Small study finds 18 percent weight loss with tirzepatide after bariatric surgery

Adults who regained weight after bariatric surgery or an endoscopic weight-loss procedure lost an average of 18.1 percent of their body weight after 24 weeks of tirzepatide, according to a small prospective study published June 5, 2026, in the journal Obesity Surgery ^[1].

The study followed 34 patients — 26 women and 8 men — treated at a single tertiary referral center between November 2024 and July 2025 with once-weekly subcutaneous tirzepatide at doses of 2.5 to 10 milligrams per week ^[1]. Thirty-two of them had earlier bariatric surgery and two had endoscopic bariatric therapy ^[1]. Mean total body weight loss was 18.1 percent, with a standard deviation of 5.6 percent (p < 0.0001), and waist circumference fell significantly (p < 0.0001) ^[1]. Most participants moved into a lower BMI category, with the majority reaching overweight or normal weight ^[1].

Reported side effects were limited to gastrointestinal symptoms — constipation, diarrhea and nausea — which the authors describe as generally mild ^[1]. No patient stopped treatment because of them ^[1].

The researchers defined recurrent weight gain as regaining at least 15 percent of the weight lost after a procedure ^[1]. It is a common problem: work cited in the paper reports that 20 to 25 percent of patients regain significant weight within two to five years after surgery, and roughly 25 percent regain weight within the first 24 months after endoscopic sleeve gastroplasty ^[1]. Current options include intensive lifestyle changes, nutritional counseling, psychological support, weight-management medications and a second operation ^[1]. The authors note that GLP-1 receptor agonists such as liraglutide have shown moderate effectiveness in this group, adding 5 to 10 percent weight loss ^[1].

During the study period, 55 patients with recurrent weight gain were referred to the center, and 34 were treated with tirzepatide ^[1]. In Italy, where the study took place, anti-obesity medications are not reimbursed, and the authors write that cost was taken into account in treatment decisions ^[1].

The study is small and has no control group, so it cannot show how much of the weight loss came from the drug rather than the rest of the care patients received. Exclusion criteria included type 1 diabetes, severe organ dysfunction, NYHA class IV heart failure, pregnancy or lactation, and use of other obesity medications ^[1]. Participants were followed for 24 weeks; longer follow-up has not been reported. A separate, earlier retrospective study of 21 patients without type 2 diabetes who had insufficient weight loss or weight regain after surgery found mean total weight loss of 12.0 percent after six months on tirzepatide ^[2].

Why it matters for patients

Weight regain after bariatric surgery is common and can bring back weight-related health problems ^[1]. For people in that situation, this paper offers preliminary evidence from routine practice — not from a randomized trial — that weekly tirzepatide was associated with substantial weight loss and few reported side effects ^[1]. The authors themselves call the findings preliminary ^[1].

The study does not compare tirzepatide with semaglutide, with lifestyle programs, or with a second surgery, so it cannot say which approach works better or for whom ^[1]. It also does not report whether the weight loss held after treatment stopped, and it does not address insurance coverage for tirzepatide specifically after a bariatric procedure; neither has been reported. Tirzepatide is sold in the US as Mounjaro and Zepbound.

What happens next

The authors suggest tirzepatide could be a nonsurgical option within multidisciplinary care for patients who regain weight after bariatric procedures ^[1]. Because the data on tirzepatide in this group remain limited, a randomized trial comparing it with other treatments has not been reported, and results beyond six months are not yet known ^[1].