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Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

Excess weight afflicts the majority of the US adult population. Research suggests that the role of primary care physicians in reducing overweight and obesity is essential; moreover, little is known about self-care of obesity. This report assessed the secular trends in the care of overweight and investigated the secular association between obesity with care of overweight in primary care and self-care of overweight. Cross-sectional evaluation of the National Health and Nutrition Examination Survey (NHANES) III (1988–1994) and the Continuous NHANES (1999–2008) was employed; the total sample comprised 31,039 nonpregnant adults aged 20–90 years. The relationship between diagnosed overweight, and directed weight loss with time and obesity was assessed. Despite the combined secular increase in the prevalence of overweight and obesity (BMI >25.0 kg/m2) between 1994 and 2008 (56.1–69.1%), there was no secular change in the odds of being diagnosed overweight by a physician when adjusted for covariates; however, overweight and obese individuals were 40 and 42% less likely to self-diagnose as overweight, and 34 and 41% less likely to self-direct weight loss in 2008 compared to 1994, respectively. Physicians were also significantly less likely to direct weight loss for overweight and obese adults with weight-related comorbidities across time (P < 0.05). Thus, the surveillance of secular trends reveals that the likelihood of physician- and self-care of overweight decreased between 1994 and 2008 and further highlights the deficiencies in the management of excess weight.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

Population estimates from 2008 revealed that more than two thirds of the US adults were either overweight or obese (1). Such trends are alarming, as obesity is associated with well-established risk of comorbidity and mortality (2,3). Research has revealed that even modest weight loss (5–10% decrease of initial body weight) is favorable, as it is associated with improvement in blood pressure, lipid profile, and glycemic control (4,5,6); thus, the reduction of excess weight is a target for study and intervention.

Still, despite the documented benefits of weight loss for overweight and obese individuals, the prevalence of weight loss effort among overweight and obese individuals is relatively low. Data from the National Health Interview Survey indicate that fewer than half of overweight men and women and less than two thirds of obese men and women were attempting weight loss in 1998 (7). Research suggests that physician involvement in weight loss is associated with increased intention to lose weight, commencement of weight loss, and improved weight loss maintenance in overweight and obese patients (8,9,10). However, physician care of obesity is infrequent and inconsistent (11,12,13), and physicians are selective when diagnosing overweight and prescribing weight loss (11,12,13,14). Furthermore, physicians are generally unfamiliar with the thresholds for obesity and abdominal obesity that indicate increased cardiometabolic risk (15); thus, although physicians recognize that counseling on weight loss is an essential component of their clinical practice (16), overweight and obese individuals may go undiagnosed.

Some research suggests that counseling for weight management delivered by health professionals may be decreasing over time (17,18,19). However, the secular trends of physician diagnosis of overweight and obesity and physician-directed weight loss during the past 20 years, using nationally representative data and objectively measured height and weight, have yet to be examined at length. Furthermore, little is known about the concurrent secular trends of self-care of overweight and obesity among adults in the United States.

Thus, the objectives of the following analysis were to evaluate the secular trends in the care of overweight (diagnosed overweight and directed weight loss), to investigate the association between obesity and care of overweight in primary care over time, and by comorbidity status, and to examine the association between obesity and self-care of overweight over time.

Methods and Procedures

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

Survey methods

The National Health and Nutrition Examination Survey (NHANES) is a series of nationally representative surveys focusing on varying health issues, to produce national health statistics. The third NHANES (1988–1994) comprised two phases, each using a complex, multistage, probability sampling method to select a cross-sectional sample representative of the total noninstitutionalized civilian population in the United States. Starting in 1999, NHANES became a continuous survey that released data on a biannual basis.

