Objective: The effectiveness of anti-obesity medications (AOMs) outside of clinical trials is unclear. The objective of this study was to compare the short-term effectiveness of AOMs in real-world practice. Methods: This retrospective study included adults aged ≥18 years, with body mass index ≥30 kg/m2 or ≥27 kg/m2 with at least one obesity-related comorbidity who were prescribed phentermine hydrochloride, phenterminetopiramate, bupropion-naltrexone, or lorcaserin for 12 consecutive weeks between 2006 and 2016 at a large tertiary healthcare system. Propensity score-matched cohorts were created for each pair of AOMs. The primary outcomes were percent and absolute weight loss from baseline after 12 weeks. A prediction model was constructed to estimate weight loss with different AOMs based on demographic and clinical data. Results: Of the 3,411 patients included in this study, patients lost an average of 3.45% of body weight from baseline. All AOMs were associated with a significant weight loss from baseline (P<.0001). Patients lost the highest percentage of body weight on phentermine hydrochloride (3.75 ± 5.66%), followed by phentermine-topiramate (3.63 ± 5.7%), bupropion-naltrexone (2.66 ± 5.03%), and lorcaserin (1.84 ± 6.69%). In propensity-matched cohorts, patients taking phentermine hydrochloride lost more weight than those taking lorcaserin or bupropion-naltrexone, and patients taking phentermine topiramate lost more weight than patients taking lorcaserin. Conclusion: In real-world practice, AOMs are associated with clinically meaningful weight loss of 2 to 4% after 12 weeks. In this study, phentermine hydrochloride and phentermine topiramate produced the most weight loss. AOMs should be seriously considered as part of the armamentarium to treat patients with obesity. Abbreviations: AOM = anti-obesity medication; BMI = body mass index; EMR = electronic medical record; FDA = Food and Drug Administration; T2D = type 2 diabetes.