Physician Advice About Being Overweight: Association With Self-Reported Weight Loss, Dietary, and Physical Activity Behaviors of US Adolescents in the National Health and Nutrition Examination Survey, 1999–2002
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2008年06月16日 23:38:23 Monday
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作者：Ashima K. Kant, PhD and Patricia Miner, MS, RD, CDE 作者单位：Department of Family, Nutrition, and Exercise Sciences, Queens College of the City University of New York, Flushing, New York
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【摘要】 OBJECTIVE. The goal was to examine the association of physician counseling about being overweight with attempted weight loss, dietary, and physical activity/inactivity behaviors of US teens.METHODS. We used data from the National Health and Nutrition Examination Surveys 1999–2000 and 2001–2002 for 16- to 19-year-old subjects with BMI for age of 85th percentile (n = 716). Regression methods were used to examine the association of physician advice about teen weight status with covariate-adjusted differences in reported weight loss, dietary, and physical activity behaviors.RESULTS. Approximately 51% of overweight teens (BMI for age of 95th percentile) but only 17% of at-risk teens (BMI for age of 85th to <95th percentile) reported that they had been informed by a doctor about being overweight. More than 60% of those told by a doctor about being overweight had attempted weight loss in the past year, relative to 41% of those who did not receive this advice. Teens informed of their overweight status reported significantly smaller amounts of all foods and beverages and lower energy intake per kilogram of body weight in the 24-hour recall, relative to the comparison group. Physical activity and inactivity behaviors were unrelated to professional counseling about overweight status.CONCLUSION. Physician counseling regarding adolescent overweight status was associated with a positive impact on attempted weight loss and moderate dietary behaviors.
【关键词】 adolescents diet National Health and Nutrition Examination Survey obesity physician advice stages of change weight loss behaviors
Increasing prevalence of adiposity in US children and adolescents is an acknowledged public health problem, because of the associated risks for physical, psychological, and social problems and adult obesity.1–3 Although prevention of weight gain is a key to this problem, it is also important that individuals with excess body weight or risk for overweight be encouraged to adopt sensible strategies for weight management. Accordingly, the American Academy of Pediatrics has advocated discussion of weight, diet, and physical activity in routine clinical pediatric practice.4 Recent evidence suggested that >50% of overweight teens in the National Health and Nutrition Examination Survey (NHANES) 1999–2002 had been informed by a doctor or health care professional about being overweight.5 However, little is known about the impact of physician advice about body weight on weight management behaviors among adolescents. The policy statement mentioned above acknowledged a paucity of published studies that examined the effectiveness of physician weight counseling among children and adolescents. The committee based its recommendations on evidence of a higher likelihood of attempted weight loss among adults who receive advice from physicians and the efficacy of physician counseling regarding breastfeeding, smoking cessation, and physical activity in promoting desired behaviors.4 In an attempt to fill this evidence gap, we examined the association of professional counseling about being overweight with self-reported attempts to lose weight and with dietary, physical activity, and inactivity behaviors of US adolescents. METHODS Study Design We used data from the NHANES 1999–2000 and 2001–2002, conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention.6 The NHANES 1999–2002 are continuous annual surveys and the data released include 2 years at a time. The NHANES sample is a stratified, multistage national probability sample selected from 50 states of the United States. From 1999 to 2002, the NHANES oversampled a number of population subgroups, including subjects 12 to 19 years of age. The survey procedures consisted of a household interview of the sample subject, conducted by a trained interviewer, and a health examination in the mobile examination center. The mobile examination center session included anthropometric measurements, with standardized procedures. For the present study, we combined the 1999–2000 and 2001–2002 releases, as recommended by the National Center for Health Statistics.6 History of Weight Loss We determined whether teens were told by a doctor about being overweight from their responses to the following question, asked during the household interview: "Has a doctor or health professional told you that you were overweight" The information on self-perception of body weight, weight loss history, and methods used to lose weight was self-reported by 16- to 19-year-old subjects in the household interview. Dietary, Physical Activity, and Inactivity Behaviors The NHANES 1999–2002 collected dietary information by using a 24-hour recall administered by a trained dietary interviewer in the mobile examination center.6 The dietary recalls collected for the 1999 to 2001 survey years used a computer-assisted dietary interview, which included a 4-step, multiple-pass approach.6 In the NHANES 2002, the dietary data were collected by using a multiple-pass approach with dietary recall methods that are part of the integrated US Department of Agriculture and NHANES "What We Eat in America" protocol.6 The public domain dietary data provide estimates of energy, macronutrients, and micronutrients for each 24-hour recall. We merged the NHANES data