For data obtained at the mobile examination center, medical technicians undergo extensive training prior to and during data collection; all anthropometrics were measured during the physical examination and have been collected using similar protocol since 1988 (20,21). BMI was computed as weight in kilograms divided by height in meters squared. Waist circumference was measured to the nearest 0.1 cm at the midaxillary line of the body. Standard BMI categories for normal weight, overweight, and obese, and sex-specific cutoffs for waist circumference (men: 94 and 102 cm; women: 80 and 88 cm) were utilized in the analyses. Physician- and self-diagnosis of overweight and physician- and self-directed weight loss were assessed using data collected by questionnaire; questionnaire data assessing the care of obesity were not available in NHANES; thus, the assessment of diagnosis and treatment of overweight were utilized in this analysis to represent that of excess weight as a whole. Respondents were asked if ever told by a doctor that they were overweight, if ever told by a doctor to lose weight for hypertension or hypercholesterolemia, if they considered themselves overweight, and if they had attempted weight loss during the previous 12 months. To evaluate secular trends and associations, the survey year was used to represent time. The combined sample (composed of NHANES III and NHANES continuous surveys) included 103,577 adults (total screened sample); after exclusions, the combined sample comprised 31,039 nonpregnant adults, 20–90 years of age. NHANES participants completed written informed consent, and the NHANES institutional review board/NCHS research ethics review board approved study protocol.

Statistical analyses

For the purpose of this analysis, individuals with missing data for age, sex, BMI, and those with a BMI <18.5 kg/m2 were excluded. The unadjusted, weighted secular prevalence of overweight and obesity, diagnosed overweight and directed weight loss, was assessed using the survey frequency procedure; changes over time in these measures were examined using trend analysis by logistic regression. Trend analysis using multiple logistic regression analysis was conducted to determine secular changes in the association between care of overweight with obesity and time. Separate analyses to assess the interaction between obesity and time (BMI × time; waist circumference (WC) × time) were also modeled. Where the interactions were statistically significant (P < 0.05), the models were stratified by BMI and WC categories, respectively. All analyses were performed using SAS statistical software (version 9.2) (SAS Institute, Cary, NC).

All multivariate analyses were adjusted for age, sex, ethnicity, education level, and smoking status. Analyses of physician-diagnosed overweight, physician-directed weight loss for hypertension, and physician-directed weight loss for hypercholesterolemia were further adjusted for health insurance; the analysis of physician-directed weight loss for hypertension was restricted to those taking antihypertensive medication, and the analysis of physician-directed weight loss for hypercholesterolemia was restricted to those taking lipid-lowering medication.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

Weighted sample characteristics are reported in Table 1.

Table 1.  Weighted sample characteristics, across survey years
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Secular prevalence of diagnosed overweight and directed weight loss

Nearly 70% of respondents were classified as overweight or obese in 2008, a significant increase since 1994 (Figure 1); similar increases in abdominal obesity were observed (results not presented). Though the prevalence of both reported physician- and self-diagnosed overweight increased across time, the prevalence of self-diagnosed overweight was substantially higher than physician diagnosis for each survey year (Figure 1). Significantly more respondents with hypercholesterolemia, but not hypertension, reported being directed to lose weight in 2008 than in 1994 (Figure 1). Contrarily, respondents reported directing their own weight loss less often in 2008 than in 1994 (Figure 1).

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Figure 1. Weighted secular prevalence of overweight and obesity, and care of obesity measures, among US adults between 1994 and 2008. (a) Physician-diagnosed overweight (PHYSdiagOW) and self-diagnosed overweight (SELFdiagOW); (b) physician-directed weight loss for hypertension (PHYSwlHBP), physician-directed weight loss for hypercholesterolemia (PHYSwlHBC), and self-directed weight loss (SELFwl); the weighted prevalence of PHYSwlHBP and PHYSwlHBC applies to individuals with diagnosed hypertension and diagnosed hypercholesterolemia, respectively.

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Association between diagnosed overweight and directed weight loss with time

The interaction between time (survey year) and BMI was significant for self-diagnosed overweight (P < 0.05) and self-directed weight loss (P < 0.0001), but not for physician-diagnosed overweight or physician-directed weight loss for hypertension and hypercholesterolemia (P > 0.05). Accordingly, we elected to stratify the models by BMI category (overweight, obese) to further evaluate the interaction between time and BMI.

The secular evaluation of care of obesity herein is relative to 1994 (the earliest year of measurement), with the exception of physician-diagnosed overweight, where 2000 is the earliest year of measurement. There was no main effect of time (secular effect) on physician-diagnosed overweight among overweight individuals (P = 0.093); however, physicians were less likely to diagnose obese individuals as overweight in 2002 (odds ratio (OR): 0.83 (95% confidence interval: 0.69, 0.99)) and 2004 (OR: 0.77 (95% confidence interval: 0.65, 0.92)) than in 2000, but not in 2006 (OR: 0.86 (95% confidence interval: 0.72, 1.02)) or 2008 (OR: 0.86 (95% confidence interval: 0.73, 1.01); Table 2).

