Judy Kruger, PhD, MS, Deborah A. Galuska, PhD, MPH, Mary K. Serdula, MD, MPH, Deborah A. Jones, PhD

Transcription

1 Attempting to Lose Weight Specific Practices Among U.S. Adults Judy Kruger, PhD, MS, Deborah A. Galuska, PhD, MPH, Mary K. Serdula, MD, MPH, Deborah A. Jones, PhD Background: Methods: Results: Conclusions: Americans spend over $33 billion annually on weight-loss products and services. Although weight-control methods are of considerable public health interest, few national data on weight-loss practices are available. This paper examines the prevalence of specific weightloss practices among U.S. adults trying to lose weight. Data from the 1998 National Health Interview Survey, which was conducted through face-to-face interviews of a nationally representative sample of U.S. adults (n 32,440), were analyzed in Twenty-four percent of men and 38% of women were trying to lose weight. Attempting weight loss was less common among normal weight (body mass index [BMI] 25 kg/m 2 ) people (6% men, 24% women) than overweight (BMI 25 to 30 kg/m 2 ) people (28%, 49%) or obese (BMI 30 kg/m 2 ) people (50%, 58%). Among those trying to lose weight, the most common strategies were eating fewer calories (58% men, 63% women); eating less fat (49%, 56%); and exercising more (54%, 52%). Less frequent strategies were skipping meals (11% men, 9% women); eating food supplements (5%, 6%); joining a weight-loss program (3%, 5%); taking diet pills (2%, 3%); taking water pills or diuretics (1%, 2%); or fasting for 24 hours (0.6%, 0.7%). Only one third of all those trying to lose weight reported eating fewer calories and exercising more. Increased efforts are needed among all those trying to lose weight to promote effective strategies for weight loss, including the use of calorie reduction and increased physical activity. (Am J Prev Med 2004;26(5): ) 2004 American Journal of Preventive Medicine Introduction The current national preoccupation with weight loss and dieting is demonstrated by the fact that Americans now spend over $33 billion annually on related products and services. 1 Despite these expenditures, Americans are getting heavier nearly 30.5% are obese. 2 Obesity is a known risk factor for numerous chronic diseases, 3 and clinical trials have shown that even modest weight loss can reduce risk factors for such diseases. 4 Current guidelines recommend that all individuals trying to lose weight use both reduced caloric intake and increased physical activity. 4 Even with the recent increase in obesity, 2 few national studies on specific weight-loss strategies have been published since the early 1990s. 5 7 A better understanding of current weight-control strategies among Americans may help From the Center for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Nutrition and Physical Activity, Atlanta, Georgia Address correspondence and reprint requests to: Judy Kruger, PhD, MS, Division of Nutrition and Physical Activity, Centers for Disease Control and Prevention, 4770 Buford Highway, NE, Mailstop K-46, Atlanta GA ezk0@cdc.gov. the promotion of more effective weight-management practices. Data from the 1998 National Health Interview Survey were used to describe the prevalence of weight-loss strategies among U.S. adults and are analyzed in The objectives of this article were to describe characteristics of people trying to lose weight and, among those who reported doing so, to describe specific weight-loss strategies and characteristics of those who used the recommended weight-loss strategies of calorie reduction and increased physical activity. Methods The National Health Interview Survey is an annual survey of non-institutionalized civilian adults in the United States. It is operated by the National Center for Health Statistics, and data are collected by the U.S. Bureau of the Census through face-to-face interviews. The National Health Interview Survey uses a stratified, multistage probability design to sample a U.S. non-institutionalized household population. The overall response rate for sampled adults was 73.9%. 8 Analyses were conducted using the adult ( 18 years) sample (n 32,440). Respondents were asked, Are you now trying to lose weight, gain weight, stay about the same, or are you not trying 402 Am J Prev Med 2004;26(5) /04/$ see front matter 2004 American Journal of Preventive Medicine Published by Elsevier Inc. doi: /j.amepre

2 to do anything about your weight? Respondents who answered that they were trying to lose weight were then asked, Are you currently doing any of these things to control your weight? and were shown a flash card with 12 specific weightcontrol strategies: nothing, joined a weight-loss program, eating fewer calories, eating special food products such as canned or powdered food supplements, exercising more, eating less fat, skipping meals, taking diet pills, taking laxatives, taking water pills or diuretics, vomiting, and fasting for 24 hours. Respondents were asked to select as many strategies as appropriate. The response items were not mutually exclusive and any possible combination of these strategies could describe respondents weight-loss practices. Two analyses were performed, the first of which was used to characterize those trying to lose weight. Among all respondents, those with missing data on demographic