Binge Eating in Females: A Population-Based Investigation"

Bonnie Bruce W. Stewart Agras

(Accepted 6 November 1991)

Four hundred fifty-five females from a community-based, randomly sampled population were interviewed by telephone to estimate the prevalence of binge eating and to describe demographic and topographical characteristics of binge eating behavior. Binge eaters were classified according to the DSM-1 1 1-R criteria for bulimia, excluding purging behavior. The estimate for subjects meeting criteria was 1.8%, while the percentage of females who met all but frequency criteria was estimated at 3.8%. The majority of binge eaters in this study was found to engage in behaviors typically associated with binge eating episodes. O n aver- age, this group of binge eaters was older and heavier than has been reported previously, which supported observed associations between binge eating and overweight in clinical populations [Telch, Agras, & Rossiter (1988). International journal of Eating Disorders, 7 , 1 15 - 1 191. 0 I992 john Wiley & Sons, Inc.

Binge eating refers to a pattern of frequently occurring eating episodes during which the individual experiences loss of control and consumes large amounts of food, fol- lowed by negative emotional consequences (Agras & Bachman, 1989; Herzog & Copeland, 1985; Pyle, Halvorson, Neuman, & Mitchell, 1986). Although this pattern of disordered eating has been most actively investigated when associated with purging, more recently the nonpurging form of the disorder has aroused interest (Marcus & Wing, 1987; Telch, Agras, & Rossiter, 1988), and tentative criteria for binge eating dis- order have been advanced (Wilson & Walsh, 1991). Of particular concern to public health is the association between binge eating disorder and obesity. It has been shown, for example, that the prevalence of binge eating increases with increasing adiposity (Telch et al., 1988), and in individuals who are already obese, binge eating has been

*This research was part of a doctoral dissertation by the first author to the University of California, Berke- ley, in partial fulfil lment of the Dr.P.H. degree in Behavioral Sciences.

Bonnie Bruce, Dr.P.H., R.D., formally a Research Assistant with the Stanford Laboratory for the Study of Behav- ioral Medicine, is a social science researcher with the Stanford Center for Research in Disease Prevention, Stanford University. W. Stewart Agras, M.D., is a Professor at the Laboratory for the Study of Behavioral Medicine, Stanford University, Stanford, California. Correspondence should be addressed to the first author at SCRDP, 1000 Welch Rd., Palo Alto, CA 94304.

International journal of Eating Disorders, Vol. 12, No. 4, 365-373 ( 1 992) 0 1992 by John Wiley & Sons, Inc. CCC 0276-3478/92/040365-09

366 Bruce and Agras

associated with increased attrition and poor treatment outcome (Marcus & Wing, 1987; Telch et al., 1988; Wilson, 1976).

The objectives of this investigation were to provide prevalence data for binge eating and to describe demographic and topographical characteristics of binge eating behav- ior in a community-based, randomly selected group of women. Females who purged or had a history of purging were excluded from analysis, since the purpose of this research was to examine exclusively the phenomenon of binge eating. Women were chosen for this initial study, since eating disorders appear to be more prevalent in females (Gross & Rosen, 1988; Ledoux, Choquet, & Martine, 1991; Pyle et al., 1986). Bulimia nervosa, for example, has been estimated between 1.5% and 2.0% in females, while it is rare in males (Agras & Bachman, 1989).

METHODS

Subjects

A total of 455 females, aged 18 through 75 years old, were sampled randomly, and were interviewed by telephone. Subjects were selected using a standard random digit dialing technique (Lavrakas, 1987) to identify households. Randomness of the study population was preserved by applying the lasthext birthday method (Aday, 1989) when there was more than one eligible female residing in the household. The subjects were from the south San Francisco Bay Area, which was known to be demographi- cally, ethnically, and economically diverse. Only English speaking females were inter- viewed, though since interpreters for other languages were not available. Telephone calls were made at varied times and on different days from September 1990, through January 1991. All responses were obtained anonymously, and informed consent was obtained verbally prior to each interview. The response rate for this investigation was 61.5%, with the majority of refusals occurring before the nature of the study was dis- closed.