Table 2.  Unweighted adjusted odds of being diagnosed overweight, over time by BMI category
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The likelihood of self-diagnosing as overweight was significantly lower in years successive to 1994. In 2008, overweight individuals were 42% less likely to self-diagnose as overweight compared to overweight individuals in 1994 (Table 2). However, the association between time and self-diagnosed overweight in obese individuals was much less consistent: obese individuals were 22, 26, and 40% less likely to self-diagnose as overweight in 2000, 2004, and 2008, respectively; but no less likely to self-diagnose as overweight in 2002 (OR: 0.88 (95% confidence interval: 0.69, 1.11)) or 2006 (OR: 0.90 (95% confidence interval: 0.72, 1.13)) than in 1994.

Overweight individuals with hypertension were significantly less likely to be directed to lose weight by their physician in 2000 (OR: 0.68 (95% confidence interval: 0.53, 0.87)) and 2002 (OR: 0.63 (95% confidence interval: 0.49, 0.81)), but not in 2004, compared to 1994 (Table 3). Similarly, obese individuals were 31–40% less likely to be told to lose weight for hypertension between 2000 and 2004, relative to 1994. Overweight individuals with hypercholesterolemia were 17–29% less likely to be told by a physician to lose weight between 2000 and 2006 relative to 1994; however, there was no difference in 2004 or 2008 (Table 3).

Table 3.  Unweighted adjusted odds of physician-directed weight loss and self-directed weight loss, over time by BMI category
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Both overweight and obese individuals were consistently less likely to direct their own weight loss over time (Table 3). Notably, overweight and obese individuals were 34 and 41% less likely, respectively, to self-direct weight loss in 2008 compared to those in the corresponding BMI category in 1994.

Results for analysis with waist circumference are not shown; however, it should be noted that they were similar to the results of analysis using BMI.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

Despite the overall secular increase in the prevalence of overweight and obesity, the likelihood of physician-diagnosed overweight went unchanged between 2000 and 2008, and both overweight and obese individuals were less likely to self-diagnose overweight across time. Similarly, overweight and obese individuals were less likely to be physician- or self-directed to lose weight across time.

Evidence suggests that the threshold for self-classification as overweight has increased during the past two decades (22,23,24). That, in this analysis, overweight respondents were 29–42% less likely to self-diagnose as overweight in years successive to 1994 may reflect the shifting threshold for self-perception of overweight across time. Evidence also reveals that self-reported ideal body weight has increased over time (25,26). As those who are satisfied with body weight are less likely to perceive a weight problem (26), it is thus plausible that the decreasing likelihood of self-diagnosed overweight over time observed in this analysis is in part a product of these trends. Furthermore, research suggests that obesity in one's social network may influence acceptance of increased weight and may encourage poor eating and exercise behavior (27). In this analysis, we demonstrated that both overweight and obese respondents were considerably less likely to self-initiate their own weight loss in 2008 relative to 1994. Given the now widespread commonality of overweight and obesity, it is possible that these factors may ultimately translate into a smaller proportion of overweight individuals interested in losing weight over time.

In this study, there was no change in the adjusted odds of physician-diagnosed overweight among overweight individuals; though, obese respondents were less likely to be physician-diagnosed as overweight in 2002 and 2004, compared to 1994—a trend that is consistent with findings reported previously (17,19). This result is alarming considering that simple and inexpensive anthropometric measures for identifying overweight and evidence-based guidelines for the assessment of overweight and obesity in the clinical setting have been endorsed in national guidelines (5). It has also been demonstrated that the tendency to misperceive BMI status affects physicians (28). Furthermore, the BMI cutoffs used to classify adults as overweight were lowered by the Centers for Disease Control and Prevention from 27.8 for men and 27.3 for women to 25.0 kg/m2 for all adults (5). Physicians who were not aware of this change may have been less likely to diagnose overweight patients as such until they reached a greater BMI. Alternatively, these results may reflect the tendency for physicians to skip making a clinical diagnosis of overweight; it is plausible that physicians may be prioritizing other issues in primary care ahead of documenting overweight as a clinical diagnosis. This possibility is even more compelling when considering that physicians often cite lack of time as a barrier to the delivery of weight management counseling in general (11,29,30,31,32).

