Dieting Behaviors and Weight Change History in

Health Psychology 1995, Vol. 14, No. 6, 548-555

Copyright 1995 by the American Psychological Association, Inc. 0278-6133/95/$3.(X)

Dieting Behaviors and Weight Change History in Female Adolescents Simone A. French, Cheryl L. Perry, Gloria R. Leon, and Jayne A. Fulkerson University of Minnesota, Minneapolis The prevalence of dieting, weight change history, and specific weight loss behaviors was examined in a population-based sample of 1,015 female 9th-12th graders. Healthy weight loss behaviors were reported much more frequently than unhealthy weight loss behaviors (e.g., healthy behaviors: exercise = 32.4%, decrease fat intake = 26.0%, reduce snacks = 25.0%, reduce kilocalorie intake = 22.4%; unhealthy behaviors: fasting = 8.1%, diet pills = 5.4%, vomiting = 4.4%). Obesity status and restrained eating scores were positively related to greater history of weight loss episodes, pounds lost, and weight fluctuations and to greater use of healthy weight loss methods and weight loss programs. Implications for public health recommendations regarding dieting and its associated behaviors in female adolescents are discussed. Key words: dieting, eating disorders, restrained eating, obesity

Dieting for weight loss or weight control is a widespread practice among female adolescents (French & Jeffery, 1994; Serdula, Collins, et al., 1993; U.S. Department of Health and Human Services [USDHHS] et al., 1989). Recent national data show that about 44% of female adolescents are trying to lose weight and that an additional 26% are trying to keep from gaining weight (Serdula, Collins, et al., 1993). Thus, more than two thirds of all female adolescents, the majority of whom are of normal weight, are actively attempting to control their weight. The health effects of dieting recently have been questioned (Brownell & Rodin, 1994; French & Jeffery, 1994). Dieting may be associated with healthy behavioral changes, such as adopting a low-fat or low-kilocalorie eating pattern, and increased physical activity (French, Jeffery, & Forster, 1994; French, Jeffery, Forster, McGovern, et al., 1994; French, Jeffery, & Wing, 1994). However, a number of unhealthy behaviors also are associated with dieting, including fasting or skipping meals; the use of diet pills, appetite suppressants, or laxatives; intentional vomiting; and binge eating (French & Jeffery, 1994; USDHHS et al., 1989; Serdula, Collins, et al., 1993). Because dieting is so prevalent among young women, an important public health objective is to better understand the behaviors associated with self-reports of "dieting" and to evaluate their health implications. This goal is particularly important because the prevalence of obesity in U.S. adolescents and adults is increasing (Gortmaker, Dietz, Sobol, &

Wehler, 1987; Kuczmarski, Flegal, Campbell, & Johnson, 1994; Serdula, Ivery, et al., 1993), and future obesity prevention efforts are likely to target behavioral changes involving eating and exercise (Dietz, 1986; Forster, Jeffery, Schmid, & Kraemer, 1988). An additional question is whether the types of dieting strategies adopted differ in normal-weight and overweight young women. An argument could be made for a greater likelihood of adopting more extreme weight loss methods in either overweight or in normal-weight women. On the one hand, weight loss can be achieved by adopting modest eating and exercise behavior changes (Brownell & Jeffery, 1987; Haddock, Shadish, Klesges, & Stein, 1994). However, overweight people may adopt more extreme dieting methods because they are further from their "ideal" weight or have failed to lose weight by means of modest eating and exercise changes. On the other hand, normal-weight women may be more likely to adopt healthy or modest dieting behaviors because they are closer to their "ideal" weights. Alternatively, they may be more likely to adopt more extreme weight loss methods to achieve a socioculturally defined attractive body weight that is lower than what would be considered biologically healthy (Garner, Garfinkel, Schwartz, & Thompson, 1980; Striegel-Moore, Silberstein, & Rodin, 1986). Independent of body weight, dieting status itself may have implications for the specific types of dieting behaviors adopted (French & Jeffery, 1994). Although previous research has shown that unhealthy dieting practices are common in young women who have eating disorders (Schlundt & Johnson, 1990), much less is known about the larger population of young women who report that they are dieting or engaging in active weight control efforts (French & Jeffery, 1994). It has been suggested that chronic weight concern and dieting ("restrained eating") often lead to problematic eating independent of actual body weight via a cyclical pattern of severe food restriction and binge eating (Herman & Polivy, 1980; Stunkard & Wadden, 1990). Thus, restrained eaters may be more likely to adopt unhealthy or extreme weight control practices, regardless of their actual body weight.

