About Adult Obesity Data
Tracking obesity in Iowa involves collecting data about the weight of individuals who participated in theBehavioral Risk Factor Surveillance System (BRFSS) survey. National data for overweight and obesity are provided by the Centers for Disease Control and Prevention (CDC).
This page provides general information about obesity data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.
Information on this page:
What is the source of the data?
The overweight and obesity data for Iowa are collected through the Behavioral Risk Factor Surveillance System (BRFSS). BRFSS is the nation’s premier system of telephone surveys that collect state-level data about health risk behaviors, chronic health conditions, and use of clinical preventive services among adult U.S. residents.
National data for overweight and obesity are provided by the Centers for Disease Control and Prevention (CDC).
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How does BRFSS collect data?
BRFSS invites a randomly selected sample of Iowan adults to participate in the telephone survey. Recent surveys have included both adults who have landline telephones and cell phone users, and have between 6,000 and 7,700 participants. All responses are weighted to the entire Iowan population so that weighted results are intended to capture the experience of the entire state.
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What questions were asked to collect data on overweight and obese adults?
Overweight is defined as body mass index (BMI) greater than or equal to 25.0 but less than 30.0; BMI was calculated from self-reported weight and height (weight [kg]/ height [m²]).
Obese is defined as body mass index (BMI) greater than or equal to 30.0; BMI was calculated from self-reported weight and height (weight [kg]/ height [m²]).
Respondents reporting weight of less than 50 pounds or greater than or equal to 650 pounds; height less than 3 feet or greater than or equal to 8 feet; or BMI less than 12 or greater than or equal to 100 were excluded. Pregnant respondents were also excluded.
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What time period was the data collected?
The self reporting overweight and obesity questions were asked in the BRFSS Core section every year from 2011-2017.
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Can I compare pre-2011 BRFSS data to post-2011 BRFSS data?
No. Data from 2011 and later should not be compared to data from before 2011 due to changes in data collection and analysis methodology. Earlier versions of the BRFSS survey only contacted people with landline telephones. Beginning in 2011, BRFSS changed the collection methodology to include cell phones in its sampling frame. In addition, a new method for weighting the sample called iterative proportional fitting or raking was introduced. This methodology better allows data for population subgroups that are underrepresented in the sample to be more accurately represented in weighted estimates. The raking method allows more demographic variables to be used in creating sample weights leading to more accurate estimates.
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Where can I find more technical information about the data?
To explore technical information and to review the annual reports, please visit the IDPH BRFSS website.
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