with "pyramid servings" data available from the US Department of Agriculture to compute a number of other variables of interest (eg, intake of discretionary fat and added sugar).7 The household interview included queries on duration, frequency, and intensity of leisure-time physical activity in the past 30 days. The intensity classification (moderate or vigorous) was included in the public domain file. For each respondent, we determined whether any vigorous or moderate activity lasting 10 minutes was reported for the past 30 days. Questions were also asked regarding daily hours spent on television viewing and computer usage. Finally, the diet, behavior, and nutrition questions in the household interview queried about the type of milk usually consumed and the weekly frequency of eating meals in a restaurant. Analytic Sample All 16- to 19-year-old, nonpregnant/nonlactating respondents with a BMI for age of 85th percentile (according to gender-specific, 2000 Centers for Disease Control and Prevention growth charts) and with information on whether a doctor had told the respondent about being overweight were included in the analytic sample (n = 716).8 We chose BMI for age of 85th percentile (which includes teens considered at risk of being overweight and/or overweight) because our preliminary review revealed that many respondents told by a physician about being overweight were not overweight according to the criterion of BMI for age of 95th percentile. Finally, we restricted our analysis to the 16- to 19-year-old group because this group self-reported information about physician advice and weight history. For respondents 2 to 15 years of age, parents provided information about physician advice, and weight history information was not obtained. Analytic Methods We used linear or logistic regression methods to examine differences in weight loss, dietary, and physical activity behaviors reported by teens who said they were told by a doctor about being overweight, compared with those who were not. These models were adjusted for a number of covariates, including age (in years), race/ethnicity (Mexican American, non-Hispanic white, non-Hispanic black, or all other race/ethnicities), family poverty income ratio, and BMI-for-age percentile. The estimates presented in Tables 2 and 3 are adjusted means, proportions, or odds ratios obtained from fully adjusted regression models.9 All statistical analyses included sample weights and were adjusted for the complex sampling design of the NHANES by using SUDAAN 9.0.10 RESULTS Our study population included 52% overweight (BMI for age of 95th percentile) and 48% at-risk (BMI for age of 85th to <95th percentile) teens. Approximately 51% of overweight teens but only 17% of at-risk teens reported that a doctor or a health care professional had told them about being overweight. Table 1 shows the sociodemographic characteristics of teens in the analytic sample, according to whether a doctor had told them about being overweight. Of all who reported being informed by a doctor about being overweight, 76% were overweight and 23% were at risk. The gender, income, and race/ethnicity distributions of those who had been told about being overweight did not differ from the distributions of those who had not been told (P > .05, 2 test of independence). In multivariate adjusted logistic regression models, age, gender, ethnicity, and family income were not independent predictors of reported doctor advice about being overweight (P > .05); however, BMI (or BMI-for-age percentile) was a significant predictor (P < .0001). In these regression models, there was no interaction of ethnicity with poverty income ratio for predicting reported doctor advice (P .05) (data not shown). Respondents who had been told about being overweight were more likely to consider themselves overweight (84% vs 65%; P = .01) and wanted to weigh less (90% vs 70%; P = .002) (Table 2). Nearly 63% of those told by a doctor about being overweight had attempted weight loss in the past year, compared with 42% of those who did not receive this advice (P < .001); they were also more likely to have tried to avoid weight gain over the past year (Table 2). Teens who had been informed of their overweight status reported significantly smaller amounts of all foods and beverages (P = .03) and lower energy intake per kilogram of body weight in the 24-hour recall, relative to the comparison group (P < .001) (Table 3). Those teens were also more likely to report consuming 1% fat or skim milk (P = .02). Reported physical activity and inactivity behaviors of teens counseled about their weight status were not different from those of the comparison group (P > .05). BMI-for-age percentile was a significant, independent, positive predictor of respondents considering themselves overweight (P = .02) and an inverse predictor of reports of any vigorous physical activity (P = .006) in multivariate regression models that included age, gender, ethnicity, poverty income ratio, and physician advice about overweight status as covariates. There was no independent association (P > .05) of BMI-for-age percentile with all other outcomes examined in Tables 2 and 3. Finally, the interaction of BMI-for-age percentile with physician advice about weight status was not significant for any of the outcomes in Tables 2 and 3 (P > .05 for interaction). DISCUSSION The results of this study suggest a positive outcome of physician counseling about overweight status among US adolescents. The relative odds of attempted weight loss or avoiding weight gain in the year preceding the interview were more than twice as high for teens who had been informed of their weight status, relative to those who had not been informed. To our knowledge, there are no other studies in which this question was examined among adolescents. Our results, however, are