Comparing the Effect of 1000-Unit Versus 500-Unit Intragastric Botulinum Toxin A Injection for Weight Loss in Obesity: A Prospective Cohort Study

Abstract

Background: Intragastric injection of botulinum toxin type A (BTX-A) has emerged as a minimally invasive intervention for obesity management; however, the optimal dose for achieving clinically meaningful weight loss remains uncertain. Objectives: This study aimed to compare the efficacy and short-term safety of two doses of intragastric BTX-A (1000 U vs 500 U) in adults with obesity. Methods: In this prospective cohort study, 88 adults with obesity (body mass index [BMI] ≥ 30 kg/m2) underwent intragastric BTX-A injection into the gastric body using a standardized 24-point circumferential injection protocol (500 U, n = 44; 1000 U, n = 44). Participants were followed for 16 weeks, with predefined visits at baseline and weeks 1, 4, 8, and 16. The primary outcomes were changes in body weight and BMI over time. Multivariable generalized estimating equation (GEE) models were used to evaluate the association between BTX-A dose and weight outcomes after adjusting for potential confounders. Results: Both groups showed significant reductions in weight and BMI over 16 weeks (time effect, P < 0.001). At week 16, total body weight loss (TBWL) was greater in the 1000-U group than in the 500-U group (−10.21% vs −7.18%). In adjusted GEE models, 1000 U was independently associated with greater reductions in weight (β = −1.62 kg; 95% CI, −2.76 to −0.47; P = 0.006) and BMI (β = −0.53 kg/m2; 95% CI, −0.94 to −0.11; P = 0.013). Weight loss of at least 5 kg occurred more frequently in the 1000-U group than in the 500-U group (90.91% vs 61.36%; P = 0.002). Adverse events were uncommon (abdominal pain, 3.41%; nausea/vomiting, 1.14%), and no serious adverse events were observed. Conclusions: In this prospective cohort study, intragastric BTX-A at 1000 U achieved greater short-term weight loss than at 500 U, with a comparable safety profile. These findings suggest a potential dose-response effect and warrant confirmation in randomized controlled trials with longer follow-up.