MATERIALS A N D MEASURES

Survey Instrument

Based on the DSM-111-R (American Psychiatric Association, 1987) criteria for bulimia nervosa, excluding the requirement for purging behavior, a structured interview was designed to estimate the prevalence of binge eating. Questions operationalizing the DSM-111-R criteria were taken from the Stanford Eating Behaviors Questionnaire (Agras, 1987) in order to probe further into the nature of the eating disorder. The term binge eating was not used in the study instrument nor during the interview in order to obtain objective information. The interview was introduced as a study about ”women’s eating habits, dieting, and weight control behaviors.” Respondents were not told the primary purpose of the investigation, and only women who were classed initially as eating disordered were questioned further to classify their binge eating status. These subjects were then asked to describe behavioral, temporal, psychological, and histori-

Binge Eating 367

cal dimensions of their binge eating behavior. In addition, the survey instrument con- tained demographic questions, and all subjects were asked to respond to questions about restrained eating behavior using Herman and Polivy’s (1980) revised 10-item Re- straint Scale.

Classification of Binge Eaters

Subjects who affirmed that they “had ever experienced an episode of eating where they felt out of control or were unable to stop eating” and were currently experiencing these episodes were classed initially as Eating Disordered. Their classification was fur- ther refined on an individual case basis by conservative application of the DSM-111-R criteria for bulimia nervosa, excluding purging behavior. Women who met these crite- ria were labeled as being Binge Eating Disordered. Females who did not meet the twice weekly frequency criteria were classed as Binge Eaters. The remaining subjects, who met some, but not all, of the criteria for Binge Eating Disorder or Binge Eater, were designated as being Eating Disordered, Not Otherwise Specified (EDNOS).

Restrained Eating

Because a restrictive eating pattern has been associated with binge eating (Herman & Polivy, 1980), all subjects, regardless of binge eating status, were classed as restrained or unrestrained eaters, using Herman and Polivy’s revised 1980 10-item Restraint Scale. The customary cutoff score of 17 and above for a restrained classification and 16 or be- low for an unrestrained classification was used.

Body Weight

Self-reported height and weight were converted to Body Mass Index (BMI) units (weight in kilograms divided by height in meters squared). BMIs were then classified into weight classes in a similar fashion as that described by Simopoulos and Van Itallie (1984) and Van Itallie (1985) as follows: BMI = <21 (Underweight); BMI = 21-27.29 (Average Weight); BMI = 27.3-32.29 (Overweight); and a BMI = 32.3 or higher (Se- verely Overweight).

RESULTS

Representativeness and Demographics of the Sample

The demographics of this randomly sampled group of women are presented in Table 1. When compared with the 1980 United States Census Bureau data for the survey area, the subjects were representative in terms of their mean age. They were also sim- ilar in weight status to that reported by Simopoulos (1987) for the same weight and age classification. However, Asian females, Caucasian females, and females from other ethnic groups (i.e. , Native Indians, Middle Eastern, and other self-defined combina- tions) were oversampled, while Blacks and Hispanics were somewhat underrepre- sented. Overall, Caucasian women predominated, with the remaining population being composed of small proportions from all other ethnic groups. Further, more than

368 Bruce and Agras

half of these subjects were at least college graduates, whereas according to the U.S. Census Bureau (1988) for the state of California, only a third of the female population was reported to be as highly educated.

Demographics of Non-Eating Disordered and Eating Disordered Females

Table 1 shows that the distribution of demographic characteristics between non-eat- ing disordered and eating disordered samples was similar, with the exception of age and weight. The majority of women were Caucasian, married, and well educated. The mean age of subjects increased with eating disorder classification, with the average binge eating disordered woman being the oldest. The mean age of Non-Eating disor- dered women was 42 years, the groups of EDNOS and Binge Eaters both averaged 43 years, while subjects classed as being Binge Eating Disordered were about 47 years old.

