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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Arch Intern Med. Author manuscript; available in PMC 2009 April 22.
Published in final edited form as:
PMCID: PMC2672042

Under-diagnosis of Obesity in Adults in U.S. Outpatient Settings

Jun Ma, MD, PhD, Lan Xiao, PhD, and Randall S. Stafford, MD, PhD*

Obesity affects nearly 32% -- over 60 million – American adults.1 The obesity epidemic imposes an enormous cost on the nation’s health2 and economy3. Evidence-based clinical guidelines recommend that treatment for obesity incorporates a two-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 U.S. outpatient settings is limited.

We examined the rates of obesity screening and diagnosis in a nationally representative sample of visits by patients aged ≥18 years to private physician offices and hospital outpatient departments (OPDs) across the United States. Data were obtained from the 2005 National Ambulatory Medical Care Surveys conducted by the National Center for Health Statistics (NCHS) ( Patient, physician, and clinical information is collected at each randomly selected visit and is recorded on NCHS standard Patient Record Forms (PRFs). Measurements of height and weight were captured for the first time in 2005. Body mass index (BMI) and obesity were defined according to accepted standards.4 Physician diagnoses were documented using open-ended responses for (up to three) visit diagnoses, which were later coded by NCHS staff according to the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), and checkboxes for a pre-specified 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, NC) 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 of age and older made an estimated total of 845 million outpatient visits (95% CI: 757 million to 932 million). Measurements were recorded during 42% (95% CI: 39%–46%) of total visits for height, 65% (62%–68%) for weight, and 41% (37%–45%) for both height and weight. Of the visits for preventive care only, the corresponding rates were 52% (46%–58%), 75% (71%–80%), and 51% (46%–57%), respectively. Of the total visits in which BMI was obtainable, 37% (35%–40%) were for patients with a BMI ≥30.0 kg/m2.

Only 29% (25%–32%) of visits by patients who were obese according to their BMI had a documented diagnosis of obesity (Figure). The proportion of visits with a diagnosis of obesity was 19% (95% CI: 15%–22%) for patients whose BMI was between 30.0 and 34.9 kg/m2, 32% (26%–38%) for those whose BMI was between 35.0 and 39.9 kg/m2, and 50% (43%-57%) for those whose BMI was 40.0 kg/m2 or greater. Obesity diagnosis was noted in <2% of visits by patients whose BMI was <30.0 kg/m2. Due to the under-reporting 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 U.S.. Physicians both fail to obtain needed biophysical patient data and then fail to 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, 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 provider skills or financial incentives to address obesity, provider/patient concerns about weight stigma, and anti-fat bias by providers.6, 7 Obesity is a complex chronic condition, health care providers have an important role in preventing, identifying and managing obesity.4 BMI 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 development of innovations or modifications in care delivery to improve health outcomes for obese patients.


Funding source: This research was supported by internal funding from the Palo Alto Medical Foundation Research Institute (Ma and Xiao) and by National Institutes of Health funding (Stafford, K24 HL086703). Previous funding (R01 HS11313–01) from the Agency for Healthcare Research and Quality, Rockville, Md., supported the development and evaluation of the quality indicators used in the present study. 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.

Data access and responsibility: 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. Dr. Xiao performed and takes responsibility for the accuracy of the data analysis.


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