied the nutrition knowledge of 1,193 male and female teens. They reported that 45% of their sample incorrectly defined calories as "the amount of fat in foods." In our study, 40% of the sample defined calories as the fat content of food. But Skinner and Woodburn also report that only 15% of their sample knew the relative calorie content of selected foods. In contrast, 63% of the sample tested in our study correctly answered questions regarding the relative calorie content of foods, a percentage similar to that found by Dwyer et al. (19). They reported that 58% of the 722 ninth- to twelfth-grade girls in their study correctly responded to multiple-choice questions on the caloric value of foods. The mean score for the nutrition knowledge test used in this study was 13.24 of a possible 24, with a standard deviation of 3.07 and a range of 7 to 22. The standard error of measurement was 2.21 in raw scores. The criteria for evaluating the effectiveness of each test item were a difficulty index ranging from 30 to 70; a discrimination index >0.20 or, if > 0.40, with a standard deviation> 0.20; and distracters chosen by three or more respondents (11). Of the 24 items, 14 met all three criteria, and 10 met two. The KR-20 formula for calculating an estimate of the internal consistency of the test revealed a coefficient of 0.48. This value is relatively low according to Mehrens and Lehmann (20), who recommend a coefficient ~ 0.65 for tests involving groups of people. The most probable explanation for the relatively low interJOURNAL OF NUTRITION EDUCATION
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nal consistency lies in the length of the test. Had the test been longer than 24 items, we could have obtained a more reliable sampling of the content areas. In addition, the mean score of 13.24 out of 24 indicates that the participants found this test difficult. As a result, scores tended to cluster.
adolescent girls. However, we also found that teenage girls lacked knowledge about certain basic weight control principles. 0
Statistical correlations. Spearman's rho correlation coefficients were computed between body-image satisfaction scores, nutrition knowledge test scores, and descriptive variables. We had hypothesized that a significant, negative correlation would exist between body-image satisfaction scores and nutrition knowledge test scores, but we did not find a significant correlation. Thus, girls in this sample who had relatively low levels of body-image satisfaction did not have a better knowledge of nutrition concepts related to weight control than did their more satisfied counterparts. However, we did find significant correlations between other variables. The participants' nutrition knowledge test scores tended to increase with an increase in the mothers' educational levels (r = 0.18, P :5 .05) and the mothers' socioeconomic levels (r = 0.26, P :5 .01). Numerous studies with adults have reported that nutrition knowledge is positively correlated with education and income. The participants' body-image satisfaction scores were negatively correlated with their weight-forheight-and-age percentiles (r = -0.34, P :5 .01). These results indicate that, at a given height and age, lighter-weight girls tended to be more satisfied with their body image than were heavier girls. In addition, satisfaction with weight was negatively correlated with weight-for-height-and-age percentile (r = -0.51, P :5 .001), whereas satisfaction with height was positively correlated with height-for-age percentile (r = 0.50, P :5 .001). In this study, we did not find a statistically significant relationship between nutrition knowledge and weight-for-height-and-age. However, Dwyer et a1. (3) found that the heavier female adolescents were more dissatisfied with body image yet tended to know more about nutrition than their lighter-weight counterparts. This difference between the studies may be the result of using different nutrition knowledge tests, or it may be because our study used a smaller sample of adolescents than Dwyer et a1. (3). In our sample, 36 girls were above the 75th weight-for-height-and-age percentile, and only 15 were above the 90th percentile. Thus, the subsample of potentially obese girls was relatively small. Many variables likely have a bearing on the level of body-image satisfaction and nutrition knowledge of female adolescents. Dissatisfaction with their body image seems to be a primary reason for dieting among
Journal paper no. J-11969 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project no. 2663, a contributing project to North Central Regional Research project No. 173, and journal paper no. 357 of the Home Economics Research Institute, College of Home Economics, Iowa State University, Ames, Iowa. Based on a thesis submitted by Robin H. Searles in partial fulfillment of the requirements for the degree of Master of Science. The authors gratefully acknowledge the cooperation of school systems in Iowa that participated in this project.
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ACKNOWLEDGMENT
NOTE The Iowa State University Committee on the Use of Human Subjects in Research approved the instrument and research procedures.