An analysis of the weight classifications between the different groups of subjects showed a statistically significant difference (U = 6,560.5, p = .0001) between non-eat- ing disordered and eating disordered samples, with weight increasing progressively with binge eating status. Among all participants, the group of Binge Eating Disordered women was the heaviest, while also being conspicuously absent from the Underweight classification, thereby suggesting a possible association between weight and females with serious binge eating problems compared to those with no or lesser binge eating problems.

The mean BMI of Non-Binge Eaters (22.85, SD 3.97), the groups of EDNOS (24.76, S D 5.57), and Binge Eaters (26.21, SD 4.59) placed the average subject from each group within the Average Weight classification, while the average Binge Eating Disordered woman was classed as Overweight (30.24, S D 6.02). The data additionally showed a moderately positive association (Y = .32) between BMI and binge eating frequency for all binge eaters regardless of binge eating classification, also supporting a relationship between binge eating and weight.

Table 1. Characteristics of study population

Non- Eating

Disordered EDNOS Binge Eaters

Binge Eating

Disorder

N (%)

Mean age 42 Weight status

Underweight (BMI 148 (37.6)

Average Weight 198 (50.2)

Overweight (BMI 35 (8.9)

4 1 )

(BMI 21-27.29)

27.3- 32.29) Severely Overweight 13 (3.3)

(BMI 32.3 and >) Race

Asian 29 (7.3) Black 16 (4.0) Caucasian 326 (81.7) Hispanic 16 (4.0) Other 12 (3.0)

3Fqmmj

43

6 (21.4)

10 (35.7)

9 (32.1)

3 (10.7) zq?mj 3 (10.7) l(3.6)

23 (82.1) l(3.6)’

28 (100.0) 0 (0)

43

l(5.9)

6 (35.3)

7 (41.2)

3 (17.6)

l (5 .9)’ 0 (0)

17 (100.0)

47

0 (0)

2 (25.0)

1 (12.5)

5 (62.50) TJ-0

0 (0) l(12.5) 6 (75.0)

Binge Eating 369

Table 1. Characteristics of study population (continued)

Non- Binge Eating Binge Eating

Disordered EDNOS Eaters Disorder

N (%I N (%) N (a) N (%I EDUCATION

Not a High School Graduate 19 (4.8) 4 (13.3) 2 (11.8) 1 (12.5) High School Graduate 81 (20.4) 5 (16.7) 2 (11.8) 1 (12.5) Some College 97 (24.4) 4 (13.3) 4 (23.5) 3 (37.5) College Graduate 112 (28.1) 7 (23.3) 3 (17.6) 0 (0) Post Graduate Work 89 (22.4) 10 (33.3) 6 (35.5) 3 (37.5)

398 (100.1) m ( 9 9 . 9 ) 17 (100.0) 8 (100.0) MARITAL STATUS

Unmarried 74 (18.6) 6 (20.0) 5 (29.4) 2 (25.0) Married 242 (60.8) 20 (66.7) 8 (47.1) 5 (62.5)

Divorced 48 (12.1) 1 (3.3) 4 (23.5) 1 (12.5) Separated 9 (2.3) 1 (3.3) 0 (0) 0 (0)

Widowed 25 (6.3)' 2 (6.7) o ' (oj o ' (oj 398 (100.1) 30 (100.0) 17 (100.0) 8 (100.0)

RESTRAZNED EATING Restrained Eaters 88 (23.7) 14 (53.8) 14 (82.4) 5 (71.4) Unrestrained Eaters 283 (76.3) 12 (46.1) 3 (17.6) 2 (28.6)

371 (100.0) 26 (99.9) 17 (100.0) 7 (100.0)

