GEOFF BENNETT: The number of Americans taking GLP-1 drugs for weight loss is rising sharply.

A new Gallup poll finds 11 percent of adults say they're currently using one of the medications, up from just 3 percent two years ago.

And that number could climb even higher now that Medicare has cleared the way for some patients to access these drugs, which can help reduce obesity substantially and the risk of other health problems.

Our William Brangham has the details.

WILLIAM BRANGHAM: That's right, Geoff.

Starting this month, some Medicare beneficiaries can buy these popular weight loss drugs for only $50 a month.

That is a steep discount from retail prices.

It's part of a new temporary pilot program to give millions of Americans access to the drugs that many have been unable to afford.

The program is scheduled to run through the end of 2027.

To help us fill in the picture of what people need to know, we are joined by Juliette Cubanski.

She's vice president and director of the Program on Medicare Policy at KFF.

Juliette, thank you so much for being here.

Who on Medicare will be eligible for this discounted access to these drugs?

JULIETTE CUBANSKI, Program on Medicare Policy, KFF: Millions of people are now eligible for this new program.

The program is designed to reach people on Medicare who haven't been able to access coverage of GLP-1s for weight loss specifically through their Part D plans.

That's because the law prohibits Medicare from covering drugs used for weight loss.

This temporary program is targeting people with a BMI over 35 or a BMI over 27, along with other... WILLIAM BRANGHAM: That's their body mass index.

JULIETTE CUBANSKI: Yes, body mass index.

Thank you.

So if your BMI is 25 and above, plus other conditions like prediabetes or hypertension, you might be eligible for these drugs.

But, importantly, you can't have type 2 diabetes or sleep apnea or fatty liver disease.

If you have one of those conditions, you can qualify for GLP-1 coverage now under your Part D plan.

The Bridge Program is really designed for people with obesity or overweight who don't have other conditions for which their Part D plan would cover a medication.

Our analysis shows that about four million Medicare beneficiaries meet all of the clinical and eligibility criteria for the Bridge Program.

That's a lot of people who currently are unable to access these medications under the Medicare program.

WILLIAM BRANGHAM: I want to ask you a question about costs, because, as we know, these medications are very expensive.

Now, the government's going to be shouldering some of that burden.

But, as you're describing, these -- the benefits of these medications are enormous.

So might the cost that the government is paying to pay for these drugs be offset by some of the health benefits that accrue to all of those millions of people taking the medications?

JULIETTE CUBANSKI: That's certainly the thinking and the hope, I think, over a longer term.

In the shorter term, the federal government will be subsidizing the cost of these medications over the 18-month period of this program, at a cost of about $3,500 over that 18 month period.

We're certainly not likely to see $3,500 in cost savings for the individuals who participate in this program in the short term.

The program will, I think, over a longer term produce some cost savings as people who take these medications lose weight and as their health improves.

If in the future they don't develop type 2 diabetes or their cardiovascular conditions improve, that certainly could help to generate cost savings in the future.

But we don't really know exactly whether the level of cost savings that we achieve over a longer term will equal the additional spending that the federal government will be paying for these medications in the short term.

And also over the longer term, people really need to keep taking these drugs in order to maintain the benefits.

So that will entail continuing to pay for these medications over a longer term.

Right now, that's uncertain.

But what we know is that there will be additional costs in the short term, with a hope for savings over a longer term.

WILLIAM BRANGHAM: As with all drugs, it's worth remembering that, while these drugs have huge benefits, there are also potential downsides.

One of my colleagues earlier today talked with Kathryn Porter Starr.

She's at the Duke University School of Medicine, and she had raised a couple of concerns about elderly people taking these medications.

Here's what she said.

KATHRYN PORTER STARR, Duke University School of Medicine: The concerns that we have, I think, center really around that loss of muscle mass.

Older adults already lose muscle mass with aging.

And then when we add in the GLP-1s, what we are going to possibly see is weight loss in that range of 25 to 45 percent from fat-free mass.

That excessive weight loss in our older adults may lead to that significant loss of muscle mass and bone mineral density.

And they really do recommend that we are focusing on that adequate protein intake and resistance training to mitigate that risk.

WILLIAM BRANGHAM: On top of those concerns, this program, as we mentioned, is only for one year.

So, what are the implications if someone is taking these medications for a year, but then has to stop because they suddenly have to pay full retail price for them?

JULIETTE CUBANSKI: Right.

So this program is only temporary.

The Centers for Medicare and Medicaid Services, the agency that runs the Medicare program, doesn't have the authority to change the law on its own.

That would require Congress to permanently authorize Medicare coverage of drugs used for weight loss.

So this Bridge Program, which started on July 1, is running through the end of 2027.

I mean, we certainly do know that, in order to sustain the benefits of GLP-1s for weight loss, people need to keep taking them.

You know, there are those other direct-to-consumer programs, but the $50 co-pay that beneficiaries will enjoy under the Bridge Program is considerably lower than the cost that we're seeing other patients paying through those other direct-to-consumer programs.

So, at this point, we're really not sure what will happen at the end of 2027.

WILLIAM BRANGHAM: All right, that is Juliette Cubanski at KFF.

Thank you so much for your insights.

JULIETTE CUBANSKI: Thank you.