Simone A. French and Cheryl L. Perry, Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis; Gloria R. Leon and Jayne A. Fulkerson, Department of Psychology, University of Minnesota, Minneapolis. This research was supported by National Institutes of Health Grant RO1 HD24700. Correspondence concerning this article should be addressed to Simone A. French, Division of Epidemiology, School of Public Health, University of Minnesota, 1300 South Second Street, Suite 300, Minneapolis, Minnesota 55454-1015. Electronic mail may be sent to [email protected].

548

549

DIETING BEHAVIORS

The purpose of the current study was to examine the specific behavioral strategies practiced for weight control in a population-based sample of female adolescents. The prevalence of specific weight control practices according to body weight and dieting status also was studied. Finally, we examined the relationship of dieting strategies to history of weight loss to evaluate whether certain dieting behaviors would be associated with a more severe weight change and dieting history. The overall goal was to (a) determine the extent to which healthy or unhealthy behaviors are associated with reports of dieting in the general population of female adolescents and (b) examine the relationship between specific dieting behaviors and history of weight change. Method Study Population Data were collected as part of a longitudinal study on the development of eating disorders (Leon, Fulkerson, Perry, & Early-Zald, 1994). All female students attending schools in a suburban school district were surveyed (response rate = 94%). The 1,015 female students who made up the cross-sectional sample for this study were in Grades 9 through 12. The sample was 89% White, 4% other or mixed race, 3% Asian American, and less than 1% each American Indian, African American, Mexican American, or Puerto Rican. According to student reports, 52% of the fathers and 33% of the mothers held executive, administrative, or professional occupations.

Procedure Research assistants administered a questionnaire that included the measures described next during the students' social studies classes. A makeup testing day was included to collect data from students who had been absent. Private height and weight measurements were conducted by the research assistants.

Measures Dieting in the past year. The prevalence of dieting in the past year was measured with the question, "In the past year, have you tried to lose weight?" (yes or no). Specific dieting behaviors. The use of 24 specific weight loss methods was assessed using a 24-item list in which students checked methods that they had used during the past year to lose weight (see Table 1). Principal-components analysis was used to group these dieting behaviors into meaningful categories for further examination. Three factors were identified on the basis of examination of item loadings, scree plot, and eigenvalues (Harmon, 1976; Thurstone, 1947). The Healthy Weight Loss Methods factor was composed of 11 items reflecting what would be considered healthy eating and exercise behaviors for weight loss: kilocalorie reduction, increased exercise, increased fruit and vegetable intake, eliminating snacks, decreasing fat intake, eliminating sweets, reducing the amount of food consumed, changing the type of food eaten, eating less meat, eating less high-carbohydrate food, and eating low-kilocalorie foods. The Unhealthy Weight Loss Methods factor was made up of eight items reflecting unhealthy weight control practices such as fasting, skipping meals, increasing the number of cigarettes smoked, laxative use, diuretic use, appetite suppressant use, diet pill use, or vomiting. The Weight Loss Group factor consisted of two items: attending a diet center where food was provided and attending a weight loss group in which food was not provided. Item loadings ranged from 0.39 to 0.83

Table 1 Means, Standard Deviations, Percentages, and Numbers for Measures of Dieting, Weight Change History, and Weight Loss Methods Among 1,015 Female Adolescents Variable Dieting and weight change history Body mass index (kg/m2) Perceived maximum overweight (Ib) Intentional weight loss Episodes Pounds Restrained Eating Scale score Dieted in past year (% yes) Weight fluctuations >; 8 Ib in past year (% yes) Weight gain > 8 Ib in past year (%yes) Weight loss > 8 Ib in past year (% yes) Binge eating in past year (% yes) History of anorexia History of bulimia Weight loss methods (% yes) Increase exercise Increase fruit and vegetable intake Decrease fat intake Eliminate snacking Eliminate sweets and junk food Reduce kilocalories Reduce amount of food Change food type Eat low-calorie foods Skip meals Eat less meat Fast Diet pills Vomiting Eat less high-carbohydrate food Appetite suppressants Liquid diets Drink less alcohol Increase cigarettes smoked3 Laxatives or enemas Diet center with food Weight loss group Diuretics Other Total number of methods a

M

SD

22.1

3.9

8.2

6.8

2.5 24.1 11.3

4.4 56.6 5.8

4.3

41.4

420

18.9

173

7.0

61

9.9

90

11.9 1.9 1.6

109 18 15

32.4

329

26.9 26.0 25.0 24.2 22.4 21.9 21.8 14.3 11.6 11.2 8.1 5.4 4.4 4.9 3.3 3.2 2.7 15.4 1.6 1.5 1.9 1.0 0.9 2.8

273 264 254 246 227 222 221 145 118 114 82 55 45 50 34 32 27 25 16 15 19 10 9

Among current smokers (n = 162).