Mean Restraint Score 12.6 16.9 21.4 21.1

Restrained Eating

Table 1 also presents the percentages of restrained and unrestrained eaters in each of the eating and non-eating disordered categories. Less than a fourth (23.7%) of non-eat- ing disordered females were classed as restrained eaters, whereas two thirds (66%) of all eating disordered women were also restrained eaters, with the difference in re- strained classification between these two groups being statistically significant (U-5,857, p = .0001). The findings also showed that the mean restraint scores increased with binge eating status, although there was no difference between the Binge Eating Disor- dered and Binge Eater groups on this measure.

In addition, a comparison of Restraint Scale classification with the weights of the three groups of eating disordered women indicated that more restrained eating disor- dered subjects were overweight than those who were non-eating disordered. Table 2 shows in particular that a much greater percentage of subjects with Binge Eating Dis- order were Severely Overweight than all other groups, suggesting a possible interrela- tionship between binge eating severity, a restrictive eating pattern, and weight.

Prevalence of Binge Eating

The data indicated that 1.8% of the study population were classified as being Binge Eating Disordered, while 3.8% were labeled as Binge Eaters. The remaining subjects (6.6%) were classed as EDNOS (see Table 3) .

W

U

0

Tabl

e 2.

B

inge

eat

ing

and

rest

rain

t cl

assi

ficat

ion

by w

eigh

t sta

tus

Non

-Eat

ing

Dis

orde

red

EDN

OS

Bin

ge E

ater

s B

inge

Eat

ing

Dis

orde

r

Res

trict

ed

Unr

estri

cted

R

estri

cted

U

nres

trict

ed

Res

trict

ed

Unr

estri

cted

R

estri

cted

U

nres

trict

ed

N (a

) N

(%I

N (R

) N

(%)

N (%

) N

(%

) N

(%I

N (%

)

Und

erw

eigh

t 19

(22.

1)

124

(43.

8)

2 (1

4.3)

3

(25.

0)

0 (0

) l(

33.3

) 0

(0)

0 (0

) (B

MI <

21)

Ave

rage

Wei

ght

44 (

51.2

) 13

9 (4

9.1)

4

(28.

6)

6 (5

0.0)

5

(35.

7)

l(33

.3)

0 (0

) 2

(100

.0)

fBM

I 21-

27.2

9)

OG

erw

eigh

t 15

(17.

4)

16 (5

.7)

6 (4

2.8)

3

(25.

0)

7 (5

0.0)

0

(0)

l(16

.7)

0 (0

) (B

MI 2

7.3-

32.2

9)

Seve

rely

Ove

rwei

ght

8 (9

.3)

4 (1

.4)

2 (1

4.3)

0

(0)

2 (1

4.3)

1

(33.

3)

5 (8

3.3)

0

(0)

(BM

I 32.

3 an

d >

) 86

(100

.0)

283

(100

.0)

14 (1

00.0

) 12

(100

.0)

14 (1

00.0

) 3

(99.

9)

6 (1

00.0

) 2

(100

.0)

Binge Eating

Table 3. Distribution of binge eaters

371

Count Percent

Binge Eating Disordered 8 (1.8) Binge Eaters 17 (3.8) Eating Disordered, Not - 30 - (6.6)

Otherwise Specified IEDNOS) Total Eating Disordered 55 - (12.2)

