Weight Control Practices of U.S. Adolescents and Adults

Methods

Adolescents

The national school-based Youth Risk Behavior Survey is used to monitor the prevalence of health risk behaviors among high school students [2, 3]. The 1990 national school-based Youth Risk Behavioral Survey used a self-administered, 75-item questionnaire given within one class period during the spring. Students from public and private schools were selected using a three-stage cluster design to obtain a sample of students in grades 9 through 12 that was representative of the 50 states, the District of Columbia, and the Virgin Islands. Schools with a high proportion of black and Hispanic students were oversampled. The response rate for schools was 74% (124 of 168 schools), and that for students was 87% (11 631 of 13 402 students). We excluded 164 students because of inadequate information on demographics or weight control practices. The final sample included was 11 467 students. Our analysis weighted all responses to compensate for the sampling design.

Respondents were asked the following questions about weight perception and weight control practices:

1) Do you think of yourself as too thin (underweight), about the right weight, or too fat (overweight)?

2) Which of the following are you doing about your weight? Not trying to do anything about weight, trying to lose weight, trying to keep from gaining more weight, or trying to gain more weight?

3) During the past 7 days, how many meals did you skip to try to lose weight or to keep from gaining weight? None, 1 or 2 meals, 3 to 6 meals, 7 to 14 meals, 15 or more meals.

4) During the past 7 days, how many times did you take a diet pill, vomit on purpose, or exercise to try to lose weight or keep from gaining weight? Never done this; have done this but not in the past 7 days, 1 or 2 times, 3 to 6 times, 7 to 14 times, 15 or more times.

For the purpose of analysis, we defined ever use of these specific weight control methods to include one or more times in the past 7 days or have done this but not in the past 7 days.

Adults

Data for the Behavioral Risk Factor Surveillance System were collected by state health departments in collaboration with the Centers for Disease Control. The primary purpose of this system was to provide state-specific estimates of behaviors that relate to the leading causes of death among U.S. adults. In each participating state, an independent probability sample of adult residents with telephones was selected using a multistage cluster sampling design based on the Waksberg method [4]. All states used an identical core questionnaire administered by trained interviewers. Interviews lasted approximately 25 minutes [5].

During the interview, all respondents were asked, Are you now trying to lose weight? Those who answered no were asked, Are you now trying to maintain your weight; that is, keep from gaining weight? After the questions on weight control practices, all respondents were asked, Do you now consider yourself to be overweight, underweight, or about average? Questions about self-reported weight and height were asked at the end of the interview [6].

During 1989, 38 states and the District of Columbia collected data. One state was excluded from analysis because information was not collected on weight control practices. We limited our analysis to the 64 311 persons who were not pregnant at the time of the interview. We excluded an additional 3 450 persons because of inadequate information on sociodemographic status, weight perception, weight control goals, or current weight and height. Our final sample included 60 861 participants. The median response rate for the states was 82%. We directly age-standardized all prevalence estimates using the age distribution of the total Behavioral Risk Factor Surveillance System sample as the referent population. We categorized respondents according to three categories of body mass index based on the National Health and Examination Survey (NHANES) II reference sample for persons 20 to 29 years old (< 85th percentile, 85th to < 95th percentile, and 95th percentile) [7].

Results

Adolescents

Among All Students

The Youth Risk Behavior Survey found substantial differences in weight perception between male and female students. Female students were more than twice as likely as male students to consider themselves to be too fat (34% and 15%, respectively) and were less than half as likely to consider themselves to be too thin (7% and 16%, respectively). Among female students, 37% of both whites and Hispanics considered themselves to be too fat compared with 25% among blacks. Among male students, whites and Hispanics were also more likely than blacks to consider themselves to be overweight (16%, 15%, and 8%, respectively).

Among female students, 44% reported that they were trying to lose weight, 26% were trying to keep from gaining weight, 7% were trying to gain weight, and 23% were not trying to do anything about their weight (Table 1). Among male students, 15% reported that they were trying to lose weight, 15% were trying to keep from gaining weight, 26% were trying to gain weight, and 44% were not trying to do anything about their weight. Among both male and female students, attempts to lose weight were unrelated to grade level and were most strongly associated with weight perception, although less so among blacks. The students reported using the following methods to lose or maintain weight in the 7 days preceding the survey: exercising (51% of female students and 30% of male students), skipping meals (49% and 18%, respectively), using diet pills (4% and 2%, respectively), and vomiting (3% and 1%, respectively). In general, the percentage of students who reported ever having used these methods was much higher: exercising (80% and 44%, respectively), using diet pills (21% and 5%, respectively), and vomiting (14% and 4%, respectively).

