Addictive Behaviors, Vol. 15, pp. 147-152, Primed in the USA. All rights reserved.
1990 Copyright
0306-4603/90 $3.00 + .OO e 1990 Pergamon Press plc
A PSYCHOMETRIC
STUDY OF RESTRAINT: THE IMPACT OF RACE, GENDER, WEIGHT AND MARITAL STATUS
MARY L. KLEM, ROBERT C. KLESGES, CHERYL R. BENE, and MICHAEL W. MELLON Memphis State University Abstract - This investigation examined the psychometric characteristics of the Revised Restraint Scale and its two subscales (Weight Fluctuation, Concern for Dieting) in a university with a diverse student population. Subjects were 497 individuals (15 1 men, 346 women) ranging in age from 17 to 57 years (mean age = 21 years). Of the total sample, 70% were White (n = 348) and 22% were Black (n = 109). Results indicated significant between-groups differences on the total Restraint scores, with Whites scoring higher than Blacks, females scoring higher than males, and overweight individuals scoring higher than normal weight individuals. Similar results were found with both of the subscales. Despite the large number of between-groups differences observed, internal reliabilities of the total scale and the two subscales were similar and generally high within each of the categories surveyed. In general, however, lower reliabilities were observed for overweight subjects compared to normal weight subjects. The results of this study suggest that restraint status may vary as a function of individuals’ demographic characteristics.
A number of studies have examined the relationship between eating behavior, obesity and the construct of dietary restraint (Ruderman, 1986). Originally developed as an alternative to Schacter’s (1968) internality-externality hypothesis of obesity, restraint theory hypothesizes that eating patterns are influenced by both physiological cues that prompt a desire to eat and cognitively mediated processes that inhibit the desire to eat. While a large number of studies have utilized the restraint scale in both laboratory and field research (see Ruderman, 1986, for a review), there have been a limited number of studies that have examined the psychometric properties of the restraint scale in both normal weight and overweight populations. Studies examining the internal consistency of the restraint scale have found the scale’s reliability to vary as a function of the proportion of obese individuals in the utilized sample. When used with normal weight groups, the alpha reliability coefficients of the scale have been found to range from .79 (Johnson, Lake, & Mahan, 1984) to .86 (Ruderman & Christensen, 1983). When administered to obese individuals, however, the alpha reliability coefficients have typically been in the .50 range (Johnson et al., 1984; Ruderman & Christensen, 1983). Thus, it appears that the internal reliability of the total scale is adequate when used with normal weight samples, but decreases when an obese sample is used. Although it has been strongly recommended that studies of restraint “consider the two factors of restraint separately, as well as the scale as a whole” (Ruderman, 1986; p. 259), the reliabilities of the subscales of restraint (i.e., Concern for Dieting and Weight Fluctuation) in normal weight and obese populations have not yet been evaluated. To our knowledge, no studies have sought to determine if any variables other than weight status have an impact on total restraint scores and subscale scores. It is reasonable to assume that demographic variables such as age, gender, marital status and race may affect scores on a measure of chronic dieting. For example, Klesges and Klesges (1988) found that older This study was supported by two grants awarded to the second author by the National Heart, Lung, and Blood Institute (HL36553; HL37339) and a Centers of Excellence grant awarded to the Department of Psychology, Memphis State University, by tbe state of Tennessee. Requests for reprints should be sent to Mary L. Klem, M.S., Center for Applied Psychological Research, Department of Psychology, Memphis State University, Memphis, TN 38152. 147
