ObjectiveThe current guidelines recommend weight loss for patients with overweight or obesity and knee or hip osteoarthritis (OA); however, there is a paucity of data on the relation of weight loss to death among patients with OA. We aimed to examine the relation of the rate of weight loss induced by antiobesity medications over one year to all‐cause mortality among patients with overweight or obesity and knee or hip OA.MethodsUsing the IQVIA Medical Research Database, we identified people with overweight or obesity and knee or hip OA. We emulated analyses of a hypothetical target trial to assess the effect of slow‐to‐moderate (2%–10%) or fast (≥10%) weight loss induced by the initiation of antiobesity medications within one year on all‐cause mortality and secondary outcomes over five years’ follow‐up.ResultsAmong 6,524 participants, the five‐year all‐cause mortality rates were 5.3%, 4.0%, and 5.4% for weight gain or stable, slow‐to‐moderate weight loss, and fast weight loss arms, respectively. Compared with the weight gain or stable arm, hazard ratios of all‐cause mortality were 0.72 (95% confidence interval [CI] 0.56–0.92) for the slow‐to‐moderate weight loss arm and 0.99 (95% CI 0.67–1.44) for the fast weight loss arm. We found dose–response protective effects of weight loss on incident hypertension, type 2 diabetes, and venous thromboembolism but a slightly higher risk of cardiovascular disease, albeit not statistically significant, in the fast rate of weight loss arm than in the weight gain or stable arm and no significant relations of weight loss to the risk of cancer.ConclusionIn this population‐based study, a slow‐to‐moderate, but not fast, rate of weight loss induced by antiobesity medications is associated with a lower risk of all‐cause mortality in people with overweight or obesity and knee or hip OA.image