Evidence brief
What did the tirzepatide trials actually find?
Trials answer narrow questions in selected groups. They give averages, not a promise about one person.
Weight loss in the main obesity trial
SURMOUNT-1 was the main study of tirzepatide for weight loss. In it, adults without diabetes lost about 15% to 21% of their starting body weight on average over 72 weeks. The lower figure was for the lowest dose tested and the higher figure for the highest dose. The dummy-injection group lost about 3%.
These were averages from a maker-supported trial with regular visits and lifestyle counselling.
Compared with semaglutide
SURMOUNT-5 compared tirzepatide head to head with semaglutide, the ingredient in Ozempic and Wegovy. It was open-label, meaning everyone knew which medicine they were getting. Adults with obesity and without type 2 diabetes lost about 20% of their body weight on tirzepatide and about 14% on semaglutide over 72 weeks.
The trial was run and paid for by the maker of tirzepatide.
What happened after treatment stopped?
In SURMOUNT-4, everyone first took tirzepatide for 36 weeks. Then some were switched to a dummy injection. Over the next 52 weeks they regained weight equal to about 14% of what they weighed at the switch, while those who kept taking tirzepatide lost a little more.
The trial does not decide how long any one person remains on treatment. That belongs in a prescriber-patient decision.
Sleep apnea
Across two year-long trials in adults with obesity and moderate to severe sleep apnea, tirzepatide reduced breathing interruptions by about 25 to 29 events an hour on average. The dummy-injection groups improved by about 5 events an hour.
The result supported the Zepbound sleep-apnea approval, but it does not mean every participant was cured.
How to read a result without getting sold
A useful question for your own visit: did these studies include people like you, with your health problems and your goal?
Ready for the next piece?
Next: inspect the further reading