Underdiagnosis of Obesity in Adults in US Outpatient Settings FREE

Obesity affects nearly 32%—more than 60 million—American adults.¹ The obesity epidemic imposes an enormous cost on the nation's health² and economy.³ Evidence-based clinical guidelines recommend that treatment for obesity incorporates a 2-step process: assessment and management.⁴ Routine screening and accurate diagnosis are among the first steps leading to proper treatment. However, research on obesity screening and diagnosis in US outpatient settings is limited.

We examined the rates of obesity screening and diagnosis in a nationally representative sample of visits by patients 18 years and older to private physician offices and hospital outpatient departments across the United States. Data were obtained from the 2005 National Ambulatory Medical Care Surveys conducted by the National Center for Health Statistics (NCHS) (http://www.cdc.gov/nchs/about/major/ahcd/ahcd1.htm [accessed July 23, 2008]). Patient, physician, and clinical information is collected at each randomly selected visit and is recorded on NCHS standard patient record forms. Measurements of height and weight were captured for the first time in 2005. Body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) and obesity were defined according to accepted standards.⁴ Physician diagnoses were documented using open-ended responses for (up to 3) visit diagnoses, which were later coded by NCHS staff according to the International Classification of Diseases, Ninth Revision, Clinical Modification and check boxes for a prespecified list of current medical problems, one of which was obesity, regardless of visit diagnoses. The unit of analysis was the patient visit. National estimates were generated using the SURVEYMEANS procedure (version 9.1.3; SAS Institute, Cary, North Carolina) for the number and proportion of patient visits, including 95% confidence intervals (CIs), by taking into account the sampling weights and multistage-stratified probability sampling designs of the surveys.

In 2005, American adults 18 years and older made an estimated total of 845 million outpatient visits (95% CI, 757 million–932 million). Measurements were recorded during 42% (95% CI, 39%-46%) of total visits for height, 65% (95% CI, 62%-68%) for weight, and 41% (95% CI, 37%-45%) for both height and weight. Of the visits for preventive care only, the corresponding rates were 52% (95% CI, 46%-58%), 75% (95% CI, 71%-80%), and 51% (95% CI, 46%-57%), respectively. Of the total visits in which BMI was obtainable, 37% (95% CI, 35%-40%) were for patients with a BMI of 30.0 or greater.

Only 29% (95% CI, 25%-32%) of visits by patients who were obese according to their BMI had a documented diagnosis of obesity (Figure). The proportion of visits during which obesity was diagnosed was 19% (95% CI, 15%-22%) for patients whose BMI was between 30.0 and 34.9, 32% (95% CI, 26%-38%) for those whose BMI was between 35.0 and 39.9, and 50% (95% CI, 43%-57%) for those whose BMI was 40.0 or greater. Obesity was diagnosed in less than 2% of visits by patients whose BMI was less than 30.0. Owing to the underreporting of clinical obesity, the agreement between obesity defined by BMI and that by physician diagnosis was low (κ = 0.3).

These results indicate that obesity is underappreciated in clinical practice throughout the United States. Health care providers often fail to obtain needed biophysical patient data and do not clinically identify obesity even when data that are obtained suggest this condition. Barriers to obesity screening and diagnosis are likely multiple and may involve system, health care provider, and patient factors, including but not limited to, the lack of infrastructure to meet the needs of obese patients, lack of time for preventive care, lack of health care provider skills or financial incentives to address obesity, health care provider or patient concerns about weight stigma, and antifat bias by health care providers.^5- 6 Obesity is a complex chronic condition, and health care providers have an important role in preventing, identifying, and managing obesity.⁴ Body mass index and waist circumference are simple, validated measures of body fat that provide a reliable prediction of disease risk. Research aimed at determining the barriers to optimal health care for obese patients will guide the development of innovations or modifications in care delivery to improve health outcomes for obese patients.

Correspondence: Dr Ma, Department of Health Services Research, Palo Alto Medical Foundation Research Institute, 795 El Camino Real, Ames Bldg, Palo Alto, CA 94301 (maj@pamfri.org).

Author Contributions: Drs Ma and Xiao had full access to all of the data in the study, which is publicly available through the National Center for Health Statistics, and Dr Xiao performed and takes responsibility for the accuracy of the data analysis. Study concept and design: Ma. Acquisition of data: Xiao. Analysis and interpretation of data: Ma, Xiao, and Stafford. Drafting of the manuscript: Ma. Critical revision of the manuscript for important intellectual content: Ma and Stafford. Statistical analysis: Ma, Xiao, and Stafford. Obtained funding: Ma. Administrative, technical, and material support: Ma. Study supervision: Ma.

Financial Disclosure: None reported.

Funding/Support: This research was supported by internal funding from the Palo Alto Medical Foundation Research Institute (Drs Ma and Xiao) and by National Institutes of Health funding (Dr Stafford, grant K24 HL086703).

Role of the Sponsors: No sponsor or funding source had a role in the design or conduct of the study; collection, management, analysis, or interpretation of the data; or preparation, review, or approval of the manuscript.