Total - 455 (100.1) 400 (87.9) Non-Eating Disordered - -

Characteristics of Binge Eating Behavior

The description of features and characteristics of binge eating behavior for the three groups of binge eaters in this study is presented in Table 4. It shows that the majority of subjects engaged in behaviors typically associated with binge eating episodes. Some two thirds of the sample ate large amounts of foods, or ate rapidly during a binge. ”Large amounts” were qualified in terms of the woman’s subjective perception. About 89% stated that they ate high calorie foods, or ate alone during their binges. Psycho- logical or emotion-based dimensions, such as feeling depressed, being bored or lonely, or experiencing food cravings, stood out as predominant binge eating triggers for more than half of these women, while feeling depressed was reported by more than three fourths. Furthermore, these types of feelings were more than twice as likely than phys- iological factors, such as hunger or prolonged dieting, to be triggers. A large propor- tion (85.5%) indicated that their binges lasted 1-2 hours or less, with the remaining subjects reporting that binges lasted longer than 2 hours. The data also showed that binge eaters consumed a variety of foods during a binge, although sweets (e.g., cakes, cookies, candy, or ice cream) were the predominant choices.

DISC U SSI 0 N

This cross-sectional study set out to estimate the prevalence of binge eating and to describe the characteristics of binge eaters in a randomly sampled group of women within a defined geographical area. The data indicated that binge eating disorder is quite prevalent in the female general population, that binge eating characteristics mir- ror previous reports, and that the results support observed associations between binge eating and overweight in clinical populations (Telch et al., 1988). In addition, these findings indicated that a higher fraction of the population met criteria for binge eating disorder, with the exception of frequency. While the latter group (Binge Eaters) were similarly restrained in their dietary habits, those with binge eating disorder were more likely to be severely overweight, suggesting that frequency of binge eating may mediate the relationship between binge eating status and overweight.

Some 8% of the overweight population in this sample met criteria for binge eating disorder. This is a lower percentage than is usually found in clinical samples of over- weight binge eaters, where between 20% and 30% of overweight individuals meet sim- ilar criteria (Gormally, Black, Daston, & Rardin, 1982; Keefe, Wyshogord, Weinberger, & Agras, 1984; Lor0 & Orleans, 1981). This suggests that there is a selective process, such that persons with binge eating disorder are more likely to seek treatment for over- weight than are overweight persons without the disorder. This overrepresentation of

3 7 2 Bruce and Agras

Table 4. Characteristic features associated with binge eating

Count Percent

Behavior during a binge (N = 55) Eats large amounts of food 38 69.1 Eats rapidly 33 60.0 Eats high calorie food 49 89.1 Eats alone 49 89.1

Binge Eating Triggers (N = 55) Depressed mood Boredom/loneliness Food cravings Hunger Period of prolonged

dieting Length of binging episode

Less than 1 hour 1 - 2 hours More than 2 hours

46 83.6 33 60.0 38 69.1 21 38.2

17 30.9

32 58.2 15 27.3 8 14.5

55 1oo.o - -

binge eaters in weight control programs may be mediated in part by their being heavier than their non-binge eating counterparts. On the other hand, the mean age of the com- munity sample meeting criteria for binge eating disorder (47 years) is very similar to the age found in clinical samples of overweight binge eaters. The characteristics of those meeting criteria for binge eating disorder are very similar to those who binge less frequently, denoted here as Binge Eaters. However, as noted above, there is a hint in these data that frequency of binge eating may be associated with degree of overweight, suggesting that some diagnostic distinction on frequency of binge eating is important. It should be noted, too, that the lower prevalence rate found in this study may be re- lated to the sampling method, since previous research has not used random sampling. In addition, published accounts have used widely varying and, in some instances, less conservative criteria for classifying binge eaters (Hawkins, Falk, & Schwartz, 1981; Jones, Doheny, Jones, & Bradley, 1986; Lor0 & Orleans, 1981).

Some limitations of this study should be recognized. First, the random digit dialing methodology employed to obtain the sample may have affected its demographic distri- bution by introducing selection bias, since information about the distribution of tele- phone lines among different ethnic groups in the local calling area was not known. Furthermore, during random sampling, females who were not interested in topics re- lated to eating habits, dieting, or weight control behaviors, or women who were overly concerned or sensitive about these subjects, may have selected themselves out. Finally, the use of telephone, rather than a direct interview, may have imposed potential limi- tations on the quality of information.

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