in accordance with those reported for adults in the 1996 and 2000 Behavioral Risk Factor Surveillance System surveys, in which physician advice about being overweight was associated with a higher likelihood of attempted weight loss.11–13 Given the potential for encouraging weight control behaviors among teens informed of their overweight status, the percentage of at-risk and overweight teens who received such advice was low at 34%. Although the percentage increased to slightly more than 50% for overweight teens, this still leaves one half of the overweight population without the benefit of this counseling. These results differ from those of Klein et al,14 in which 76% of 14- to 18-year-old adolescents seen for well care in pediatric or family practices reported that a physician had discussed body weight during the visit. The percentage of adolescents reporting such discussions was even higher for at-risk or overweight adolescents.14 The national sample included in our study is not comparable to the group studied by Klein et al,14 in many respects. Our sample included 16- to 19-year-old subjects, with measured height and weight, and included all teens irrespective of a recent well-care encounter. However, counseling prevalence rates for teens in our study compared favorably with those reported for adults 18 years of age in the 2001 to 2003 Behavioral Risk Factor Surveillance System survey, in which 15% of overweight and 40% of obese US subjects reported receiving advice to lose weight.15 The reasons for low prevalence rates for physician counseling could not be determined in the present study but could be related to a number of physician-identified barriers, ranging from physician beliefs about lack of patient motivation and treatment futility to lack of support services for patients and limited time for counseling.16 Although informed teens were more likely to report attempted weight loss, the reporting of desirable methods for weight management, such as eating less energy, less fat, or less food, exercising, or a combination of diet and exercise, did not differ between the 2 groups. Furthermore, the differences in reporting of strategies consistent with dietary moderation (smaller amounts of foods in the 24-hour recall and use of lower-fat milk), although significant, were relatively modest. We could find no comparable published reports that examined weight management behaviors of counseled teens and their noncounseled counterparts. Bish et al13 reported that adults who received counseling about weight loss were more likely to report reduced energy intake for weight loss; however, use of exercise and diet/exercise combinations did not differ according to medical counseling status. The design of this study provides an opportunity to examine weight loss attempts and behaviors in the context of the stages-of-behavior change model of Prochaska, DiClemente, and colleagues.17,18 The proposed stages for behavior change include precontemplation, contemplation, preparation, action, and maintenance. Our results suggest that teens informed about being overweight were more likely to have moved beyond the precontemplation stage of change, in which the patient is unaware of a problem. Instead, informed adolescents were more likely to consider themselves overweight, wanted to weigh less, and tried not to gain weight, which may indicate the contemplation stage of change, showing awareness of their overweight as a problem. Most importantly, informed adolescents reported trying to lose weight in the past year, possibly indicating the action stage of change. Higher prevalence rates of moderate dietary behaviors (low-fat milk, smaller quantities, and lower energy intake) among informed adolescents are also consistent with the action/maintenance stage of change. Logue et al19 reported the duration of time spent in the action and maintenance stages to be a predictor of weight loss among adults. Because teens who reported that they received advice about their overweight status were more likely to be overweight, we adjusted all of our analyses for BMI-for-age percentile. BMI is known to be associated with energy underreporting among children and adolescents.20 We also adjusted for other potential correlates of dietary intake (gender, age, family income, and ethnicity) in our analyses. Although BMI-for-age percentile was not an independent predictor of most outcomes examined in our study, we acknowledge the possibility that overweight adolescents may be more likely to report attempted weight loss and associated behaviors because of the perceived social desirability of such responses. Therefore, we cannot rule out the possibility that differential reporting errors and residual confounding attributable to unknown or poorly measured confounders may account for some of our results. It is important to note that the survey question merely queried about whether the respondents had been told by a physician or health care professional about their overweight status. Whether such information was accompanied by a discussion of healthy food selections, the need to limit physical inactivity, and the need to increase physical activity to manage and to control weight, by either the physician or other providers such as nutritionists, cannot be determined from the available survey data. Long-term outcomes of such counseling in the persistence of weight management efforts and successful weight control among adolescents are not known and cannot be assessed from the available data. Studies designed to address these specific issues are needed to provide the answers. The results of this study suggest that physician counseling regarding adolescent overweight status was associated with positive effects on attempted weight loss and moderate dietary behaviors.【参考文献】
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