Among Students Trying To Lose Weight

Among both sexes, exercise and skipping meals were much more frequently used to lose weight than were either diet pills or vomiting (Table 2). Exercising once a day or more as a means of weight control was more frequent among male students (29% of male students compared with 19% of female students), whereas skipping meals at least daily was more common among female students (17% of female students compared with 11% of male students).

Compared with female students trying to lose weight, male students were slightly more likely to use exercise and less likely to skip meals. Among female students trying to lose weight, use of exercise in the previous week was somewhat higher among those in their first 2 years of high school (see Table 2). Use of other methods did not vary consistently by grade level. White students were most likely and black students were least likely to use exercise for weight control.

Among male students who were trying to lose weight, use of diet pills and exercise increased with increasing grade level; however, use of other methods did not vary consistently by grade. Compared with white students, black students were somewhat less likely to report exercise as a means of weight control.

Adults

Women were more likely than men to consider themselves to be overweight (38% compared with 28%). White, black, and Hispanic women were equally likely to consider themselves overweight. Among men, whites and Hispanics were somewhat more likely than blacks to consider themselves overweight (29%, 28%, and 23%, respectively).

Among women, 38% reported that they were trying to lose weight at the time of the survey, 28% were trying to maintain weight, and 33% were doing neither. Among men, 24% reported that they were trying to lose weight, 28% were trying to maintain weight, and 48% were doing neither.

Among both sexes, the prevalence of attempts at weight loss was similar among all participants up to 59 years old but decreased substantially at older ages (Table 3). Among women, the prevalence of attempts at weight loss was similar across ethnic and education groups. Among men, Hispanics and the more educated were more likely to report trying to lose weight. Among both sexes, the practice of trying to lose weight was strongly associated with body mass index and weight perception.

Discussion

Attempts at weight control are very prevalent among both adolescents and adults in the United States. Among high school students, 44% of females and 15% of males reported that they were trying to lose weight. An additional 26% of female students and 15% of male students reported that they were trying to keep from gaining weight. Among adults, 38% of women and 24% of men reported that they were trying to lose weight, whereas 28% of both sexes reported that they were trying to maintain weight.

The prevalence of weight loss attempts in the Youth Risk Behavior Survey was intermediate between prevalences of dieting observed in two earlier national surveys of college and high school students. A national probability telephone survey of college students conducted in 1987 showed that 21% of female students and 8% of male students reported being on a diet at the time of the survey [8]. In contrast, the 1988 National Adolescent and School Health Survey of 8th- and 10th-grade students indicated that 61% of female students and 28% of male students reported dieting during the previous year [9]. Although these estimates are higher than those from the Youth Risk Behavior Survey, direct comparison is difficult because the referent period was longer (during the last year) and because the question was about dieting (rather than about the more general intent to lose weight).

In the 1985 National Health Interview Survey, 44% of women and 25% of men reported a current attempt to lose weight [10]. These estimates are similar to those obtained from the Behavioral Risk Factor Surveillance System. As expected, a higher prevalence of ever having dieted to lose weight was seen in a population-based survey of adults in the Minneapolis-St. Paul metropolitan area conducted in 1980 and 1981. In this survey, 72% of women and 44% of men reported ever dieting [11].

Desire for thinness can lead to various unsound weight-loss methods. About one quarter of female high school students and 20% of adult women who considered themselves to be the right weight reported that they were nonetheless trying to lose weight. Although use of vomiting or diet pills in the past week was reported by 4% or fewer of female high school students, a much higher proportion reported ever having used these methods (14% for vomiting and 21% for diet pills). The 1988 National Adolescent Student Health Survey indicated that 8% of female students reported vomiting and 11% of female students reported use of diet pills or diet candies either some of the time or most of the time when dieting [9].

Although being overweight was more prevalent among black women, the proportion of adult women who considered themselves to be overweight did not differ by race. Among high school students of both sexes in the Youth Risk Behavioral Survey, blacks were less likely than whites or Hispanics to perceive themselves as overweight. Black-white differences in weight perception were also observed in the 1985 Health Interview Survey [12] and in a study of adolescents attending two inner-city schools [13]. These findings suggest that greater body weight may not carry the same negative connotations among blacks as among whites [13].

The limitations of both surveys must be considered when interpreting these findings. The sampling frame for the Youth Risk Behavioral Survey included only those adolescents attending school, whereas the Behavioral Risk Factor Surveillance System included only those adults residing in households with telephones. All information in both surveys was self-reported; however, the Youth Risk Behavior Survey did not include information about current weight and height. Finally, because intentional vomiting and diet pill use may be considered secretive behaviors, the prevalence of these practices was probably underestimated.

Further investigation is needed to document the ways in which weight-loss practices change from adolescence to adulthood and to identify effective ways to encourage appropriate weight perception and adoption of healthy weight control behaviors in both adolescents and adults.