148
MARY
L. KLEM et al.
females are less likely than younger females to use the dieting strategy of smoking, suggesting that older women may be less concerned with dieting in general. It has also been established that rates of obesity are higher in both minority populations and older age groups (Department of Health, Education, and Welfare, 1985); again, this suggests that concern with dieting and other weight issues may be less, or at least at different levels, in these populations than in others. Although, to our knowledge, dieting strategies have not been systematically investigated as a function of marital status, it seems reasonable to hypothesize that chronic dietary patterns may perhaps fluctuate as a function of this demographic variable. Finally, virtually all of the research conducted on the psychometric properties of the restraint scale have typically utilized Caucasian, college-age females, and no study has yet looked at the collective impact of basic demographic variables on levels of restraint. Thus, the purpose of this investigation was to investigate the relationship between basic demographic variables (gender, age, race, marital status) and dietary restraint scores, as well as to assess internal consistency of the restraint scale as a function of these potential moderator variables. METHOD
Subjects
Subjects were 497 individuals (151 men, 346 women) recruited from introductory psychology classes. Subjects were told they were participating in a study on holiday eating habits, and received extra credit for their participation. Of the total sample, 70% (348) of the subjects were White and 22% (109) were Black (the remaining 8% were members of various other ethnic groups and were excluded from data analysis). Self-reported weights indicated that subjects weighed, on the average, 140 pounds (SD = 28.84). Of the total sample, 13% (65) of the subjects had relative weights at or above the 75th percentile, and 87% had relative weights below the 75th percentile. The mean age was 21 years (SD = 6.25), with 78% (390) of the subjects being at or below 21 years of age, and 22% (109) of the sample being above 21 years of age. Ages ranged from 17 to 57 years. Procedure
As a part of their participation in a larger study of holiday eating patterns (Klesges, Klem, & Bene, in press), subjects completed the Herman & Polivy (1980) Revised Restraint Scale. To prevent subjects from becoming aware of the purpose of the study, items from the scale were interspersed with general questions on food preferences and family eating habits. Each subject was also asked to report his/her height, weight, age, race, gender and marital status. Based on their self-reported height and weight, relative weights of the subjects were calculated (gender, age, and height adjusted) using the latest Department of Health, Education and Welfare norms (1979). Subjects were classified as overweight if they met or exceeded the 75th percentile of weight, adjusted for height, gender and age. Subjects at or below 21 years of age were classified as students in an age range typical for an undergraduate institution. Subjects above 21 years of age were classified as “older than average” students who might differ from the younger students on the variables of interest. Subject scores on the restraint scale were then compared as a function of their relative weight, gender, race, age and marital status. RESULTS
Between-groups analyses Total restraint score. The average overall score on the total restraint
scale was 12.56 (SD = 5.88), and scores ranged from 1 to 28. An analysis of variance (ANOVA) performed on
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MARY L. KLEM et al.
150
Table 2. Cronbach’s
Alpha for Total Score and Subscales Total score
CD
WF
Total sample
.78
.74
.66
Gender Males Females
.77 .78
.74 .72
.67 .68
Race White Black
.77 .76
.76 .70
.64 .64
Age 21 and under Over 21
.75 .81
.73 .75
.@I .78
Marital status Smgle Married
.77 .79
.74 .72
.63 .77
Weight Normal weight Overweight
.78 .68
.75 .65
.65 .54
n = 497
significantly higher on the WF subscale than did Blacks, F( 1,487) = 56.75, p < .OOO1, and overweight subjects scored consistently higher than did normal weight subjects, F( 1, 487) = 91.73, p < .OOOl . Married subjects reported scores significantly greater than those reported by unmarried subjects, F(1, 487) = 7.50, p < .Ol (see Table 1). Similar to the findings in the analyses of the total score, an ANOVA also revealed an age by gender interaction, F( 1, 487) = 4.06, p < .05. Post hoc analyses of Tukey’s Least Significant Differences indicated that subjects of both sexes (n of females = 80; n of males = 35) who were above the age of 21 scored higher on the WF subscale than did subjects (n of females = 273; n of males = 125) under 21 years of age. In addition, the increase in scores seen as a function of age was larger for females than for males. Reliability (internal consistency). The reliability of the total scale, as well as the CD and WF subscales, was assessed for the total sample and by demographic variables, using Cronbach’s alpha. The results are presented in Table 2. Despite the large number of between-groups observed above, alphas for the total sample and for groups within each of the demographic categories were similar and were generally high (see Table 2). The exception to this involved the alphas for the normal weight and overweight subjects. As can be seen from Table 2, alpha coefficients for all three scores were consistently lower for overweight individuals. However, when these alphas were assessed using a procedure for the comparison of correlations, the differences between alphas were not significant (ps = 11 to .18). DISCUSSION