To investigate secular trends in physician-directed weight loss, directed weight loss among those with hypertension and hypercholesterolemia was evaluated. Overweight and obese individuals with hypertension and overweight individuals with hypercholesterolemia were significantly less likely to be directed to lose weight by a physician across time. It is possible that the pessimism among physicians in primary care about the efficacy of weight loss counseling (11,12) may be contributing to these trends. Furthermore, reports indicate that the use of antihypertensive medication (33) and lipid-lowering agents (34) has increased significantly during the past two decades. The widespread popularity and selection of medications to manage obesity-related comorbidities, combined with the lack of pharmaceutical treatment options for weight management, are likely contributing to the tendency among physicians to address weight-related comorbidities with pharmaceutical options rather than with weight reduction, even though weight reduction as a treatment for hypertension and hypercholesterolemia is endorsed by national guidelines (35,36).

A growing body of evidence suggests that provider-directed weight reduction is associated with greater intentions to lose weight and commencement of weight loss among patients (8,10,17), and patients with whom the physician has greater contact are more likely to be counseled on weight loss (12,18). Though physician involvement in weight management is by no means fulfilled by diagnosing a patient as overweight or prescribing weight loss, the monitoring of these behaviors nonetheless provides an indication of how the weight management practices of US physicians are changing over time. In this analysis, we observed that physicians are no more likely to engage in weight management practices with their patients across time, despite the rise in obesity and the greater frequency of visits to primary care by obese adults compared to their normal weight counterparts (37). However, numerous barriers to weight-related counseling have been cited frequently by physicians, including lack of time (11,29), lack of reimbursement (13,29), and poor confidence, knowledge, and experience in weight-related counseling (11,13,14); these factors may, in part, explain the stagnant rates of provider-care of obesity. Additionally, though Medicare policy was revised in 2004 stipulating the removal of language inferring that obesity shall not be considered an illness (38), research indicates that little more than financing bariatric surgery for patients with comorbid conditions is available as a treatment option for obesity (39). Medicaid coverage of obesity assessment and treatment in primary care is reflective of the limited scope of the Medicare policy (39). The secular interplay of obesity-related action among physicians in primary care and cited barriers warrants further investigation.

Several limitations of this analysis exist. Although the use of multiple surveys allowed for the evaluation of trends over time, it also introduced potential inconsistencies between questionnaires because of varying survey protocols, and the unavailability of data in some surveys limited the secular evaluation of some analyses. Another inherent limitation is the use of self-reported data. Though the potential for respondents to misreport information is a possibility, alternative methods for collecting information on physician activity were not available. Moreover, there were few questions assessing care of excess weight available in NHANES; thus, we were unable to address care of overweight, obesity, and abdominal obesity, as separate entities; and, how recently physicians diagnosed overweight and directed weight loss is not known. Additionally, changing treatment option availability for obesity and obesity-related comorbidities over time introduces the possibility of inconsistency in the physician-directed weight loss variables. Furthermore, a large portion of the combined sample was excluded from analysis (missing data for age, sex, and BMI), and we were unable to weight the multivariate analyses; thus, these results cannot be generalized to the US population.

This study illuminates the lack of physician and individual diagnosis of overweight and direction of weight loss between 1994 and 2008. Surveillance of trends over time calls attention to the scarcity in the care of obesity in the United States and provides the support needed for physicians, individuals, and policy makers alike to address the deficiencies in the diagnosis and treatment of obesity in the primary care setting and elsewhere.

Acknowledgment

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES

J.L.K. and E.A.Y. designed the study and acquired the data from the National Institutes of Health (NIH). Additionally, E.A.Y. performed the statistical analysis and wrote the introduction, methods, results, and discussion sections of the manuscript. J.L.K. and A.K.M. reviewed the data and analysis, edited the text, and designed the presentation of data (tables and figures). All three authors approved the final manuscript. There was no funding source for this research.

REFERENCES

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgment
  8. Disclosure
  9. REFERENCES