As prescriptions for popular weight loss drugs have soared, the class of medications known as GLP-1 agonists is changing the way people think about how to lose weight.
Initially developed to treat type 2 diabetes, medications like semaglutide and tirzepatide have also been shown to be effective in promoting weight loss. The US Food and Drug Administration has now approved both medications for treatment of patients with obesity, even if they do not have diabetes.
What should people consider if they want to start taking these medications? How effective are they? What are some possible side effects? Where should people obtain the drugs — and which places should they avoid?
To help us with these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at the George Washington University. She previously served as Baltimore’s health commissioner.
CNN: What should people consider in deciding whether they should start these medications?
Dr. Leana Wen: Let’s begin with the eligibility criteria for these medications. Both semaglutide and tirzepatide are approved for two indications: type 2 diabetes and obesity. The medications approved by the FDA for use in diabetes are called Ozempic and Mounjaro, which are the brand names of semaglutide and tirzepatide, respectively. The same medications also are approved for treating obesity under the brand names Wegovy and Zepbound.
The FDA approved Wegovy and Zepbound for weight loss in two specific circumstances. Individuals are eligible if they are adults who have a body mass index of at least 30, which is classified as having obesity. Adults also can qualify if they have a BMI of 27 or greater, which puts them in the category of being overweight, if they also have at least one weight-related condition such as diabetes, hypertension or high cholesterol. For Wegovy, patients who are 12 and older with a BMI in the 95th percentile for age and sex are also eligible.
I want to clarify two things here. First, just because someone is eligible does not mean that these medications are always the right options for them. These are weekly injections that, depending on insurance coverage, could be quite costly and therefore inaccessible to many. Also, some people would do well without medications and could have sufficient weight loss with changes in diet and exercise.
Moreover, these medications are intended to be taken for years, possibly a lifetime. Some studies have shown that individuals who stop the medications regain most of the weight loss. Importantly, the medications are meant to be taken in conjunction with lifestyle changes, so they are not meant to be a “quick fix” for people who are unwilling to improve their diet and fitness. These are all considerations patients need to discuss with their physicians when deciding whether to start the medications.
Second, it’s important to emphasize that these medications are intended to treat health conditions. Obesity is a chronic medical condition that predisposes the individual to many negative health effects, including increased rates of cardiovascular disease culminating in stroke and heart attacks. People with obesity also experience higher rates of back and joint pain, sleep apnea and depression. Medications can be of great help to patients who have the medical condition of obesity, or who are overweight and already diagnosed with weight-related chronic conditions. These injections are not intended for people who want to lose weight on a short-term basis solely for nonmedical, cosmetic purposes.
CNN: You mentioned Ozempic and Mounjaro. Can these medications also be used for weight loss?
Wen: The FDA-approved versions of semaglutide and tirzepatide for weight loss are called Wegovy and Zepbound. There have been shortages of these drugs, and doctors have sometimes prescribed Ozempic in place of Wegovy and Mounjaro in place of Zepbound.
This is a practice called off-label prescribing and is allowed. If the medications are prescribed by a physician and filled at a legitimate pharmacy, there should not be a concern, because the active ingredient is the same — they are just called different names.
CNN: How effective are these drugs in reducing weight?
Wen: There is robust evidence in favor of the effectiveness of these drugs. A seminal study on semaglutide that was published in The New England Journal of Medicine found that those who took the medication lost an average of 14.9% of their body weight in about a year. This decrease was significantly greater than those in the placebo group, who lost an average of 2.4% in the same period.
The weight loss may be even greater for tirzepatide. A randomized-controlled trial, also published in The New England Journal of Medicine, found that those taking the higher dose of tirzepatide had a 21.4% reduction in body weight in just over a year—a much higher reduction compared with placebo at 2.5%.
One thing I want to emphasize is that these studies all included lifestyle changes as part of the treatment regimen, too. Individuals in both the medication and placebo arms adhered to a strict diet that had a 500-calorie deficit each day. They also were asked to exercise for at least 150 minutes a week and had access to a nutritionist or other coach. This makes the point that these medications are intended to be used together with lifestyle changes, not in place of them.
CNN: What are some possible side effects?
Wen: Common side effects are gastrointestinal effects. This includes nausea, vomiting, diarrhea and constipation. Some more serious stomach problems also have been reported. The FDA has said that it is reviewing reports of people experiencing hair loss and suicidal thoughts while taking the medications, though a preliminary review of clinical trial results did not turn up an association between medication usage and suicidality.
Longer-term side effects are not known because these are relatively new therapeutics. It’s also not known whether the effectiveness might end up decreasing over time.
CNN: Are there certain medications that preclude you from taking the weight loss drugs at the same time?
Wen: There are some medications that may interact with semaglutide and tirzepatide, including insulins and oral diabetes medications. The dosages of these medications may need to be adjusted. There is also a question of whether the medications could render oral contraceptives less effective, and additional forms of contraception may be needed. And these medications are not recommended for use during pregnancy due to lack of data. These are additional reasons why it’s crucial to speak with your physician to discuss the benefits and potential risks of starting these drugs.
CNN: For those who are interested, where should people obtain these drugs?
Wen: These medications are prescription medications. The decision to start them must be made in consultation with a physician.
People who are thinking of starting these medications should have the conversation with their primary care provider. This is the person who knows them the best and who manages the rest of their medical care. These medications can have tremendous benefit, but they are not for everyone. The expense, possible downsides and side effects must be carefully considered, too.
If you and your physician believe that you should start the medications, you should obtain them from your pharmacy, as you do other medications. The safest version of the drug is the one that is made by the manufacturers, which are Novo Nordisk for semaglutide and Eli Lilly for tirzepatide.
CNN: Some pharmacies advertise that they have “generic” versions of the drugs. Is it safe to buy these versions?
Wen: Both Wegovy and Zepbound are under patent. There are no approved generic versions of these drugs.
The pharmacies advertising that they have so-called generics are referring to a process called compounding. This is where some pharmacies can reformulate medications and sell them. The FDA allows this process when drugs are in shortage, as is the case now. However, the agency has issued warnings about the safety of compounded medications. The medications made by manufacturers are inspected for quality, safety and effectiveness, while the compounded versions are not. People may have easier access to compounded versions, and they could be cheaper, but they should know that taking them comes at higher risk and should use caution.
I want to also warn people against counterfeit medications. This is a very serious problem. The FDA has said that it has seized thousands of units of counterfeit semaglutide, and both manufacturers have warned about the danger of illegal internet pharmacies selling counterfeit medications.
Let me emphasize: Do not buy medications from illegal internet pharmacies. Doing so is very dangerous. You do not know what is in the medications you are purchasing. The dosage could be wrong, the medication could be tainted, and you may not even be getting the drug that you think you bought. The FDA has a website that helps consumers distinguish legitimate pharmacies from rogue outfits that are illegally selling unsafe medications.
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