The results of this study indicate that various demographic groups have different patterns of responses on the Restraint Scale and its two subscales. White subjects scored significantly higher on the total scale than did Blacks, while females scored significantly higher than did males. In addition, overweight subjects had total restraint scores significantly higher than those observed among normal weight individuals. Analyses of scores on the CD and WF subscales also revealed numerous between-groups differences on these demographic comparisons. On both subscales, scores of White individuals were significantly higher than those
Psychometric study of restraint
151
of Blacks, and overweight subjects scores were higher than normal weight subjects scores. In addition, CD scores for females were significantly higher than CD scores for males, and married subjects received CD scores significantly greater than those received by unmarried subjects. Despite the consistent pattern of between-groups differences on restraint scores, reliabilities for the total score and the two subscales were similar and generally high within each of the demographic categories. Overweight individuals had consistently lower reliabilities than normal weight individuals, although these differences were not significant. The presence of numerous between-groups differences on scale scores indicates that it is inappropriate to assume that level of restraint is unaffected by a subject’s background characteristics. That is, the level of restraint reported by an individual may vary as a function of the individual’s age, gender, race or marital status. Recent studies, possibly seeking to eliminate problems associated with defining restraint on the basis of a median split of the sample, have recommended that a total score of 15 or more should differentiate between dieters and non-dieters (e.g., Herman, Polivy, Lank, & Heatherton, 1987). While a universal cutoff point is clearly preferable to a simple median split, it is clear that further normative data on the Restraint Scale is required before any such guideline may be issued. It is not clear why the demographic groups respond differentially on the scale. As noted earlier, rates of obesity are higher in various populations (DHEW, 1985); it may be that this greater prevalence makes obesity more “acceptable’ ’ to population members. The members may, in turn, feel less pressure to lose weight and be generally unconcerned with dieting. Of particular interest is the interaction between age and gender: while young females appear more restrained than young males, this difference disappears in males and females over the age of 21. Perhaps females over 21 years of age are subject to less societal or peer pressure to focus on weight issues, or perhaps they simply tire of constant dieting and the fluctuations in weight it may bring about. Future research in this area should involve measurement of actual dieting behaviors and investigate in a prospective manner the changes, if any, in these behaviors over time. Further research is also needed to explore the issue of reliability and validity of the Restraint Scale in different populations. The exact meaning of the mean differences observed in the current study is unclear. Until the restraint scores are validated against an external criterion, differences in restraint scores may or may not reflect true differences in levels of restraint between demographic groups. Thus, future studies of restraint should explore the relationship between actual food consumption and levels of restraint within various demographic populations. Such studies will help to determine the prevalence of restraint and its relationship to eating behaviors in diverse populations. Despite the between-groups differences observed, internal reliabilities for total scores and subscale scores were generally high, suggesting that restraint is a construct with high internal consistency across a number of demographic variables. Our results also indicate, consistent with other findings (e.g., Johnson et al., 1984; Ruderman, 1983) that internal consistency of the scale is lower when the scale is administered to obese samples. The magnitude of this difference, however, was not significant. Nonetheless, future studies should focus on exploring more closely the factors assumed to produce obese-normal weight differences in restraint scores. In summary, the results of this study support the hypothesis that restraint scores vary as a function of several subject characteristics. It is also clear that restraint scores are less reliable and generally higher in obese samples. If the construct of restraint is to be a useful tool in understanding eating patterns, future research must continue to focus on variables which affect restraint scores and must also look beyond the laboratory setting to the impact of restraint scores on actual eating behaviors.
