Tirzepatide produced 12.8% to 14.7% weight loss at 72 weeks in adults with type 2 diabetes

Adults with type 2 diabetes and a body-mass index of 27 or higher who took weekly tirzepatide injections lost an estimated 12.8% to 14.7% of their body weight over 72 weeks, compared with 3.2% for those who took a placebo, in the phase 3 SURMOUNT-2 trial ^[1].

Researchers screened 1,514 adults across seven countries between March 29, 2021, and April 10, 2023, and randomly assigned 938 of them to one of three groups: tirzepatide 10 mg (312 people), tirzepatide 15 mg (311 people) or placebo (315 people). All treatments were given as once-weekly injections for 72 weeks ^[1]. To join, participants had to be 18 or older, have type 2 diabetes with an HbA1c between 7% and 10% (53 to 86 mmol/mol), and have a BMI of 27 kg/m2 or higher ^[1].

At the start, the group's average body weight was 100.7 kg (about 222 pounds), average BMI was 36.1, and average HbA1c was 8.02% ^[1]. By week 72, the estimated average change in body weight was -12.8% with tirzepatide 10 mg and -14.7% with tirzepatide 15 mg, versus -3.2% with placebo. The differences from placebo were -9.6 percentage points for the 10 mg dose (95% CI -11.1 to -8.1) and -11.6 percentage points for 15 mg (95% CI -13.0 to -10.1). Both were statistically significant (p<0.0001) ^[1].

Weight loss of 5% or more was reached by 79% to 83% of people on tirzepatide, compared with 32% on placebo ^[1]. The most common side effects in the tirzepatide groups were gastrointestinal, including nausea, diarrhea and vomiting, and were mostly mild to moderate. Fewer than 5% of participants stopped treatment because of an adverse event. Serious adverse events were reported by 68 people, or 7% overall, and two deaths occurred in the 10 mg group; the investigators did not consider the deaths to be related to the study treatment ^[1].

The trial did not compare tirzepatide with semaglutide or with any other weight-management drug, so the published results do not show how the two compare ^[1]. It also enrolled only people with type 2 diabetes and a BMI of 27 or higher, so its numbers do not describe results in adults without diabetes ^[1]. The trial was funded by Eli Lilly and Company, which makes tirzepatide; several authors reported consulting fees, research funding, speaking fees or employment ties to Lilly and other drugmakers ^[1].

Why it matters for patients

Type 2 diabetes is common among people who use GLP-1 and related medications for weight, and this trial gives that group a specific set of numbers. The authors describe the weight reduction as "substantial and clinically meaningful," and the safety profile as similar to other incretin-based therapies for weight management ^[1].

Two design points matter. First, the eligibility cutoff was a BMI of 27, not 30, so the study included people in the overweight range as well as the obesity range, as long as they had type 2 diabetes and an HbA1c between 7% and 10% ^[1]. Second, the placebo group also lost weight, an average of 3.2%, which is the comparison the drug's effect is measured against ^[1].

On safety, the report gives group-level rates rather than individual risk: about 7% of all participants had a serious adverse event, and two deaths occurred in the 10 mg group that investigators judged unrelated to treatment ^[1]. The report does not break down side effects by age, other health conditions or other diabetes medications ^[1].

What happens next

The published results cover 72 weeks of treatment ^[1]. What happened to participants after the injections stopped, and whether any weight loss was maintained longer term, has not been reported in these results ^[1]. The trial is registered with ClinicalTrials.gov as NCT04657003 ^[1][2].