characteristics (n 476), on weight and height (n 1154), and on whether they were currently trying to control their weight (n 351) were excluded. Among those trying to lose weight, people with missing information on specific weight-control strategies (n 26) were excluded. The final sample consisted of 30,433 men and women. The second analysis described specific weight-control strategies among adults trying to lose weight. Thus, of the 30,433 respondents, those not trying to lose weight (n 21,014) were excluded. The final sample for the second analysis was Data on self-reported height and weight were used to calculate body mass index (BMI) as weight (kg) divided by height (m 2 ). Respondents were assigned to one of three categories normal weight (BMI 25) overweight (BMI 25 to 30) and obese (BMI 30). 4 Among adults trying to lose weight, those meeting the recommended weight-loss strategy were defined as people who used the combination of eating fewer calories and exercising more. 4 The SUDAAN (Windows version 8.0; Research Triangle Institute, Research Triangle Park NC, 2001) software program was used to accommodate the complex sampling design. Gender-specific prevalence of those trying to lose weight was calculated by the following sociodemographic characteristics: age, race/ethnicity, education, marital status, and BMI. Among those attempting to lose weight, the overall and gender-specific prevalence of the 12 specific weight-loss practices were calculated. Multiple variable logistic regression was used to examine the association between sociodemographic factors and the use of the recommended strategy of eating fewer calories and exercising more. Results The prevalence of those trying to lose weight was 24.3% for men and 37.6% for women (Table 1). In all sociodemographic categories, more women than men were attempting weight loss. Among both genders, the lowest prevalence was among people aged 65 years as compared to younger counterparts. The proportion of people trying to lose weight increased with increasing level of education. The prevalence also rose with BMI; among men the prevalence of those trying to lose weight climbed from 6% to 28% to 50%, for people in Table 1. Prevalence of attempting to lose weight among U.S. adults ( 18 years), by gender a Characteristic Men (n 13,548) Women (n 16,885) n b % c n b % c Age (years) Race/ethnicity Non-Hispanic white Non-Hispanic black Hispanic Non-Hispanic other d Education Less than high school High school Some college College graduate Marital status Married Widowed Divorced Separated Single Body mass index (kg/m 2 ) Normal ( 25) Overweight (25 to 30) Obese ( 30) Total a Source of data is National Health Interview Survey, b Unweighted sample size of those who self-reported that they wanted to lose weight. c Percentage is weighted to be nationally representative. d Includes American Indians and Alaska natives, Asians, and native Hawaiians and other Pacific islanders. the normal, overweight, and obese categories, respectively, whereas for women comparable estimates were 24%, 49%, and 58%, respectively. Among people trying to lose weight, the top three specific strategies for men and women were eating fewer calories, eating less fat, and exercising more (Table 2). Other strategies that were less common in both men and women included skipping meals, doing nothing, eating food supplements, joining a weight-loss program, taking diet pills, taking water pills or diuretics, fasting for 24 hours, taking laxatives, and vomiting. The proportion of men and women who engaged in specific weight-loss practices differed significantly for several practices, but the magnitude of the difference was small. Women were significantly (p 0.05) more likely than men to engage in several strategies, including eating fewer calories, eating less fat, joining a weight-loss program, and taking diet pills. Men were more likely than women to skip meals or do nothing. Thirty-four percent of subjects trying to lose weight reported using the recommended strategy of eating fewer calories and exercising more, and women had greater odds of using this strategy (adjusted odds ratio Am J Prev Med 2004;26(5) 403

3 Table 2. Specific weight-loss practices among adults ( 18 years) trying to lose weight, by gender a Characteristic Men (n 3250) Women (n 6169) Total (n 9419) % b n c % b n c % b Eating fewer calories ** Eating less fat ** Exercising more Skipping meals * Nothing * Eating food supplements Joined a weight-loss program ** Taking diet pills ** Taking water pills or diuretics Fasting for 24 hours d Taking laxatives d Vomiting d *Significant difference between men and women, p **Significant difference between men and women p a Source of data is National Health Interview Survey, b Percentage is weighted to be nationally representative. c Unweighted sample size of those who self-reported that they were engaging in specific weight-loss practices. d Estimates may be unstable. [OR] 1.30; 95% confidence interval [CI] ) than men (Table 3). Persons of Hispanic origin had significantly lower odds (OR 0.80; 95% CI ) of eating fewer calories and exercising more than did non-hispanic whites. Persons who used the recommended weight-loss strategy had higher levels of education. As compared to normal-weight people, people who were overweight