LITERATURE CITED 1 Garner, D. M., P. E. Garfinkel, D. Schwartz, and M. Thompson. Cultural expectations of thinness in women. Psychological Reports 47:483-91, 1980. 2 Garner, D. M., and P. E. Garfinkel, eds. Handbook of psychotherapy for anorexia nervosa and bulimia, New York: Guilford Press, 1985, 592 pp. 3 Dwyer, J. T., J. J. Feldman, and J. Mayer. Adolescent dieters: Who are they? American Journal of Clinical Nutrition 20:1045-56, 1967. 4 Dwyer, J. T., J. J. Feldman, C. C. Seltzer, and J. Mayer. Adolescent attitudes toward weight and appearance. Journal of Nutrition Education 1:14-19, 1969. 5 Kaufmann, N. A., R. Poznanski, and K. Guggenheim. Teenagers dieting for weight control. Nutrition and Metabolism 16:30-37,1974. 6 Secord, P. F., and S. M. Jourard. The appraisal of body cathexis and the self. Journal of Consulting Psychology 17:343-47,1953. 7 Jourard, S. M., and R. M. Remy. Perceived parental attitudes, the self, and security. Journal of Consulting Psychology 19:364-66, 1955. 8 Weinberg, J. R. A further investigation of body cathexis and the self. Journal of Consulting Psychology 24:277, 1960. 9 Tucker, L. A. Internal structure, factor satisfaction, and reliability of the body cathexis scale. Perceptual and Motor Skills 53:891-96, 1981. 10 Bloom, B. S., M. D. Engelhart, E. J. Furst, W. H. Hill, and D. R. Krathwohl. Taxonomy of educational objectives. Handbook I: Cognitive domain, New York: Longman, Inc., 1956,207 pp. 11 Gronlund, N. E. Measurement and evaluation in teaching, 4th ed., New York: Macmillan Publishing Co., Inc., 1981, pp. 99-101, 178-200, 258-60. 12 Grier, J. B. The number of alternatives for optimum test
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reliability. Journal of Educational Measurement 12:10913, 1975. Hollingshead, A. B., and M. M. Redlich. Social class and mental illness, New York: Wiley, 1958, 442 pp. National Center for Health Statistics. Height and weight of youths 12-17 years. United States 1966-1970, Vital and Health Statistics, Public Health Service Publication Series 11, No. 124, 1973, pp. 35,43,50-61. SAS Institute. SAS user's guide: Basics, 1982 ed., Cary, NC: SAS Institute, Inc., 1982, pp. 501, 513-26. SPSS, Inc. SPSSx user's guide, Chicago: McGraw Hill, 1983, p. 458.
17 Clifford, E. Body satisfaction in adolescence. Perceptual and Motor Skills 33:119-25, 1971. 18 Skinner, J. D., and M. J. Woodburn. Nutrition knowledge of teenagers. Journal of School Health 54:71-74, 1984. 19 Dwyer, J. T., J. J. Feldman, and J. Mayer. Nutritional literacy of high school students. Journal of Nutrition Education 2:59-65, 1970. 20 Mehrens, W. A., and I. J. Lehmann. Measurement and evaluation in education and psychology, 2d ed., New York: Holt, Reinehart, and Winston, 1978, p. 107.
TEENAGE MOTHERS AND BREASTFEEDING In the U.S., adolescent mothers account for 20% of the nation's live births. Given that teenage girls have notoriously poor diets, Lipsman, Dewey, and Lonnerdal (Journal of Pediatric Gastroenterology and Nutrition 4:426-34, 1985) sought to discover whether teenage mothers (80% of their sample was between ages 16-18) were capable of successfullactation. The study investigated maternal dietary intake, breast milk composition, and infant growth (as an indicator of the adequacy of breast milk volume). All 25 mothers in this study were involved in high school programs for pregnant teens and teen parents, and all of the programs included nutrition information. Although participants in this study were generally of low socioeconomic status, the average weight gain during pregnancy (38 lbs.) and mean birth weight (3,310 g) were well above those commonly reported for teenage mothers. Therefore, participants in this study probably began lactation with a greater reserve of body fat than do many other teens. During lactation, breast milk lactose concentrations were significantly lower than adult values. However, it is unlikely that the low lactose concentration adversely affected infant health to a great extent. Even though all dietary intake factors were favorable, the investigators found that levels of breast milk calcium among the teenage mothers in this study were lower than those reported among adult mothers. No single cause can be identified, but the authors suggest several possibilities: The mother's linear growth is usually completed by the age of 17, but skeletal growth, which requires calcium, may continue for a few more years; high levels of protein may stimulate calcium losses in the urine (calcium intake was 10% above the RDA while protein averaged 76% above the RDA); and a high dietary phosphorus-to-calcium ratio may alter calcium metabolism. Despite the low lactose concentration and the low calcium breast milk levels, infant growth was satisfactory for the 14 infants who were exclusively breastfed for 3 months or more. And although the other 11 infants were supplemented with formula before 3 months, poor growth was a reason for supplementation in only 3 cases. Thus, it appears that milk volume was adequate for 88% of the mothers. The two most common reasons given for breastfeeding were "infant health" and "convenience" followed by "prenatal and nutrition classes at school" and "cost." Twenty-one mothers breastfed for more than 3 months, and at least 9 continued beyond 6 months. This commitment was longer than expected. Besides teacher promotion of breastfeeding, peers within the programs provided encouragement to breastfeed. This support group helped the mothers resist pressure from family members or boyfriends to stop breastfeeding. Thus, with active counseling and support, teenage mothers in this study were capable of successful lactation. VOLUME 18 NUMBER 3
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