What you’ll learn from the 2024-2025 studies and what they can’t prove
What did new Tirzepatide and GLP-1 studies find?
You’ll start with SURMOUNT-5 and SURMOUNT-1, the two main weight studies. You’ll learn who enrolled and what the results won’t answer.
What did the first Tirzepatide studies find?
Two large studies weighed people over time. SURMOUNT-5 ran for 72 weeks in 2025. Average weight change with tirzepatide was -20.2%. The minus sign means weight went down. The other weekly shot brought -13.7% [5]. In SURMOUNT-1, the top dose brought -20.9%. The placebo group changed by -3.1%. That study included 2,539 adults with obesity [4].
Tirzepatide is a prescription drug for type 2 diabetes. That study also lasted 72 weeks. May 2022 brought the first approval. November 2023 added approval for lasting weight care. Doctors can also use it when obesity comes with serious sleep apnea.
The drug has a 39-amino-acid chain. Proteins use amino acids as tiny building pieces. The count won’t forecast what happens to you. One copied gut hormone is called GLP-1. It can lower hunger. Tirzepatide copies GLP-1 and a second hormone.
Older drugs copied only GLP-1. Tirzepatide copies both gut hormones. That’s the main difference.
First, we’ll look at who joined the studies. Then you’ll see what changed and where proof is weak. People’s own accounts are on the Tirzepatide effects page.
These are group averages, so they can’t name your result and won’t choose your dose. They don’t know your other medicines, so you’ll need a doctor who knows you. Your doctor isn’t guessing from one number because that’s how the figures fit your care.
How does Tirzepatide work in your body?
A meal makes your gut release two hormones. One is GLP-1, which tells your pancreas to send insulin. GLP-1 can also lower hunger. Tirzepatide copies GLP-1 and the other hormone.
Copied GLP-1 can make your stomach pass food more slowly. Fullness may last longer for you. The drug also reaches brain areas that control hunger.
The first test used cells in a lab dish. Cells responding to GLP-1 stayed active longer [2]. That finding didn’t show more insulin in a person. It also didn’t measure hunger, weight, or safety.
First came the dish tests. Then studies in people found more weight loss and a larger sugar drop. The other drug copied only GLP-1 [3]. Those results came from people, not cells.
Your blood tests and how you feel will tell you more.
What changed in Tirzepatide studies from 2024-2025?
The strongest 2024-2025 finding came from SURMOUNT-5. In 2025, the adults had obesity without type 2 diabetes. Average weight change was -20.2% with tirzepatide. It was -13.7% with the other weekly shot. Each minus sign means weight fell. Tirzepatide brought the clearly larger average drop [5]. More tirzepatide users lost at least 10%, 15%, 20%, and 25% of their weight.
Another 2025 study scanned 160 people from SURMOUNT-1. The scan showed what share of the drop was fat. About 75% was fat. Muscle and other tissue made up about 25% [10]. Think of it as a scale that can sort pounds.
A third 2025 review joined 56 studies with 60,307 people. Both drugs helped people lose more than 10% versus placebo. A placebo looks like treatment but has no drug. The review found benefits for sleep apnea and serious fatty liver disease too [11]. Read more on the Tirzepatide research page.
These are group findings. Your own result still needs follow-up.
What don’t Tirzepatide studies prove?
The large phase 3 studies came late in testing, after earlier safety work. They included many thousands of adults. SURPASS-1 through SURPASS-6 studied type 2 diabetes. SURMOUNT-1, -2, -3, -4, and -5 studied obesity. Other work asked about serious liver disease caused by fat, sleep apnea, and heart failure.
Large studies give firmer group averages. They won’t settle your own result.
The studies don’t show that tirzepatide treats type 1 diabetes. Most people had type 2 diabetes or obesity. The results don’t cover people who had neither one.
Stopping matters too. In SURMOUNT-4, people moved to placebo and regained weight. People who kept taking tirzepatide lost more [14]. Constipation, diarrhea, vomiting, and nausea caused many people to quit the studies [6]. See the tirzepatide side effects page for more.
You know your diagnosis. Only a doctor who knows you can judge which group comes closest.