(M = 0.71, SD = 0.14). Alternative factor loadings ranged from 0.01 to 0.42 (M = 0.13, SZ> = 0.09). Eigenvalues for the Healthy, Unhealthy, and Weight Loss Program factors were 8.34, 2.43, and 1.59, respectively. Liquid diets, decreasing alcohol intake, and "other" weight loss methods did not load on any factor and were dropped from further consideration. Factor-based scores were created by summing the number of strategies endorsed for each factor. Descriptive statistics for the scales are as follows: (a) mean healthy weight loss = 2.3 (SD = 3.5, range = 0-11; Cronbach's a = 0.93); (b) mean unhealthy weight loss = 0.4 (SD = 1.1, range = 0-8; Cronbach's ct = 0.81); (c) mean weight loss programs = 0.03 (SD = 0.2, range = 0-2; Cronbach's a = 0.74). Restrained eating. Chronic dieting and weight concern were assessed using the Restrained Eating Scale (RES; Herman & Polivy, 1980). The 10-item scale focuses on weight concern, weight fluctua-

550

FRENCH, PERRY, LEON, AND FULKERSON

tions, and emotional reactions to eating and weight. The scale has high reliability and is related to eating patterns in laboratory settings (Heatherton, Herman, Polivy, King, & McGree, 1988; Ruderman, 1986). However, it is not usually related to actual body weight changes over time or to food intake in naturalistic settings (French & Jeffery, 1994; Klesges, Klem, Epkins, & Klesges, 1991; Pirke & Laessle, 1993; however, see Klesges, Isbell, & Klesges, 1992). Binge eating. Binge eating during the past year was assessed with the question, "In the past year, have there been times when you hinged or ate an amount of food that is definitely larger than what most people would eat during a similar period of time?" (yes or no). History of anorexia nervosa or bulimia. A history of anorexia or bulimia was assessed with two questions: "Have you ever been diagnosed by a psychologist, psychiatrist, or other doctor as suffering from anorexia nervosa [bulimia or bulimia nervosa]?" (yes or no). Weight fluctuations, gains, and losses. These variables were assessed with the following questions: (a) "In the past year, did your weight go up and down eight or more pounds at a time at least twice?"; (b) "In the past year, were there times when you lost eight pounds or more at a time, but did not gain back the weight?"; and (c) "In the past year, were there times when you gained eight pounds or more at a time but did not get back later to your previous weight?" (yes or no). Perceived maximum overweight. Lifetime maximum number of pounds over desired weight was calculated on the basis of responses to one of the items on the RES: "How many pounds over your desired weight were you when you weighed the most you've ever weighed?" The total number of pounds was calculated by assigning the midpoint of the range for the response option categories (i.e., 0-5 Ib [0-2.25 kg] = 2.5 Ib [1.125 kg]; 6-10 Ib [2.7-4.5 kg] = 8 Ib [3.6 kg]; 11-20 Ib [4.95-9.00 kg] = 15.5 Ib [6.975 kg]; 21 + Ib [9.45+ kg] = 21 Ib [9.45 kg]; and "I have always weighed less than my desired weight" = 0 Ib). Intentional weight loss. History of intentional weight loss was assessed with the question, "Check the number of times in your life you have on purpose lost the number of pounds shown below (e.g., through diet, exercise, a formal weight control program, etc.). Do not count weight loss because of illness or surgery." Five questions were then completed in which students marked the number of times they had intentionally lost 5-9 Ib (2.25-4.05 kg), 10-14 Ib (4.5-6.3 kg), 15-19 Ib (6.75-8.55 kg), 20-24 Ib (9.0-10.8 kg), and 25+ Ib (11.25 + kg). Response options were never, 1-2 times, 3-5 times, 6-10 times, and more than 10 times. Intentional weight loss episodes were calculated by assigning the midpoint of each response option category (e.g., never = 0, 1-2 times = 1.5, 3-5 times = 4, 6-10 times = 8, and more than 10 times = 10) and summing the total number of episodes across weight loss amounts. Intentional weight loss pounds were calculated in a similar fashion, assigning the midpoint of the range for each weight loss amount (e.g., 5-9 [2.25^.05 kg] = 7, etc.) and multiplying by the number of weight loss episodes reported for each amount. Body mass index. Body weight was measured using an electronic scale calibrated to the nearest half pound. Height was measured with a wall-mounted tape measure. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared.

