- Only 17 percent of the placebo group retained 80 percent of the weight they lost
- Meanwhile, 90 percent of the group taking Zepbound maintained that much weight
- READ MORE: Wegovy lowers risk of heart attacks and strokes, study suggests
A study shows that patients who stopped taking Eli Lilly's weight loss drug regained their weight.
Those taking tirzepatide, brand name Zepbound, regained more than 20 pounds per year after stopping the medication.
Zepbound is a rebrand of the pharmaceutical giant's existing type 2 diabetes drug, Mounjaro.
Only 17 percent of people in the placebo group retained 80 percent of the weight they had already lost with the drug, compared to 90 percent in the Zepbound group.
The news comes as a blow to Eli Lilly after the weight-loss injection was previously dubbed the 'King Kong' of its drug class because its rivals, Ozempic and Wegovy, act on only one hormone.
Zepbound is given by injection once a week and the dosage must be increased over four to 20 weeks to reach the target dosage of 5 milligrams (mg), 10 mg, or 15 mg once a week.
Only 17 percent of people in the placebo group retained 80 percent of the weight they had already lost with the drug, compared to 90 percent in the Zepbound group
It is further evidence that people must continue taking the weight loss drugs throughout their lives to maintain their effects, because people's appetites return after they stop taking them.
A British study previously found that people taking Wegovy regained two-thirds of that weight, or 12 percent of their original body weight, in the year after stopping the weekly injections.
Both Zepbound and Mounjaro contain the active ingredient tirzepatide, which works by suppressing two appetite-regulating hormones, helping people feel full for longer.
The Food and Drug Administration (FDA) has approved Zepbound for medically obese adults or people who are overweight but have at least one weight-related condition, such as heart disease.
The latest study, sponsored by Eli Lilly, followed 670 overweight and obese adults after taking the drugs for nine months.
The participants weighed an average of 237 kg at the start of the study, and lost an average of 23 kg in the first part of the study.
Half of the group then continued taking Zepbound, while the other half switched to a placebo injection.
Neither the researchers nor the participants knew which shot they were receiving.
All participants were told to try to cut 500 calories from their diet and exercise at least two and a half hours a week.
People who started on the placebo gained the weight back.
About nine in ten of those who continued to take Zepbound maintained at least 80 percent of the weight they had already lost, while only 17 percent of the placebo group were able to do the same.
Lead study author Dr. Louis Aronne, an obesity medicine specialist and professor of metabolic research at Weill Cornell Medicine in New York City, said: 'If you look at the magnitude of the weight gain, they regain about half of the weight they originally lost. over a period of one year.'
Zepbound belongs to a class of medicines called GLP-1 agonists, which mimic a hormone that helps reduce food intake and appetite by send signals to the brain that the body is full.
It also slows the stomach's ability to clear food, in part by reducing the amount of acid produced by the stomach, helping people feel full longer.
Zepbound differs from Wegovy and Ozempic in that it mimics the action of two hormones, while Wegovy only copies GLP-1.
The research was published in the journal JAMA Network.