About the BRFSS Data

Information on this page:

What do these data tell us?

  • The percent of adults (18+ years of age) in Minnesota who are overweight and obese
  • The percent of Minnesota adults who are an unhealthy weight by gender, age, education, and income
  • If a measure is increasing or decreasing

What is a weighted percent?

A weighted percent is an adjustment of the crude percent (which is just the count divided by sample size or N) and takes into account variables like sampling design and characteristics of survey respondents (e.g. age, sex, race/ethnicity) to make the percentage generalizable to all Minnesota adults. Sample weighting is done so that unbiased population estimates can be calculated using the results of a survey.

How can we use these data?

  • To inform the public about the proportion of the adult population that is overweight and obese
  • To explore trends in the percentage of overweight and obesity
  • For program planning and evaluation by state and local partners

What can these data not tell us?

  • Measures at a county level in Minnesota
  • Measures of overweight and obesity among youth under 18 years of age
  • Measures by obesity subgroup (i.e. class I, II, and III obesity)

What is the source of the data?

The Behavioral Risk Factor Surveillance System (BRFSS), administered annually by the Minnesota Center for Health Statistics in collaboration with the Centers for Disease Control and Prevention (CDC). To learn more about BRFSS, including survey methodology (i.e. how participants are chosen) and full length questionnaires, visit CDC BRFSS.

How are overweight and obese individuals identified?

For Behavioral Risk Factor Surveillance System purposes, Body Mass Index (BMI) cut points are used to classify individuals as overweight and obese. The overweight classification includes individuals with a BMI between 25.0 and 29.9. The obese classification includes individuals with a BMI of 30.0 or greater. All those with a BMI of 25.0 or greater are included in the combined category '€˜overweight or obese.'

What are the limitations of the data?

  • The Behavioral Risk Factor Surveillance System administers questionnaires to a sample of Minnesota adults in households. It does not represent all Minnesota adults, such as those in long-term care facilities, nursing homes, the military or correctional institutions.
  • BRFSS is a telephone survey and therefore does not reach adults who have no telephone. As with most surveys that rely on telephone interviewing, some subgroups, such as specific racial or ethnic minority communities, are likely to be underrepresented.
  • Overweight and obesity measures in Minnesota's adult population are based on BMI and derived from height and weight as self-reported by survey respondents. These individuals may refuse to answer specific questions or may misreport their height and weight. Individuals who have missing information for a given question due to refusal to answer or any other reason are excluded from analysis for corresponding measures.
  • BRFSS data cannot be used to derive overweight and obesity measures for youth under 18 years of age. The Office of Statewide Health Improvement Initiatives (OSHII) provides state and national obesity data on the most recent Children and Adolescent Overweight Fact Sheet.

Why can't I compare data from 2010 and before to data from 2011 and after?

Behavioral Risk Factor Surveillance System data from 2000-2010 should not be compared to data from 2011 and later. Prior to 2011, BRFSS only sampled adults in households with landline telephones. Beginning in 2011, BRFSS included adults who received the majority of their calls on cellular telephones. Also beginning in 2011, the weighting methodology changed to better account for underrepresented groups of people (such as young adults and racial/ethnic minorities) and allow for the incorporation of cellular telephone data. This new methodology reduces bias and increases the representativeness of estimates.

How was statistical significance tested?

Unless otherwise noted, differences between groups described on the Obesity pages are statistically significant. A difference, increase, or decrease is indicated as "statistically significant" when the 95% confidence intervals for weighted percentages do not overlap. In statistics, this means that two or more estimates (i.e. percentages) are significantly different at the α=0.05 significance level.

Where can I find comparison data?

CDC BRFSS measures overweight and obesity in all 50 states, the District of Columbia, Puerto Rico, the U.S. Virgin Islands, and Guam. Weight status in each state/territory can be easily tracked using the Prevalence and Trends Database.

The National Health and Nutrition Examination Survey (NHANES) provides national obesity estimates based on direct measurement of weight and height in a representative sample of the U.S. population.

What was the sample size for the survey?

Sample size (N) by year for the BRFSS data includes only respondents who answered all questions used to derive weight status category.

Survey Year N
2000 2744
2001 3811
2002 4380
2003 3760
2004 4303
2005 2749
2006 4118
2007 4654
2008 4187
2009 5511
2010 8454
2011 14387
2012 11429
2013 13450

Where can I find more technical information about the data?

To explore technical information and full datasets by BRFSS survey year, visit CDC BRFSS.