Objective: To compare the effectiveness of the Healthy Caregivers-Healthy Children (HC2) phase 1 (2011–2014) and 2 (2015–2018) child care center (CCC)-based obesity prevention intervention(s) on child dietary practices and body mass index percentile (PBMI) outcomes over 2 years. Phase 1 was implemented via a university-based research team, and phase 2 was delivered via a train-the-trainers approach (university-based research team trains preschool-based coaches, who in turn train CCC teachers to implement and disseminate HC2). Methods: Phase 1 and 2 were both cluster randomized controlled trials of the HC2 obesity prevention intervention. Phase 1 was composed of 1224 children in 28 CCCs (12 intervention and 16 control). Phase 2 was composed of 825 children in 24 CCCs (12 intervention and 12 control). Both phases included CCCs serving low-resource, predominantly ethnic minority families. (author abstract)