<p>Body Mass Index (BMI; kg/m²) is a widely used anthropometric indicator of obesity in epidemiologic and public health research. Recent clinical guidelines no longer support the use of BMI as a diagnostic measure of obesity, recommending instead that it be reserved for screening, surveillance, and research purposes. In this Commentary, we describe key challenges related to the use of BMI in public health research and highlight the use of BMI-for-age percentiles for older adults as an approach to address these challenges. We argue that BMI can, and should, continue to be considered as a measure of obesity status in public health research on older adults using sex-stratified BMI-for-age percentiles. We demonstrate this concept by providing evidence from an analysis examining the association between obesity and cardiometabolic risk among adults in Canada using data from the Canadian Longitudinal Study on Aging (CLSA).</p>