"If you use this treatment for 20 weeks, you have a positive effect on body weight," said lead researcher Dr. Tina Vilsboll, head of the Diabetes Research Division at Gentofte Hospital of the University of Copenhagen. "The hope is that we have a new class of treatment for obesity, and not just for type 2 diabetes."
"It's not a wonder drug," Vilsboll stressed. "It doesn't make everyone normal weight, but it's a way of changing your lifestyle."
And she does not recommend using these drugs as a standalone treatment for weight loss. "Not right now, we need more details," Vilsboll said.
Her team published its findings in the Jan. 10 online edition of the BMJ. The study did not receive drug company funding.
GLP-1 is a hormone naturally produced in the human gut, and GLP-1 therapy has become a new treatment for patients with type 2 diabetes because of it seems to helps regulate blood sugar.
However, doctors have also noticed that these drugs also suppress the appetite, making them intriguing candidates for treating obesity, the researchers said.
These injectable drugs were approved by the FDA in 2005, with their use limited to treating people with type 2 diabetes.
To find out more about the effect of the medications on weight loss, Vilsboll's team looked at data from 25 studies involving more than 6,000 patients. This process, called a meta-analysis, attempts to find commonalities in data between studies.
The Danish group found that patients taking GLP-1R agonists for at least 20 weeks lost more weight than those not on the drugs.
Both diabetics and people without diabetes lost weight while on the meds. In fact, weight loss was actually greater among non-diabetics, Vilsboll's group found.
According to Vilsboll, some patients lost almost 20 pounds. In her own practice, some of her diabetic patients have lost as much as 50 pounds, some of it due to the drug but even more from their newfound ability to be more active, she said.
In addition, people taking the drugs often saw improvements in blood pressure, lowered cholesterol and -- among diabetics -- better control of blood sugar levels, the researchers found.
GLP-1 agonists did have some side effects including nausea, vomiting and diarrhea. However, these side effects didn't seem to affect the number of people who dropped out of the trials, the researchers noted.
The authors conclude that their study "provides convincing evidence that GLP-1R agonists, when given to obese patients with or without diabetes, result in clinically relevant beneficial effects on body weight. Additional beneficial effects on blood pressure and total cholesterol might also be achieved."
Still, one expert remained cautious about the potential use of these medicines in overweight non-diabetic people.
Dr. Raj Padwal, an associate professor of medicine at the Walter C. Mackenzie Health Sciences Centre at the University of Alberta in Edmonton, Canada, and author of an accompanying journal editorial, said that "these agents are currently being used to treat diabetes and they effectively improve sugar control."
In this meta-analysis these drugs seemed to reduce weight by a small amount, he said. "Perhaps the weight reductions will be greater for non-diabetics, but this remains to be proved. Until these studies are done, we don't have enough compelling evidence for these drugs in terms of their weight-reducing properties and so they should not be used 'off-label' to treat non-diabetics," Padwal said.
There also needs to be long-term data on the safety of these drugs, he added. "The data available to-date suggest that they are safe, but we need to have longer follow-up periods and greater numbers of patients," Padwal said.
Another expert, Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine, noted that "high levels of insulin, and insulin resistance [a factor in diabetes], are implicated in weight control difficulties."
In fact, insulin resistance makes weight gain easy and weight loss harder, Katz said, so it stands to reason that drugs mimicking the action of glucagons (the hormone that opposes insulin) would also facilitate weight loss.
There's also the drugs' cost and method of delivery to consider, Katz said.
According to Alice Izzo, spokeswoman forAmylin Pharmaceuticals Inc., the maker of Byetta, the cost of the drug to distributors is $291 for a 60-dose syringe, which is a 30-day supply.
But, since the drug is covered by insurance most consumers pay less, Izzo added.
"Over 80 percent of managed care patients have access to Byetta with a co-pay, which means, on average, they would pay a $25 to $35 co-pay per month," she said.
Relying on a magic pill to shrink waistlines is never the key, however. "Are GLP-1 agonists of some use in combating the epidemics of obesity and diabetes? Certainly," Katz said. "Are they alternatives to what can and should be done with feet and forks? Not by a long shot."