Statistical Analyses All analyses were conducted using the SAS statistical analysis software package (SAS Institute, 1989). Restrained eating groups were created by dividing RES scores into tertiles. Cutpoints for the RES were as follows: low = 0-8, middle = 9-13, and high = 14-18. Weight categories were based on the recommendations of the Expert Committee on Clinical Guidelines for Overweight in Adolescent Preventive Services established as an advisory group to two national health initiatives (Himes & Dietz, 1994). The cutpoint for normal weight for Grades 9 and 10 was a BMI less than 24 kg/m2; for Grades

11 and 12, the BMI was less than 25 kg/m2. The cutpoint for at risk for being overweight for Grades 9 and 10 was 24 kg/m2 z BMI < 28.5 kg/m2; for Grades 11 and 12 it was 25 kg/m 2 29.5 kg/m2. PROC GLM/MANOVA was used to evaluate differences between the body weight categories or RES tertiles in weight history variables and weight loss methods. In the first set of analyses, body weight category was the independent variable, school grade level was the covariate, and the weight history measures or weight loss methods were the dependent variables. The latter dependent variables were dichotomized (any vs. none; in the past year) because of their skewed distribution for which a successful transformation was not identified. In the second set of analyses, tertile of RES was the independent variable, school grade level and body weight category were covariates, and the weight history measures were the dependent variables. A second set of analyses was run that included the interaction term between RES and body weight category. Significant interaction effects indicated that the relationship between RES and weight change history, or weight loss methods, differed among the body weight categories. A second set of GLM/MANOVA analyses was conducted to evaluate the relationship between specific dieting methods and weight change history. Individuals were classified as follows: (a) used only healthy methods, (b) used both healthy and unhealthy methods, or (c) used no methods. No category was created for "used only unhealthy methods" because only 2 participants would have been so classified. These 2 individuals were grouped with the healthy and unhealthy methods category for analysis. This three-level dieting methods variable was then entered as an independent variable in the analysis of weight history variables. Use of weight loss programs was examined as an independent variable in a separate analysis of the weight change history dependent variables. Grade in school and body weight category were covariates, and the weight change history variables were grouped dependent variables in these analyses.

Results

Prevalence of Dieting, Weight Change History, and Weight Loss Methods Eighty-one percent of the sample were normal weight, 12.5% were at risk for being overweight, and 6.2% were overweight. Fifty-six percent of the sample reported at least one intentional weight loss episode of 5+ Ib (2.3+ kg) at some point during their lifetime, an average of 2.5 weight loss episodes, and an average total lifetime weight loss of 24.1 Ib (10.8 kg; see Table 1). Although 41% reported dieting during the past year, only 9.9% reported a weight loss of 8+ Ib (3.6+ kg), and only 18.9% reported weight fluctuations of this amount or more during the past year. Sixty-three percent of the participants in the sample reported using no weight loss methods during the past year, 21.5% reported using only healthy weight loss methods, and 15.2% reported using both healthy and unhealthy weight loss methods. Increased exercise, increased fruit and vegetable intake, decreased fat intake, elimination of snacking, and elimination of sweets or "junk food" were the most frequently reported dieting behaviors. Dieting behaviors that would be considered unhealthy or harmful were not frequently endorsed. For example, 4.4% reported using vomiting, 5.4% diet pills, 3.3% appetite suppressants, 1.6% laxatives or enemas,

551

DIETING BEHAVIORS

and 1.0% diuretics for weight loss. The use of professionally supervised weight loss groups (1.9%) or diet centers (1.5%) was also infrequent (a total of 24 participants [2.4%] reported using either of these for weight loss). Among the 162 current smokers, 15.4% reported increasing the number of cigarettes smoked as a weight loss method. Body Weight Category, Weight Change History, and Weight Loss Methods Intentional weight loss episodes, total number of pounds intentionally lost, weight fluctuations, and losses and gains of 8+ Ib (3.6+ kg) were positively related to body weight category (Wilks's X = .55),F(22,1558) = 24.78, p < .0001. Overweight participants reported a lifetime total of 93.2 Ib (42.4 kg) intentionally lost, and 6.9 intentional weight loss episodes, compared with 15.2 Ib (6.9 kg) and 1.8 episodes among those of normal weight (see Table 2). About three times as many overweight participants reported weight fluctuations of 8+ Ib (3.6+ kg) during the past year compared with normal-weight participants (37.5% vs. 13.1%, respectively). Weight gains, but not weight losses, were much more prevalent in overweight

