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Categorical body mass index

Codes and Frequencies

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For sample adults and sample children ages 10-17, BMICAT reports their Body Mass Index grouped into categories: underweight (BMI less than 18.5), normal weight (BMI of greater than or equal to 18.5 and less than 25), overweight (BMI of greater than or equal to 25 and less than 30), and obese (BMI equal to 30 or more). Prior to 2020, BMICAT is only asked of adults. For 1991, 1993, 1995, and 1997-2018, IPUMS NHIS staff recoded the values of BMI to create BMICAT. Beginning in 2019, BMI was no longer made available by NCHS on the original NHIS files and BMICAT replaced BMI. For information about comparability between 2018 and earlier years, please refer to the comparability tab on BMI.


Aside from comparability challenges introduced by the 2019 redesign, there are no comparability issues. Questionnaire design changes introduced in 2019 limit comparability with earlier years. The NHIS questionnaire was substantially redesigned in 2019 to introduce a different data collection structure and new content. For more information on changes in terminology, universes, and data collection methods beginning in 2019, please see the user note.


  • 1991: Sample persons age 18+.
  • 1992: Sample persons age 18+ in quarters 1 and 2 and in 2 weeks of quarter 3.
  • 1993: Half of sample persons age 18+ in quarters 3 and 4 (excluded from AIDS supplement).
  • 1995: Half of sample persons age 18+ (excluded from AIDS supplement)
  • 1997-2018: Sample adults age 18+.
  • 2019: Sample adults age 18+.
  • 2020 2022: Sample children ages 10-17 and sample adults age 18+.
  • 2021: Sample adults age 18+.


  • 1991-1993, 1995, 1997-2022