but not obese had slightly greater odds of using the recommended strategy to lose weight (OR 1.15; 95% CI ). There was little association between using the recommended strategy and age or marital status. The three most common weight-loss strategies were examined by BMI and, compared to normal-weight respondents, obese respondents were more likely to eat fewer calories (p 0.01) and less likely to exercise more (p 0.01). There was no difference in eating less fat by weight status (data not shown). Discussion This national survey demonstrates that 31% of U.S. adults were currently trying to lose weight. Within that group, the following findings were documented: (1) the three most common weight-loss strategies were eating fewer calories, eating less fat, and exercising more; (2) one third of those attempting weight loss engaged in the recommended strategy of eating fewer calories and exercising more; and (3) although more women than men were trying to lose weight, both genders followed similar weight-control strategies. The finding that 24% of men and 38% of women were trying to lose weight in 1998 is similar to the prevalences reported in both the 1985 (23.2% of men; 41.3% of women) and the 1990 (23.3% of men and 40.1% of women) National Health Interview Surveys, which used identical questions. 5 The prevalence found in this paper is slightly lower than that in the 1996 Behavioral Risk Factor Surveillance Survey (BRFSS), a multistate telephone survey of U.S. adults, aged 18. In the BRFSS, 29% of men and 44% of women reported that they were trying to lose weight. 6 In this study, the prevalence of trying to lose weight increased with BMI. It is surprising that the prevalence of trying to lose weight has not increased, given that the prevalence of obesity among U.S. adults has increased 8.0% between and Unfortunately, it was not possible to directly compare the prevalence of trying to lose weight by weight status between the findings of this study and earlier surveys, as weight and height were not collected in the 1985 and 1990 National Health Interview Survey. Two factors associated with not trying to lose weight are lack of success at previous weight-loss attempts 9 and satisfaction with body weight. 10 Their prevalence possibly has changed over time, although we are unaware of studies that specifically examine trends in these factors. Despite the known benefits of weight loss, 3 only half of obese respondents of both genders were trying to lose weight (50% of men and 58% of women). The National Institutes of Health clinical guidelines recommend that clinicians discuss weight loss with people who are obese. 4 Consistent with clinical guidelines, clinicians should continue to counsel the obese to reduce their body weight. Respondents trying to lose weight used a variety of strategies, and this study evaluated the prevalence of 12 weight-loss strategies in a nationally representative sample. Eating fewer calories, eating less fat, and exercising more were the most common strategies and were used by approximately half of those trying to lose weight. However, only one third of adults trying to lose weight 404 American Journal of Preventive Medicine, Volume 26, Number 5

4 Table 3. The associations between those using recommended weight-loss strategies a and characteristics among adults trying to lose weight b Characteristic n c % d OR e 95% CI Gender Men Women Age (years) Race/ethnicity Non-Hispanic white Non-Hispanic black Hispanic Non-Hispanic other f Education Less than high school High school Some college College graduate Marital status Married Widowed Divorced Separated Single Body mass index (kg/m 2 ) Normal ( 25) Overweight (25 to ) Obese ( 30) Total % a The recommended weight-loss strategy includes eating fewer calories and exercising more. b Source of data is National Health Interview Survey, c Unweighted sample size of those using the recommended weightloss strategy. d Percentage is weighted to be nationally representative. e OR adjusted for gender, age, race, education, marital status, and body mass index. f Includes American Indians and Alaska natives, Asians, and native Hawaiians and other Pacific islanders. CI, confidence interval; OR, odds ratio. reported using the recommended weight-loss strategy of eating fewer calories and exercising more. The findings in this article are higher than that reported in the 1996 BRFSS, which found that 22% of men and 19% of women reported eating fewer calories and engaging in at least 150 minutes of leisure-time physical activity per week. 6 This may be, in part, because the BRFSS more strictly defined using exercise as 150 minutes of leisure-time physical activity per week, whereas our study included anyone who reported exercising more to lose weight. Other weight-loss practices were reported by 11% of respondents. Consistent with other surveys, 11,12 the prevalence of unhealthy weight-loss strategies such as fasting, taking laxatives, and vomiting was low. In contrast to these unhealthy practices, use of prescription weight-loss pills may be appropriate for some individuals as an adjunct for weight-loss therapy. 