compared with normal-weight participants (17.9% vs. 4.5%, respectively). Sixty-seven percent of the overweight participants had dieted to lose weight during the past year compared with 41.6% of the normal-weight participants. Body weight category was positively associated with the use of healthy and unhealthy dieting methods and with the use of weight loss programs during the past year (Wilks's X = .94), F(6,1852) = 9.94, p < .0001 (see Table 2). On average, 60.7% of overweight participants reported using healthy weight loss methods compared with 34.5% of normal-weight participants. Unhealthy weight control practices were weakly related to body weight category (20.6% in overweight vs. 14.2% in normal-weight participants). Overweight participants were much more likely than normal-weight participants to report attending a diet center or weight loss group (10.4% vs. 1.0%, respectively). Restrained Eating, Weight Change History, and Weight Loss Methods Because a major component of the RES measures weight fluctuations (Heatherton, Polivy, & Herman, 1991; Ruderman,

Table 2 Adjusted Means, Standard Errors, Numbers, and Percentages for Measures of Dieting, Weight Change History, and Weight Loss Methods by Body Weight Category Among 1,015 Female Adolescents M

SE

n

%

759 81.3 No. of participants Dieting and weight change history 20.7 O.la Body mass index Perceived maximum overweight 6.0 0.2a Intentional weight loss 1.8 0.2a Episodes Pounds 15.2 2.1a Restrained Eating Scale score 10.1 0.2a Dieted in past year (% yes) 41. 6a Weightfluctuations>8 Ib in past year (% yes) 13.1a Weight gain > 8 Ib in past year (% yes) 4.5a Weight loss > 8 Ib in past year (% yes) 8.4a Binge eating in past year (% yes) 10.8 History of anorexia 16 1.7 History of bulimia 9 1.1 Weight loss methods Healthy (% any) 34.5a Unhealthy (% any) 14.2a Weight loss programs (%

any)

Overweight

At risk

Normal

Variable

1.0,

M

SE

n

%

M

SE

117 12.5

n

%

58

6.2

P

26.2 0.2b

32.9 0.3C

.0001

15.2 0.5b

18.0 0.7C

.0001

4.4 0.4b 43.2 5.4b

6.9 0.6C 93.2 7.6C

.0001 .0001

14.5 0.5

14.8 0.8

.0001

0 2

70.0

67.0

.0001

37.9

37.5

.0001

13.6

17.9

.0001

19.5b

10.1a,b

.003

17.7 0 2.0

.07 .28 .78

54.8 22.2b

60.7

.0001

20.6,,b

.05

8.6

10.4

.0001

17.5 0 1.9

0 2

Note. Different subscripts indicate significantly different means by post hoc comparisons (p < .05). Means and standard errors were adjusted for grade in school. Normal weight = a body mass index (BMI) < 24 kg/m2 for Grades 9 and 10 and < 25 kg/m2 for Grades 11 and 12. At risk = 24 kg/m 2 < BMI < 28.5 kg/m2 for Grades 9 and 10 and 25 kg/m 2 s BMI < 29.5 kg/m 2 for Grades 11 and 12). Overweight = BMI > 28.5 kg/m 2 for Grades 9 and 10 and BMI > 29.5 kg/m 2 for Grades 11 and 12.


552

1986), it is not surprising that independent of body weight category, restrained eating was consistently associated with greater history of weight fluctuations and intentional weight loss (see Table 3; Wilks's \ = .49), F(20, 1556) = 33.40, p < .0001. High-RES participants reported a lifetime total of 4.7 intentional weight loss episodes and 46.5 Ib (21.1 kg) intentionally lost, whereas low-RES participants reported 1.0 weight loss episodes and 11.6 Ib (5.22 kg) intentionally lost. About six times as many high-RES than low-RES participants reported weight fluctuations, losses, or gains of 8+ Ib (3.6+ kg) during the past year. Of the 18 participants who reported a history of anorexia nervosa, 12, 5, and 1 were in the high-, middle-, and low-RES groups, respectively. A history of bulimia was reported by 15 participants, 14 in the high-RES group and 1 in the middle-RES group. RES was significantly positively associated with frequency of use of all dieting behaviors, independent of body weight category (Wilks's X = .76), F(6, 1834) = 45.6, p < .0001 (see Table 3). Sixty-six percent of high-RES participants reported using healthy weight loss methods, compared with 14.2% of low-RES participants. High-RES participants were also more likely to report using unhealthy weight control practices

