Comparison of phentermine, phentermine/topiramate, and liraglutide in the reduction of anthropometric parameters in patients with obesity: a real-world clinical practice study

Objective: This study aimed to compare anthropometric changes associated with phentermine, phentermine/topiramate, and liraglutide in adults with obesity. Material and methods: A longitudinal observational retrospective cohort study was conducted in 150 adults with obesity treated at a specialized endocrinology center in Lima, Peru. Patients received phentermine, phentermine/topiramate, or liraglutide as part of a structured obesity management program (n = 50 per group). Changes in body weight, body mass index (BMI), body fat percentage, and waist circumference were evaluated between baseline and six-month follow-up. Statistical analysis included non-parametric tests (Kruskal-Wallis) and pairwise comparisons using Dunn's test with Bonferroni correction. As sensitivity analyses, multiple linear regression models and analysis of covariance (ANCOVA) adjusted for potential confounding factors were performed. Results: In the overall cohort, mean weight loss was −9.1 ± 7.0 kg (−10.9 ± 6.9%). Weight loss of ≥5% was achieved by 80.7% of patients, ≥10% by 52.0%, ≥15% by 30.0%, and ≥20% by 12.0%. Weight reduction was significantly greater in the phentermine/topiramate group compared with phentermine alone (p = 0.005). No statistically significant differences were observed between the other treatment pairs for most anthropometric outcomes. Sensitivity analyses yielded results consistent with those of the primary analysis. Conclusions: In real-world clinical practice, all three pharmacological regimens were associated with clinically meaningful reductions in body weight and other anthropometric parameters. The phentermine/topiramate combination was associated with a greater magnitude of weight loss, whereas differences between treatments were limited for other anthropometric outcomes. Sensitivity analyses supported the consistency of these findings.