In a series of longitudinal analyses, we examined body mass index (BMI) of drum and bugle corps performers at the beginning (Time 1) and end (Time 2) of a competitive season and again at a 1-year follow-up (Time 3). Utilizing an archival database, BMI data were recorded for 501 marching arts performers, representing four world-class drum and bugle corps. Significant reductions in BMI were found between Time 1 and Time 2 for performers in all sections (i.e., brass, percussion, and color guard). Archival data from 92 performers, representing three world-class drum and bugle units, revealed BMI significantly increased from Time 2 to Time 3. In an effort to identify possible personal influences on the changes in BMI found between Times 2 and 3, 50 performers from one drum and bugle corps provided archival data on a measures of performers' athletic identity (i.e., the strength and exclusivity of one's identification with the athlete role) along with BMI. Correlational analyses revealed that performers' athletic identity negatively related to BMI change from Time 1 and Time 3 and Times 2 and 3 (i.e., stronger athletic identity, lower BMI change). Practical implications are discussed.