# The accuracy of self-reported height, weight and BMI in a sample of emerging adult college students across California: an observational study

## TL;DR

College students tend to overreport height and underreport weight, leading to inaccurate BMI estimates that may misclassify weight status.

## Contribution

The study identifies systematic biases in self-reported height and weight among diverse emerging adults and suggests using numerical BMI instead of categories to reduce misclassification.

## Key findings

- Participants overreported height by 1.53 cm and underreported weight by 0.77 kg on average.
- BMI was underestimated by 0.73 kg/m², with misclassification affecting 23.8% of overweight or obese participants.
- Discrepancies varied by gender, race/ethnicity, and weight but not by age or socioeconomic factors.

## Abstract

Self-reported height and weight are pragmatic, lower-cost alternatives for objective measurements but are potentially less accurate. This study examines the accuracy of self-reported measurements in a population of emerging adults.

Participants were 603 emerging adult college students aged 18 to 24 who attend public Hispanic-Serving Institutions of higher education in California, USA. The population was heterogeneous by race/ethnicity, gender, socioeconomic position, and body size. Participants self-reported height and weight; height and weight were then objectively measured during an in-person visit.

Relative to objective measurements, participants, on average, overreported their height by 1.53 cm and underreported their weight by 0.77 kg, leading to an average body mass index (BMI) underestimation of 0.73 kg/m2. The discrepancy between self-report and objective measures significantly differed by gender, race/ethnicity, and weight but not by age, sexual orientation, household poverty status, or disordered eating behaviors. Overall, 23.8% of participants with overweight or obesity would be assigned to a lower-weight BMI category based on their self-reported measurements (including 16.2% to normal weight).

In this sample of emerging adult college students, we found modest but statistically significant inaccuracies in self-reported height and weight that resulted in some misclassification of BMI-based weight status categories. Expressing self-reported BMI as a numerical value instead of categorically may be one approach to minimize bias. These results may inform bias-correction approaches in future emerging adult studies that lack the resources for in-person objective measures.

The online version contains supplementary material available at 10.1186/s12874-025-02745-5.