152
MARY L. KLEM et al
REFERENCES Department of Health, Education and Welfare. (1979). Weight by height and age for adults 18-74 years: U.S. 1971-1974 (Series 11: data from NCHS, No. 208; DHEW Publication No. 79-1656). Rockville, MD: DHEW. Department of Health, Education and Welfare. (1985). Report of the Secretary’s Task Force on Black and Minori Health: Executive summary (Task Force on Black and Minority Health). Washington, DC: U.S. Government Printing Office. Herman, C.P., & Polivy, J. (1980). Restrained eating. In A.J. Stunkard (Ed.), Obesity (pp. 208-225). Philadelphia: W.B. Saunders. Herman, C.P., Polivy, J., Lank, C.N., & Heatherton, T.F. (1987). Anxiety, hunger, and eating behavior. Journal of Abnormal Behavior, 96, 26&269. Johnson, W.G., Lake, L., & Mahan, M. (1984). Restrained eating: Measuring an elusive construct. Addictive Behaviors, 8, 413-418. Klesges, R.C., Klem, M.L., & Bene, C.R. (in press). The effects of dietary restraint, obesity and gender on holiday eating behavior and weight gain. Journal of Abnormal Psychology. Klesges, R.C., & Klesges, L.M. (1988). Cigarette smoking as a dieting strategy in a university population. International Journal of Eating Disorders, 7, 413419. Ruderman, A.J. (1986). Dietary restraint: A theoretical and empirical review. Psychological Bulletin, 99, 247-262. Ruderman, A.J., &Christensen, H. (1983). Restraint theory and its applicability to overweight individuals. Journal of Abnormal Psychology, 92, 210-215. Schacter, S. (1968). Obesity and eating. Science, 161, 751-756.
1990 Copyright
0306-4603/90 $3.00 + .OO e 1990 Pergamon Press plc
A PSYCHOMETRIC
STUDY OF RESTRAINT: THE IMPACT OF RACE, GENDER, WEIGHT AND MARITAL STATUS
MARY L. KLEM, ROBERT C. KLESGES, CHERYL R. BENE, and MICHAEL W. MELLON Memphis State University Abstract - This investigation examined the psychometric characteristics of the Revised Restraint Scale and its two subscales (Weight Fluctuation, Concern for Dieting) in a university with a diverse student population. Subjects were 497 individuals (15 1 men, 346 women) ranging in age from 17 to 57 years (mean age = 21 years). Of the total sample, 70% were White (n = 348) and 22% were Black (n = 109). Results indicated significant between-groups differences on the total Restraint scores, with Whites scoring higher than Blacks, females scoring higher than males, and overweight individuals scoring higher than normal weight individuals. Similar results were found with both of the subscales. Despite the large number of between-groups differences observed, internal reliabilities of the total scale and the two subscales were similar and generally high within each of the categories surveyed. In general, however, lower reliabilities were observed for overweight subjects compared to normal weight subjects. The results of this study suggest that restraint status may vary as a function of individuals’ demographic characteristics.
A number of studies have examined the relationship between eating behavior, obesity and the construct of dietary restraint (Ruderman, 1986). Originally developed as an alternative to Schacter’s (1968) internality-externality hypothesis of obesity, restraint theory hypothesizes that eating patterns are influenced by both physiological cues that prompt a desire to eat and cognitively mediated processes that inhibit the desire to eat. While a large number of studies have utilized the restraint scale in both laboratory and field research (see Ruderman, 1986, for a review), there have been a limited number of studies that have examined the psychometric properties of the restraint scale in both normal weight and overweight populations. Studies examining the internal consistency of the restraint scale have found the scale’s reliability to vary as a function of the proportion of obese individuals in the utilized sample. When used with normal weight groups, the alpha reliability coefficients of the scale have been found to range from .79 (Johnson, Lake, & Mahan, 1984) to .86 (Ruderman & Christensen, 1983). When administered to obese individuals, however, the alpha reliability coefficients have typically been in the .50 range (Johnson et al., 1984; Ruderman & Christensen, 1983). Thus, it appears that the internal reliability of the total scale is adequate when used with normal weight samples, but decreases when an obese sample is used. Although it has been strongly recommended that studies of restraint “consider the two factors of restraint separately, as well as the scale as a whole” (Ruderman, 1986; p. 259), the reliabilities of the subscales of restraint (i.e., Concern for Dieting and Weight Fluctuation) in normal weight and obese populations have not yet been evaluated. To our knowledge, no studies have sought to determine if any variables other than weight status have an impact on total restraint scores and subscale scores. It is reasonable to assume that demographic variables such as age, gender, marital status and race may affect scores on a measure of chronic dieting. For example, Klesges and Klesges (1988) found that older This study was supported by two grants awarded to the second author by the National Heart, Lung, and Blood Institute (HL36553; HL37339) and a Centers of Excellence grant awarded to the Department of Psychology, Memphis State University, by tbe state of Tennessee. Requests for reprints should be sent to Mary L. Klem, M.S., Center for Applied Psychological Research, Department of Psychology, Memphis State University, Memphis, TN 38152. 147