4 However, it was not possible to tell from the data whether respondents were using prescription or nonprescription diet pills. In this study, 2% of men and 3% of women reported currently taking diet pills. The 1998 estimates of diet pill consumption are higher than the 1990 National Health Interview Survey finding that showed 0.6% of adults were currently taking diet pills. 5 This observation is consistent with the growing popularity of diet supplements for weight loss and prescription diet pills since the 1990s. 13 Women were about twice as likely to be attempting to lose weight as men. This might be explained in part by the finding that more women than men were trying to lose weight at a lower BMI (6% of normal-weight men versus 24% of normal-weight women). In contrast, among those who were obese, the gender-specific differential was modest: 50% of men and 58% of women were trying to lose weight. We speculate that this gender-specific difference may be because women have a greater concern for thinness and a higher level of body dissatisfaction than men. 14 Despite the differences between men s and women s attempting to lose weight, there were only small gender-specific differences in the prevalence of specific weight-loss strategies among those trying to lose weight. Our findings should be viewed in the context of several limitations. First, the estimates of weight-loss practices are based on self-report. We are unaware of studies specifically validating individuals responses with their actual practice. It is possible that socially undesirable behaviors such as vomiting or taking laxatives were under-reported and socially desirable behaviors such as being physically active were over-reported. Second, the questionnaire provided limited detail in terms of the intensity (e.g., amount of caloric reduction or frequency of diet pill use) of weight-loss practices. The strategy of doing nothing was included in this analysis to allow for comparison with previous analyses using the same survey. However, it is not clear if respondents misunderstood the question or whether respondents realistically reported that they were trying to lose weight with minimal effort. Third, because BMI was based on self-reported weight, overweight and obesity may be underestimated. 15 Fourth, this study did not ascertain the effectiveness of the weight-loss strategies reported. Fifth, data on some popular weight-loss diets such as restricted carbohydrate intake were not collected in this survey. Finally, this analysis is based on 1998 data and may not reflect current weight-loss approaches. Attempting weight loss is a common health behavior in the United States. Although one in every three adults is trying to lose weight, not all people who would benefit from weight loss are making an attempt. Furthermore, many who are trying to lose weight are not using effective strategies. Increased efforts are needed Am J Prev Med 2004;26(5) 405

5 to promote effective weight-loss strategies among those who are obese and to promote the use of calorie reduction along with increased physical activity in those who attempt weight loss. No financial support was provided for this manuscript. References 1. Cleland R, Graybill D, Hubbard V, et al. Commercial weight loss products and programs: what consumers stand to gain and lose. Washington DC: Federal Trade Commission, Bureau of Consumer Protection, Flegal KM, Carroll MD, Ogden CL, Johnson CL. Prevalence and trends in obesity among US adults, JAMA 2002;288: U.S. Department of Health and Human Services. The Surgeon General s call to action to prevent and decrease overweight and obesity Rockville MD: U.S. Department of Health and Human Services, Public Health Service, Office of the Surgeon General, National Institutes of Health, National Heart, Lung and Blood Institute. Clinical guidelines on the identification, evaluation and treatment of overweight and obesity in adults: the evidence report. Rockville MD: U.S. Department of Health and Human Services, Public Health Service, Horm J, Anderson K. Who in America is trying to lose weight? Ann Intern Med 1993;117: Serdula MK, Mokdad AH, Williamson DF, Galuska DA, Mendlein JM, Heath GW. Prevalence of attempting weight loss and strategies for controlling weight. JAMA 1999;282: Kettel Khan L, Serdula MK, Bowman BA, Williamson DF. Use of prescription weight loss pills among US adults in Ann Intern Med 2001;134: U.S. Department of Health and Human Services National Health Interview Survey (NHIS): public use data release. Hyattsville MD: U.S. Department of Health and Human Services, Brownell KD, Rodin J. The dieting maelstrom. Am Psychol 1994;49: Anderson LA, Eyler AA, Galuska DA, Brown DR, Brownson RC. Relationship of satisfaction with body size and trying to lose weight in a national survey of overweight and obese women aged 40 and older, United States. Prev Med 2002;35: Serdula MK, Williamson DF, Anda RF, Levy A, Heaton A, Byers T. Weight control practices in adults. Am J Public Health 1994;84: Levy AS, Heaton AW. Weight control practices of US adults trying to lose weight. Ann Intern Med 1993;119: Marketdata Enterprises Inc. Diet segment bulks up. Nutr Business J 2000;5: Cachelin FM, Striegel-Moore RH, Elder KA. Realistic weight perception and body size assessment in a racially diverse community sample of dieters. Obes Res 1998;6: Rowland ML. Self-reported weight and height. Am J Clin Nutr 1990;52: American Journal of Preventive Medicine, Volume 26, Number 5