Introduction Nutrition education and counseling are critical to patient health. Primary care physicians are positioned to provide this counseling; however, due to a lack of nutrition education, many physicians-in-training lack these skills. This study evaluates the knowledge and self-efficacy of Keck School of Medicine (KSOM) of University of Southern California (USC) Primary Care Program (PCP) medical students after leading community-based nutrition classes. Methods First-year PCP KSOM students completed a survey immediately after teaching nutrition classes (Phase I: Spring 2017-Spring 2020) and 1-4 years after teaching (Phase II: August 2021). Open-ended responses were coded thematically, and descriptive data were analyzed in Qualtrics. Results There were 93 phase I respondents; however, not everyone answered every question. Among 45 question respondents, students reported learning about macronutrients (29%), portion sizes (16%), glycemic index (15%), and metabolic syndrome (12%). Among 57 question respondents, 49% reported having knowledge to now counsel patients about nutrition. There were 60 phase II respondents. Students reported sustained, increased nutrition knowledge (88%) and confidence (85%) from baseline, and making healthy personal dietary changes. Discussion It is important for physicians-in-training to gain nutrition education early in their career. This training can benefit student knowledge, behavior change, confidence, and their future patients through counseling.