STEP 4 compared continuing injected semaglutide with switching to placebo after 20 weeks. It did not select people whose weight had stalled. A separate chart review described weight changes after a switch to tirzepatide, but it did not compare switching with staying on semaglutide.
Correction, November 13, 2026. The earlier version described STEP 4 as enrolling people at a weight plateau and said the switching data favored tirzepatide over continuing semaglutide. The studies did not make those comparisons. This update describes who was studied and what each group received.
What the trial compared
The STEP 4 trial started with 902 adults with overweight or obesity and without diabetes. After a 20-week run-in, 803 who reached the maintenance dose of subcutaneous semaglutide were randomized two to one to continue the drug or switch to placebo. Both groups received lifestyle intervention. Participants were not required to have reached a weight plateau. [1]
Over the next 48 weeks, average weight changed by minus 7.9% with continued semaglutide and plus 6.9% with placebo, measured from week 20. The difference was 14.8 percentage points. The authors described the average curve in the continued-treatment group as leveling off much later, around weeks 60 to 68. Neither observation establishes how an individual plateau will resolve. [1]
What happened among people who switched
A 2026 retrospective chart review followed adults treated with tirzepatide. Among the people who had switched from semaglutide, 28 who switched after an initial loss followed by weight stabilization lost an average of 8.1% of body weight over six months. The 33 who switched after limited initial response lost an average of 2.9%. The author abstract reports these groups separately. [2]
Both groups switched drugs. Their prior responses already differed, and the study had no comparison group that continued semaglutide. The results describe what happened in these charts. They do not establish that switching produces greater weight loss than continuing after a plateau.
What a weight stall can tell you about a product
The FDA explains that compounded drugs do not undergo its premarket review for safety, effectiveness and quality. It also identifies some semaglutide salt forms as different active ingredients from the form used in approved drugs. That distinction does not establish what was in any individual vial. The weight trend alone cannot identify the formulation, its strength or the cause of a stall.
What study would answer the switching question?
A direct comparison would enroll people using a defined product who had reached a prespecified plateau, then compare continuing with switching over the same follow-up. STEP 4 and the chart review answer different questions. They do not provide that comparison.
This article is for research and informational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified clinician for individual medical decisions.
