The drugs Byetta and Victoza mimic gut hormones that decrease appetite.
The review reveals that the drugs helped overweight people without diabetes shed an average of 7 pounds and those with diabetes lose an average of 6 pounds when injected daily or weekly for at least five months.
That makes these agents promising treatments for obesity, study authors say.
“It’s not a cure, but it’s a good treatment. And you still need to combine it with lifestyle changes,” says researcher Tina Vilsboll, MD, DMSc, an endocrinologist and associate professor at Gentofte Hospital in Hellerup, Denmark.
“They use it as a tool for changing their lifestyle,” she says.
Weighing Risks and Benefits
But the drugs, known as glucagon-like peptide-1 (GLP-1) receptor agonists, also come with side effects. They work, in part, by slowing the movement of food through the stomach. That can sometimes cause a good deal of nausea or even vomiting, especially after a large meal.
But Vilsboll says that side effect generally fades over time and doesn’t usually cause people to stop taking the medication.
Experts who were not involved in the review say they are cautiously optimistic about the drugs’ prospects for weight loss.
“We do have an obesity epidemic. Weight loss by traditional means -- diet and exercise -- is extremely hard, and for people who are successful initially, it’s also very hard to maintain,” says Susan Spratt, MD, an endocrinologist and the director of diabetes services at Duke University Health System in Durham, N.C.
“If we could use these drugs just in people with obesity and know that it’s safe, I think it would be a fantastic addition to our ability to treat obesity,” Spratt says.
“I’ve had [diabetic] patients lose 60 pounds with these medications. Now, those folks were 400 pounds, so they lost 10% to 15% of their body weight,” she says. “Somebody who’s 200 pounds isn’t going to lose that much.”
Drugs Can Be Used Already, but Should They?
Because the drugs are already on the market, doctors have the ability to prescribe them solely for weight loss.
But experts say such “off-label” use of the drugs can be risky.
“Off-label use happens quite a bit, actually, for obesity drugs because people are so desperate to try something,” says Raj Padwal, MD, an associate professor of internal medicine at the Walter C. Mackenzie Health Sciences Centre in Edmonton, Alberta, Canada.
Large studies testing the drugs for weight loss in people without diabetes are ongoing.
Until the results of those studies are known, “I think the off-label use of these agents would be premature,” Padwal tells WebMD.
He says Byetta and Victoza are already known to be associated with uncommon but potentially serious health risks.
In 2009, the FDA warned doctors about the possibility of kidney problems in patients taking Byetta.
Last June, the FDA sent a letter to doctors reminding them to keep a close eye on patients taking Victoza. In animal studies, the use of Victoza was associated with an increase of certain thyroid cancers. And in clinical trials, people taking the drug had more cases of pancreatitis than people who got other kinds of diabetes medications. “We don’t know the long-term safety, and that is a huge concern,” Spratt says.
Cost is another concern. Without insurance, Padwal says Byetta and Victoza can cost $300 to $500 for a month’s supply. “Given that cost, you kind of want to stick to the indications for the drug, which right now are sugar control in diabetes,” he says.