(37.4% in high RES vs. 1.6% in low RES). Furthermore, high-RES participants were more likely than low-RES participants to have used a weight loss program in the past year, after adjusting for body weight category (5.9% vs. 1.4%, respectively). A significant interaction between RES and body weight category was observed for weight change history (Wilks's X = .87), F(40,2936.77) = 2.75, p < .0001. Significant univariate effects showed that RES scores were positively linearly related to intentional weight loss episodes and pounds lost in normal-weight and at risk for overweight participants. In overweight participants, however, intentional weight loss episodes and pounds were dramatically higher in high-RES compared with middle- or low-RES participants (data not shown). Differences in perceived maximum overweight between low-RES and middle-RES participants were greater among overweight and at-risk than in normal-weight participants. Among low-RES participants, those at risk for overweight were more likely to have dieted in the past year compared with overweight or normal-weight participants. Although the overall test of the RES x Body Weight Category

Table 3 Adjusted Means, Standard Errors, Percentages, and Numbers for Measures of Dieting, Weight Change History, and Weight Loss Methods by Restrained Eating Score Among 1,015 Female Adolescents Restrained Eating Scale score

Low Variable

M

SE

n

High

Middle %

M

SE

n

%

No. of participants 342 36.1 301 31.8 Dieting and weight change history Body mass index3 (kg/m2) 20.4 0.2a 22.6 0.2b Perceived maximum overweight (Ib) 4.3 0.3a 8.0 0.3b Intentional weight loss Episodes 2.0 0.2b 1.0 0.2a Pounds 16.2 3.3 11.6 3.1 Restrained eating 5.4 O.la 11.0 O.lb Dieted in past year (% yes) 13.8a 52.2b Weight fluctuations > 8 Ib in past year (% yes) 6.9, 15.7b Weight gain a 8 Ib in past year (% yes) 1.6 4.9 Weight loss s 8 Ib in past year (% yes) 3.4 7.4 Binge eating in past year 4.7 (%yes) 8.5 History of anorexia 1 0 5 1.2 History of bulimia 0 0 1 0.4 Weight loss methods Healthy (% any) 14.2a 39.3b Unhealthy (% any) 1.6. 10.1b Weight loss programs (% any) 1.4 0.6

M

SE

n

%

p

305 32.2

23.7 0.2c

.0001

12.4 0.3C

.0001

4.7 0.3C 46.5 3.4a 18.0 O.lc

.0001 .0001 .0001

82.2C .0001 33.5C .0001 14.3a .0001

20.5a .0001 12 14

24.8. .0001 3.3a .006 3.7a .0004

66.8C .0001 37.4C .0001 5.9a .0001

Note. Means and standard errors are adjusted for grade in school and body weight category. Different subscripts indicate significantly different means by post hoc comparisons (p < .05). "Adjusted only for grade in school.

553

DIETING BEHAVIORS

ing intensity of weight loss methods: 21.8 kg/m2 in the no weight loss methods group, 23.0 kg/m2 in the only healthy methods group, 22.3 kg/m2 in the healthy and unhealthy methods group, and 26.6 kg/m2 in the weight loss programs group versus 22.0 kg/m2 in those who did not use weight loss programs.

interaction for weight loss methods was statistically significant, none of the univariate tests reached statistical significance. Weight Loss Methods and Weight Change History The use of only healthy or both healthy and unhealthy weight loss strategies (Wilks's \ = .50), F(22, 1554) = 29.26, p < .0001, and the use of weight loss programs (Wilks's X = .85), F(ll, 778) = 12.66, p < .0001, were positively associated with dieting and weight change history (see Table 4). Perhaps most interesting is that those who used no weight control practices or only healthy weight control practices had the least severe dieting and weight loss history, whereas those who used both healthy and unhealthy or weight loss programs had the most severe dieting and weight loss history. For example, the number of pounds intentionally lost among those using no weight loss methods was 15.5 Ib (7.0 kg). Those using only healthy weight loss strategies had intentionally lost 25.0 Ib (11.3 kg) compared with 51.9 Ib (23.4 kg) and 144.4 Ib (65.0 kg) in those using both healthy and unhealthy weight loss strategies or weight loss programs, respectively. Consistent with this, the number of intentional weight loss episodes reported was 1.5, 2.7, 5.4, and 11.6 among those reporting no weight loss methods, only healthy weight loss methods, both healthy and unhealthy strategies, and weight loss programs, respectively. Similarly, weight fluctuations, weight gains, weight losses, and binge eating were more frequently reported by those who had used weight loss programs or unhealthy dieting practices in the past year. BMI was generally positively associated with increas-

