Weight Control Practices of U.S. Adults Trying to Lose Weight

Recent surveys have shown that approximately 40% of adult women and 20% of adult men report that they are currently trying to lose weight [14]. A greater percentage of adult Americans engage in weight-loss behavior over the course of a year, yet little progress has been made toward meeting national health objectives and toward reducing the prevalence of obesity in the general public [5]. This disparity raises public health questions about possible consumer protection and consumer education strategies to remedy this unsatisfactory state of affairs. The development of such strategies is handicapped, however, because little is known about what people actually do when they say that they are trying to lose weight. The 1992 Weight Loss Practices Survey (WLPS), sponsored jointly by the Food and Drug Administration (FDA) and the National Heart, Lung, and Blood Institute (NHLBI), interviewed people who were trying to lose weight and asked about more than 35 specific practices that might be used as part of a weight-loss plan (Food and Drug Administration; National Heart, Lung, and Blood Institute. Weight Loss Practices Survey, 1991. Unpublished data). The WLPS used a national probability sample of U.S. adults and dedicated the entire questionnaire to weight-loss issues. In addition to a detailed inventory of weight-loss practices, the WLPS obtained information about individual characteristics such as current weight, weight-loss history, demographic profile, motivations to lose weight, sources of information, and knowledge about diet and health. The survey was designed to estimate the relative prevalence of different types and combinations of practices among weight-loss practitioners and to describe the relations between individual characteristics and various features of weight-loss regimens. We present a broad overview of the survey results. The key classification variables used were sex, weight status defined by ranges of body mass index (BMI), and regimen characteristics. Analyses examined whether and how these variables are associated with weight-loss practices. Methods Data for the WLPS were collected in the continental United States from September to mid-November 1991. Respondents were noninstitutionalized, civilian adults, 18 years or older, who were contacted and interviewed by telephone. A two-stage sampling procedure was used to select the respondents to be interviewed [6]. The first stage involved the selection of a sample of telephone numbers through random-digit dialing procedures. In the second stage, a designated respondent was selected randomly from all adults in the household. The designated respondent was asked, Are you right now trying to lose weight? Respondents who answered yes continued the interview. Of the 10 840 households contacted, 72% completed the interview through the weight-loss screening question. Of those designated respondents who said that they were attempting to lose weight, 95% completed the WLPS interview. The total sample of 1431 persons trying to lose weight consisted of 1030 women and 401 men. Our analysis estimated the level or prevalence of weight-loss variables within each of 12 population subgroups defined by sex and three classifications of BMI (weight [kg]/height [m2]) and three classifications of regimen characteristics. Self-reported height and weight were used to calculate BMI. Respondents were assigned to one of three categories (BMI < 26, 26 to < 30, and 30). We classified persons with a BMI between 26 and 30 as overweight and those with a BMI of 30 or more as obese [7]. Because BMI was based on self-reported weights, overweight and obesity were probably underestimated. Persons consistently under-report their true weights by approximately 1 kg; however, correlations between reported weights and measured weights are typically quite high, ranging between r = 0.96 and r = 0.99 [8]. The regimen characteristics used for classification were as follows: whether respondents had combined dieting (defined as eating differently from the way you usually eat for the sake of losing weight) and exercise (as called for by most weight-loss guidelines) [7, 9]; whether respondents had been on their current weight plan for at least 1 year (an indication of a long-term commitment); and whether respondents engaged in one or more practices that might be considered questionable in some circumstances. Practices were classified as questionable based on the possibility of abuse. Questionable practices included fasting for 24 hours or longer, taking diet supplements such as high-protein or fiber supplements, using any type of diet-aid pill (for example, appetite suppressants, diuretics, or thyroid pills), vomiting after eating, taking laxatives, or using special weight-loss devices. Such practices have been associated with health problems [10] but could be considered acceptable elements of a weight-loss plan if used judiciously or while under professional