The answer may depend on which doctor you see.
"I'll probably take a wait-and-see attitude myself," said Greg Anderson, an assistant professor of family medicine at the Mayo Clinic. "The track record has not been particularly good for diet medications."
By contrast, Dr. Albert Levy, assistant professor of medicine at the Mount Sinai School of Medicine, said he has already been prescribing the same combination of drugs in the newest offering off-label for two years, a decision based on data from previous clinical trials. He said almost all of his patients lost weight when they were given the medications.
"Once the patient has learned how to control the appetite and has lost a good amount of weight, she or he is stimulated to continue to lose weight without the medications," Levy said.
The two medications in question are Belviq and Qsymia. Belviq, which contains a new medication called lorcaserin, was approved June 27. Qsymia, approved earlier this week, is a combination of two medications which had already been on the market, phentermine and topiramate.
In trials, patients taking Belviq lost about 5 percent of their total weight, while studies showed those on Qsymia lost about 10 percent of their weight. Dramatic, they are not. Still, many are hopeful that these medications will help millions of Americans deal with obesity and related conditions like heart disease, hypertension and diabetes.
Investors are banking on these drugs too. The U.S. weight loss market is estimated to be worth more than $60 billion per year. Stocks for manufacturers of both drugs jumped at the news of the drugs' approval. Analysts predict that Belviq and Qsymia sales can reach $1 billion annually.
But that's only if doctors prescribe them. Ultimately, primary care physicians will be the gatekeepers who determine the fate of these medications. Will they turn to a simpler remedy for obesity than urging their patients to eat right and exercise? Or will they view these medications as more trouble than they're worth?
"I will predict that neither will be on the market in five years," said Dr. Lee Green, professor and chair of family medicine at the University of Alberta. "They really just don't do that much.
"'Up to 10 percent weight loss' sounds great, until you look closely. That's when used by selected volunteer patients in carefully designed, closely monitored clinical trials. We'll be lucky to get half that in the real world."
Levy, meanwhile, said he would likely use Qsymia. He said he had previously been using the component medications of the new drug for only a month at a time. Given the FDA's approval for longer use, though, he said he would now consider the medication for extended periods. He said he was less comfortable with Belviq and might consider using it after it had been out longer.
Dr. Heather Agee, a general internist and office medical director at Johns Hopkins Bayview, said that she used to prescribe phentermine regularly for weight loss; "It was very effective as an appetite suppressant," she said. Yet, she said she stopped prescribing it because "I found that people didn't make the lifestyle changes and gained the weight back."
Diet Drugs of Years Past Had Considerable Side Effects
Plus, Agee said, some of her patients experienced side effects from phentermine, like palpitations and difficulty sleeping. She said she probably would not be prescribing Qsymia until it had been out long enough to ensure that it was effective and safe.
As for Anderson, he said the last diet medication he prescribed was Meridia, which was taken off the market in 2010 due to concerns over possible heart-related risks. Xenical, an FDA-approved weight loss medication still on the market today, works by stopping fat absorption -- but also causes diarrhea. Anderson said he abandoned it years ago.
"It is interesting and good that there are a couple new drugs available for weight loss," Anderson said. But he added that before prescribing either new medication, he said he'd like to see how effective they are and what the side effects will be.
For now, at least, primary care physicians will have time to make up their minds about these diet drugs. Neither Belviq nor Qsymia is currently available on the market.
Arena, which makes Belviq, cannot make the drug available until the Drug Enforcement Administration determines if it will be a scheduled substance. While Qsymia contains two medications that are already FDA-approved, it will need to be closely monitored by the Risk Evaluation and Mitigation Strategy required by the FDA.
Physicians will need to write the prescription on a specific form and fax or mail to pharmacies that have gone through a certification process to distribute Qsymia. Additionally, it is unclear what each medication will cost and how many insurers will cover their use.
While the future for the new potential blockbusters is uncertain, one thing is for sure -- the old advice to watch your diet and exercise remains the best way to lose weight and maximize health. It is worth noting that every patient in trials who lost weight on Belviq and Qsymia was also on an exercise and diet program.
"I understand the desire for a miracle pill, a silver bullet, to deal with the very difficult and stubborn problem of obesity -- but I don't think it's going to be that easy." Green said.
Anderson concurred. "It's still going to come down to exercise and diet as the best way to lose weight."