Discussion The purpose of our study was to document the prevalence of specific dieting behaviors in a population-based sample of female adolescents and to examine differences in these practices by BMI and restrained eating status. Results show that the majority of participants reported what would be considered healthy eating and exercise behavior changes to lose weight. Increased exercise, eliminating snacking and sweets, eating less food and eating low-calorie foods were strategies reported most frequently. Although 41% of the participants reported dieting in the past year, only about 10% reported a modest weight loss of 8+ Ib (3.6+ kg). These findings suggest that the majority of female adolescents who diet adopt what would be considered healthful eating and exercise behaviors that do not result in drastic weight changes. These findings are consistent with results of the National Adolescent Student Health Survey (USDHHS et al., 1989), in which a national sample of 8th- and lOth-grade female students reported making what would be considered healthy or appropriate eating and exercise behavior changes for weight loss. Although the absolute rates of dieting and specific weight

Table 4 Adjusted Means, Standard Errors, Numbers, and Percentages for Measures of Dieting and Weight Change History Among Female Adolscents Using Different Weight Loss Methods

Variable

M

SE

n

%

M

SE

n

Weight loss group

Healthy an rf unhealthy met hods

Only healthy methods

No weight loss methods

%

No. of participants 641 63.2 218 21.5 21.8 O.la 23.0 O.lb Body mass index (kg/m2) Perceived maximum overweight 6.5 0.2a 9.5 0.4b (Ib) Intentional weight loss 1.5 0.2a 2.7 0.3b Episodes Pounds 15.5 2.4a 25.0 3.8b Restrained Eating Scale score 10.5 0.3a 14.5 0.4b Dieted in past year (% yes) 20.4a 78.4b Weight fluctuations £: 8 Ib in past year (% yes) 14.0 17.0 Weight gain s 8 Ib in past year (% yes) 2.9a 8.6b Weight loss £ 8 Ib in past year (% yes) 6.3 11.0 Binge eating in past year (% yes) 5.3a 15.5b History of anorexia 5 0.3 3 1.8 History of bulimia 3 0.5 1 0.4

M

SE

n

%

154

15.2

Yes

No

M

SE

n

%

M

SE

991 97.6

22.3 0.2C

22.0 0.1

26.6

0.8

11.1 0.4C

7.9 0.2

12.1

1.3

5.4 0.3C 51.9 4.6C 17.8 0.5C

2.2 0.1 20.9 1.8 10.8 0.2

n

%

24

2.4

11.6 0.9 144.4 11.9 17.9 1.2

95.6C

46.0

84.2

33.5a

17.3

42.7

17.3C

6.0

27.0

9.5

29.1 40.1 2 11.7 2 5.0

21.4a 32.2C 10a 4.7 ll a 5.4

11.4 16 13

1.1 1.2

Note. Means and percentages were adjusted for grade in school and body weight category. Body mass index was adjusted only for grade in school. All/? values less than .01 for multivariate analysis of variance (MANOVA) univariate comparisons between no weight loss methods, only healthy methods, and both healthy and unhealthy methods. All/; values less than .01 for MANOVA univariate comparisons for weight loss programs (yes or no), except history of bulimia (p < .16, ns). Different subscripts indicate significantly different means by post hoc comparisons (p < .05). The use of weight loss groups was examined in a separate analysis from the no weight loss methods, only healthy weight loss methods, and healthy and unhealthy weight loss methods. Two individuals who used only unhealthy weight loss methods are included in the Healthy and unhealthy methods column.