148
MARY
L. KLEM et al.
females are less likely than younger females to use the dieting strategy of smoking, suggesting that older women may be less concerned with dieting in general. It has also been established that rates of obesity are higher in both minority populations and older age groups (Department of Health, Education, and Welfare, 1985); again, this suggests that concern with dieting and other weight issues may be less, or at least at different levels, in these populations than in others. Although, to our knowledge, dieting strategies have not been systematically investigated as a function of marital status, it seems reasonable to hypothesize that chronic dietary patterns may perhaps fluctuate as a function of this demographic variable. Finally, virtually all of the research conducted on the psychometric properties of the restraint scale have typically utilized Caucasian, college-age females, and no study has yet looked at the collective impact of basic demographic variables on levels of restraint. Thus, the purpose of this investigation was to investigate the relationship between basic demographic variables (gender, age, race, marital status) and dietary restraint scores, as well as to assess internal consistency of the restraint scale as a function of these potential moderator variables. METHOD
Subjects
Subjects were 497 individuals (151 men, 346 women) recruited from introductory psychology classes. Subjects were told they were participating in a study on holiday eating habits, and received extra credit for their participation. Of the total sample, 70% (348) of the subjects were White and 22% (109) were Black (the remaining 8% were members of various other ethnic groups and were excluded from data analysis). Self-reported weights indicated that subjects weighed, on the average, 140 pounds (SD = 28.84). Of the total sample, 13% (65) of the subjects had relative weights at or above the 75th percentile, and 87% had relative weights below the 75th percentile. The mean age was 21 years (SD = 6.25), with 78% (390) of the subjects being at or below 21 years of age, and 22% (109) of the sample being above 21 years of age. Ages ranged from 17 to 57 years. Procedure
As a part of their participation in a larger study of holiday eating patterns (Klesges, Klem, & Bene, in press), subjects completed the Herman & Polivy (1980) Revised Restraint Scale. To prevent subjects from becoming aware of the purpose of the study, items from the scale were interspersed with general questions on food preferences and family eating habits. Each subject was also asked to report his/her height, weight, age, race, gender and marital status. Based on their self-reported height and weight, relative weights of the subjects were calculated (gender, age, and height adjusted) using the latest Department of Health, Education and Welfare norms (1979). Subjects were classified as overweight if they met or exceeded the 75th percentile of weight, adjusted for height, gender and age. Subjects at or below 21 years of age were classified as students in an age range typical for an undergraduate institution. Subjects above 21 years of age were classified as “older than average” students who might differ from the younger students on the variables of interest. Subject scores on the restraint scale were then compared as a function of their relative weight, gender, race, age and marital status. RESULTS
Between-groups analyses Total restraint score. The average overall score on the total restraint
scale was 12.56 (SD = 5.88), and scores ranged from 1 to 28. An analysis of variance (ANOVA) performed on
par03
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Table 2. Cronbach’s
Alpha for Total Score and Subscales Total score
CD
WF
Total sample
.78
.74
.66
Gender Males Females
.77 .78
.74 .72
.67 .68
Race White Black
.77 .76
.76 .70
.64 .64
Age 21 and under Over 21
.75 .81
.73 .75
.@I .78
Marital status Smgle Married
.77 .79
.74 .72
.63 .77
Weight Normal weight Overweight
.78 .68
.75 .65
.65 .54
n = 497
significantly higher on the WF subscale than did Blacks, F( 1,487) = 56.75, p < .OOO1, and overweight subjects scored consistently higher than did normal weight subjects, F( 1, 487) = 91.73, p < .OOOl . Married subjects reported scores significantly greater than those reported by unmarried subjects, F(1, 487) = 7.50, p < .Ol (see Table 1). Similar to the findings in the analyses of the total score, an ANOVA also revealed an age by gender interaction, F( 1, 487) = 4.06, p < .05. Post hoc analyses of Tukey’s Least Significant Differences indicated that subjects of both sexes (n of females = 80; n of males = 35) who were above the age of 21 scored higher on the WF subscale than did subjects (n of females = 273; n of males = 125) under 21 years of age. In addition, the increase in scores seen as a function of age was larger for females than for males. Reliability (internal consistency). The reliability of the total scale, as well as the CD and WF subscales, was assessed for the total sample and by demographic variables, using Cronbach’s alpha. The results are presented in Table 2. Despite the large number of between-groups observed above, alphas for the total sample and for groups within each of the demographic categories were similar and were generally high (see Table 2). The exception to this involved the alphas for the normal weight and overweight subjects. As can be seen from Table 2, alpha coefficients for all three scores were consistently lower for overweight individuals. However, when these alphas were assessed using a procedure for the comparison of correlations, the differences between alphas were not significant (ps = 11 to .18). DISCUSSION
