Association Between Early Weight Loss and One-Year Weight Regain After Lifestyle-Based Obesity Treatment: A Retrospective Cohort Study

Background and Objectives: Sustained weight loss remains one of the greatest challenges in obesity management, as many individuals experience weight regain after initial treatment success. Although early weight loss has consistently been associated with greater overall weight reduction, its relationship with subsequent weight regain in routine clinical practice remains insufficiently characterized. This study examined the association between early weight loss and clinically significant weight regain among adults participating in a lifestyle-based obesity management program. Materials and Methods: We conducted a retrospective cohort study of adults receiving structured lifestyle-based obesity treatment at a tertiary care obesity clinic. Early weight loss was defined as the percentage reduction in body weight from baseline to the routinely scheduled third-month follow-up measurement. Clinically significant weight regain at one year was defined as regaining at least 50% of the maximum weight lost from baseline to nadir weight, expressed as the weight regain ratio (WRR ≥ 0.50). Logistic regression was used to examine the association between early weight loss and subsequent weight regain after adjustment for age, baseline body mass index, and baseline body weight. Sensitivity analyses included a female-only model, an alternative weight regain definition (WRR ≥ 0.25), and Firth-penalized logistic regression. Results: Among 79 participants with complete follow-up data, 9 (11.4%) experienced clinically significant weight regain at one year. Conclusions: Greater early weight loss was independently associated with lower odds of clinically significant weight regain (adjusted odds ratio 0.784, 95% confidence interval 0.646–0.950; p = 0.013). The association remained consistent in the female-only analysis and in the Firth-penalized logistic regression. When clinically significant weight regain was alternatively defined as WRR ≥ 0.25, the association remained in the same direction but did not reach statistical significance. Age, baseline body mass index, and baseline body weight were not significantly associated with the outcome.