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loss practices were higher in the USDHHS et al. (1989) study than in the current study (e.g., eating less food: 57.1% vs. 21.9%, respectively), the overall ordering of specific behaviors was similar, with healthier behaviors being more prevalent than unhealthy ones. Some discrepancies, however, included the reported use of fasting (32.5% vs. 8.1%, respectively; skipping meals, 45.2% vs. 11.6%, respectively; diet pill use, 11.3% vs. 5.4% respectively; and vomiting, 7.6% vs. 4.4%, respectively). Discrepancies between surveys in absolute prevalence are difficult to interpret and may be due to factors such as differences in question wording, time frame specification for the behavior (e.g., dieting in the past year vs. time frame unspecified), or the population surveyed. Higher rates of unhealthy weight control practices in the USDHHS et al. (1989) study might have been due to the more heterogeneous national sample in terms of socioeconomic status (SES). It is possible that upper middle SES females are more likely to adopt healthier eating and exercise behaviors and are less likely to engage in unhealthy weight control practices than those in lower SES groups. This hypothesis, as well as the previously mentioned methodological issues, warrants further study. RES scores were associated with the use of both unhealthy and healthy weight loss methods. These findings were consistent and striking even after adjustment for body weight category. Although the effects of body weight and restrained eating were difficult to separate because the two were confounded (r = .36,p < .0001, in the current study), the extreme weight concern or "unsuccessful dieting" reflected in high RES scores might have been more closely linked to unhealthy eating practices than was BMI per se (Heatherton et al., 1988). The extreme weight concerns of the high restrained eaters, regardless of their actual body weight, might have been less "realistic" than those of the overweight participants, whose concerns might have been more directly linked to their higher actual body weight. These findings imply that dieting behaviors among overweight female adolescents may not necessarily place them at risk for developing an eating disorder. Rather, extremely high levels of weight concern characteristic of "restrained eaters" in young women of any body weight may place them at risk for more pathological eating-disordered attitudes and behaviors. Thus, restrained eating, not necessarily obesity itself, may be a better predictor of future eating problems. Although only 24 participants reported using weight loss programs, these young women were much heavier than those not using weight loss programs (26.6 kg/m2 vs. 22.0 kg/m2, respectively). Results also show a more severe dieting and weight loss history among the group who reported using weight loss programs. These findings are consistent with data on adults that suggest that those who enroll in weight loss programs may represent the most severe cases and may be more resistant to successful treatment (Brownell & Jeffery, 1987; Haddock et al., 1994; Schachter, 1982; Serdula, Ivery, et al., 1993). Female adolescents who have participated in a weight loss program may represent a group in need of special attention regarding weight loss issues. A point worth considering is the appropriateness or desirability of the high prevalence of weight control attempts, healthy

or unhealthy, in a population in whom the majority of "dieters" are of normal weight. Although attention to healthy eating and exercise behaviors is a desirable individual and public health objective, even among those without a weight problem, caution is warranted in preventing the attention from developing into extreme preoccupation or unrealistic concern, which is perhaps best reflected in highly restrained eaters. An overemphasis or overvaluation on body weight, eating, or exercise may be linked to future eating pathology. Thus, a balance is needed between attention to healthy eating and exercise behaviors for individual weight control and populationwide prevention of obesity, on the one hand, and the sociocultural valuation of extremely lean body weights for women, on the other hand. Some strengths of the current study include its large, population-based sample and the specific and detailed measures of dieting behaviors and weight loss history. A limitation that our study shares with most population-based epidemiological surveys is its reliance on self-report data. However, indirect validity for the weight loss methods and weight loss history measures can be inferred from their correlations in expected directions with validated measures of dieting (e.g., the RES) and body weight category. Furthermore, in the current study, the reported use of healthy and unhealthy weight control methods were significantly related to higher scores on Eating Disorder Inventory subscales, higher levels of high-intensity physical activity, and lower consumption of high-fat foods; the use of weight loss programs was associated with higher consumption of low-fat foods (data not shown). These findings suggest that self-reported dieting behaviors are related to eating and exercise patterns consistent with reports of dieting. A second limitation is the sample homogeneity with respect to SES and race and ethnicity. Both the prevalence of unhealthy dieting behaviors, and their relationship to body weight category or dieting status, may differ according to SES or racial or ethnic identification (Serdula, Collins, et al., 1993; Story, French, Resnick, & Blum, in press). Further research is needed to examine sociodemographic differences in dieting behaviors. In conclusion, these findings suggest that the majority of female adolescents who diet adopt what would be considered healthy behavioral changes in an effort to control their weight. These findings are somewhat reassuring in interpreting the survey data indicating that 70% of young women are trying to control their weight (USDHHS et al., 1989; Serdula, Collins, et al., 1993). However, these findings also suggest that although attention to healthy eating and exercise behaviors is desirable, caution must be observed to ensure that healthy attention to weight-related behaviors does not develop into extreme or unrealistic weight concerns or excessively lean body weight standards.

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