The results of this study indicate that various demographic groups have different patterns of responses on the Restraint Scale and its two subscales. White subjects scored significantly higher on the total scale than did Blacks, while females scored significantly higher than did males. In addition, overweight subjects had total restraint scores significantly higher than those observed among normal weight individuals. Analyses of scores on the CD and WF subscales also revealed numerous between-groups differences on these demographic comparisons. On both subscales, scores of White individuals were significantly higher than those
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151
of Blacks, and overweight subjects scores were higher than normal weight subjects scores. In addition, CD scores for females were significantly higher than CD scores for males, and married subjects received CD scores significantly greater than those received by unmarried subjects. Despite the consistent pattern of between-groups differences on restraint scores, reliabilities for the total score and the two subscales were similar and generally high within each of the demographic categories. Overweight individuals had consistently lower reliabilities than normal weight individuals, although these differences were not significant. The presence of numerous between-groups differences on scale scores indicates that it is inappropriate to assume that level of restraint is unaffected by a subject’s background characteristics. That is, the level of restraint reported by an individual may vary as a function of the individual’s age, gender, race or marital status. Recent studies, possibly seeking to eliminate problems associated with defining restraint on the basis of a median split of the sample, have recommended that a total score of 15 or more should differentiate between dieters and non-dieters (e.g., Herman, Polivy, Lank, & Heatherton, 1987). While a universal cutoff point is clearly preferable to a simple median split, it is clear that further normative data on the Restraint Scale is required before any such guideline may be issued. It is not clear why the demographic groups respond differentially on the scale. As noted earlier, rates of obesity are higher in various populations (DHEW, 1985); it may be that this greater prevalence makes obesity more “acceptable’ ’ to population members. The members may, in turn, feel less pressure to lose weight and be generally unconcerned with dieting. Of particular interest is the interaction between age and gender: while young females appear more restrained than young males, this difference disappears in males and females over the age of 21. Perhaps females over 21 years of age are subject to less societal or peer pressure to focus on weight issues, or perhaps they simply tire of constant dieting and the fluctuations in weight it may bring about. Future research in this area should involve measurement of actual dieting behaviors and investigate in a prospective manner the changes, if any, in these behaviors over time. Further research is also needed to explore the issue of reliability and validity of the Restraint Scale in different populations. The exact meaning of the mean differences observed in the current study is unclear. Until the restraint scores are validated against an external criterion, differences in restraint scores may or may not reflect true differences in levels of restraint between demographic groups. Thus, future studies of restraint should explore the relationship between actual food consumption and levels of restraint within various demographic populations. Such studies will help to determine the prevalence of restraint and its relationship to eating behaviors in diverse populations. Despite the between-groups differences observed, internal reliabilities for total scores and subscale scores were generally high, suggesting that restraint is a construct with high internal consistency across a number of demographic variables. Our results also indicate, consistent with other findings (e.g., Johnson et al., 1984; Ruderman, 1983) that internal consistency of the scale is lower when the scale is administered to obese samples. The magnitude of this difference, however, was not significant. Nonetheless, future studies should focus on exploring more closely the factors assumed to produce obese-normal weight differences in restraint scores. In summary, the results of this study support the hypothesis that restraint scores vary as a function of several subject characteristics. It is also clear that restraint scores are less reliable and generally higher in obese samples. If the construct of restraint is to be a useful tool in understanding eating patterns, future research must continue to focus on variables which affect restraint scores and must also look beyond the laboratory setting to the impact of restraint scores on actual eating behaviors.
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