supervision. For example, although it is acceptable to use diet supplements to supplement a healthy diet, it is unacceptable to use such supplements as a substitute for food to lose weight. The regimen classifications described here are not mutually exclusive and any possible combination of the three characteristics could describe an individual weight-loss plan. All survey estimates were weighted to the 1990 census distribution on sex, race, age, and education. Because of item nonresponse, the number of respondents varied slightly between analyses. Respondents were excluded only from those analyses for which they failed to answer the relevant items. Results Characteristics of Weight-Loss Practitioners The population prevalence of active weight-loss attempts was calculated by dividing the number of persons who reported attempting to lose weight by the total number of designated respondents who were contacted. Overall, 33% of women and 20% of men reported that they were currently trying to lose weight. The relative prevalence of weight-loss plans by BMI group and regimen classification variables are shown in Table 1. More than two thirds of weight-loss practitioners combined diet and exercise in their weight-loss plan, 30% had been on the current plan for 1 year or more, and 20% engaged in some kind of questionable weight-loss practice. Table 1 also shows the distribution of weight-loss plans by demographic characteristics and regimen features. Compared with the general population, persons trying to lose weight were more likely to be women, young to middle-aged, and better educated. Most men were in one of the two higher BMI categories. In contrast, about one half of women were in the lowest BMI category; that is, a substantial percentage of women who are trying to lose weight may not be overweight. Table 1. Body Mass Index Group and Regimen Features by Demographic Characteristics and Regimen Features: Percentage Distributions of Weight-Loss Practitioners* Younger persons were more likely to include both diet and exercise in their regimens but were less likely than older respondents to be on long-term regimens. More educated practitioners were more likely to be nonoverweight as determined by BMI. Weight-loss practitioners with more education were also more likely to combine diet and exercise in their weight-loss plans and were less likely to engage in questionable practices. Blacks who reported trying to lose weight were much more likely to be overweight and to engage in questionable practices than were whites. Previous Weight-Loss Experience Characteristics Respondents reported they had spent an average of 6 months of the past year trying to lose weight, had made an average of more than two weight-loss attempts during the past 2 years, and had tried their current weight-loss plan once before. Women reported more previous weight-loss attempts and more time spent trying to lose weight than did men. Tables 2 and 3 show the means for these and other survey variables by BMI groups and regimen features for women and men, respectively. Table 2. Characteristics of Current Weight-Loss Plan by Body Mass Index Group and Regimen Type for Women* Duration of Current Weight-Loss Plan The average duration of the current weight-loss attempt was between 5 and 6 months for both women and men. Duration of the current weight-loss attempt decreased dramatically as BMI level increased for both women and men. Weight-loss practitioners with higher BMI levels engaged in more frequent weight-loss attempts of shorter duration than did those with lower BMI levels, who tended to remain in a given plan for longer periods. Weight-Loss Goals Respondents reported how much weight they had lost with their current plan and how much more weight they hoped to lose. The sum of the two responses defined their weight-loss goal. Weight-loss goals were strongly related to weight status. For both women and men, as BMI levels increased, so did the amount of weight they hoped to lose. Weight-loss goals ranged from around 10 kg for those with a BMI of less than 26 to an average of almost 30 kg for those with a BMI of 30 or more. In contrast to the threefold variation in weight-loss goals, the variation in achieved weight-loss between BMI groups was modest, averaging less than 2 kg for women and less than 3 kg for men. The weight-loss goals of persons at the higher BMI levels appeared unrealistic, given the amounts of weight that they had lost so far. Information-seeking Behavior Approximately 40% of those engaged in a weight-loss attempt said that they had checked with their doctor before trying to lose weight. For both women and men, the likelihood of checking with a physician increased with BMI. Less than one third of respondents reported looking for information about how to lose weight from expert sources such as physicians, nutritionists, other health professionals, or specialized reading. Most respondents obtained information from informal sources such as friends, family members, televisi