What Does Ozempic Do? How Ozempic & Wegovy Cause Weight Loss

Weight loss is an important health goal for Sabrazsia Gardner, so she began researching Wegovy, the anti-obesity drug that contains the same medication as Ozempic.

Gardner, 33, says she wanted to stop the snacking and binge eating that contributed to her obesity and eat less. But diets didn’t work, and she didn’t want to go the weight-loss surgery route.

The effectiveness and increasing popularity of drugs like Wegovy and Ozempic for weight loss are calling attention to the conundrum that Gardner and many others living with obesity face — when making lifestyle changes fails to lead to significant weight loss.

The idea that “(obesity) is a problem of willpower was really an oversimplification,” Dr. Tara Narula, cardiologist at Northwell Health in New York City, said on TODAY in a segment aired Aug. 15. She added that weight loss medications have shown many people, both researchers and patients, that genetics, hormones, environment, the brain and lifestyle choices all contribute to weight gain and loss.

“Lifestyle changes are always the hallmark of how we intervene first, and we teach people about how to eat healthy and also how to move and exercise, but for some people, it’s not enough,” she said.

Previous medications targeting obesity haven’t been “great,” Narula explained, so Wegovy and Ozempic are showing the potential of changing a person’s brain chemistry to impact their obesity.

For example, once Gardner started taking Wegovy in January 2023 after talking about all the options with her doctor, she noticed she had “very little appetite” and finally started losing weight.

“I don’t think about food the same. … I don’t think about snacking, and I’m fuller longer,” Gardner, an esthetician who lives in Chandler, Arizona, tells TODAY.com.

“I don’t even have hunger cravings. I eat because I’m supposed to. You eat to live, not live to eat.”

"I don't snack. Once I'm done eating, I don't want something else or I don't want something sweet. I don't have any type of cravings," Sabrazsia Gardner says of her experience with the anti-obesity drug Wegovy.
“I don’t snack. Once I’m done eating, I don’t want something else or I don’t want something sweet. I don’t have any type of cravings,” Sabrazsia Gardner says of her experience with the anti-obesity drug Wegovy.Courtesy Sabrazsia Gardner

Gardner could once eat 10 chicken wings in a sitting, but barely ate three when she recently treated herself. She got a stomachache afterward, one of the side effects she’s experienced on the drug. Since starting Wegovy, Gardner has also had fatigue, diarrhea and “really prominent” nausea for which she takes another medication.

Gardner says she sometimes doesn’t feel hungry all day and is no longer drawn to chips or chocolate — foods she used to crave and snack on. She’s lost 10 pounds so far.

What’s the difference between Ozempic and Wegovy?

Wegovy contains semaglutide, the same medication found in Ozempic, the Type 2 diabetes treatment that comes with a celebrated side effect: weight loss.

The only difference between the two drugs is the design of the injector pen and the doses, says Dr. Louis Aronne, an obesity medicine physician and director of the Comprehensive Weight Control Center at Weill Cornell Medicine and NewYork-Presbyterian.

Can you take Ozempic just for weight loss?

Wegovy is approved for weight loss by the U.S. Food and Drug Administration, while Ozempic is not, though many people are using it off-label for that purpose. Each medication is self-injected by patients once a week.

Wegovy comes in five different dose strengths, while Ozempic has four.

The maximum dose is 2 milligrams for Ozempic and 2.4 milligrams for Wegovy, according to Novo Nordisk, the pharmaceutical giant that makes both drugs. The company says they are not interchangeable.

How do Ozempic and Wegovy lead to weight loss?

Semaglutide is a synthetic version of a hormone known as GLP-1, which the body releases into the intestine when people eat food, says Aronne, who is a scientific adviser for Novo Nordisk.

When the medication hits GLP-1 receptors in different parts of the brain, that triggers a reaction, stimulating nerves that mimic the effect of eating food — people have reduced appetite, and when they do eat, they feel full sooner, he notes.

“That hormone gets absorbed into the bloodstream, goes to the brain and tells the brain you’ve eaten food. So people basically feel like they’ve already eaten when they take it,” Aronne tells TODAY.com.

“It’s kind of like if I gave you Thanksgiving dinner and then I asked you to eat another dinner. You’ll say, ‘I can’t possibly eat it. I just ate a whole dinner.’”

Another way the medication works is that it slows down stomach emptying, which slows down the absorption of calories and may contribute to the feeling of fullness, Aronne says.

Some experts also believe Ozempic and Wegovy target the “disease mechanism” of obesity, or its underlying causes, Dr. Ania Jastreboff, associate professor at Yale School of Medicine and obesity medicine physician-scientist, tells TODAY.com. Jastreboff is on the scientific advisory board for Novo Nordisk and has led semaglutide clinical trials at Yale funded by Novo Nordisk.

Obesity as a disease is tied to what Jastreboff calls the “defended fat mass set point.”

“Our body wants to carry energy, and it carries that energy in the form of fat,” she explains. “It doesn’t want us to carry not enough energy because then we would starve, and it doesn’t want us to carry too much energy because then we wouldn’t be able to do everything that we do every day. There’s a sweet spot, and we call it the defended fat mass set point.”

Because the factors that can contribute to obesity, such as highly processed foods and inactive lifestyles, are more common than ever in today’s environment, on a population level, the U.S.’s defended fat mass set point has increased, Jastreboff says. For example, if you have a BMI of 31 in 2022, 100 years ago, it might’ve been a 22.

About 42% of the population has obesity, meaning they have a chronic disease “where the body wants to carry extra fat,” she adds.

Semaglutide reregulates the patient’s defended fat mass set point to a healthier place, Jastreboff says. “We are decreasing their defended fat mass set point, and the consequence of that is that they lose weight.”

How much weight can you lose on Ozempic or Wegovy?

In randomized clinical trials, patients receiving the 2.4 milligram dose of semaglutide lost a mean of 6% of their weight by week 12 and 12% of their weight by week 28, researchers reported.

In one study of almost 2,000 overweight or obese adults without diabetes, people taking that dose of semaglutide lost an average of 34 pounds in less than 16 weeks, compared to 6 pounds among those receiving a placebo, NBC News reported.

That same study, funded by Novo Nordisk, showed participants lost about 15% of their body weight after taking semaglutide for 16 months, compared to a 2.4% weight loss for those taking a placebo.

Wegovy should be used in addition to a reduced calorie diet and increased physical activity, the FDA says.

Will Ozempic or Wegovy reduce belly fat?

The answer appears to be yes. That Novo Nordisk-funded study of almost 2,000 overweight or obese adults without diabetes also found their visceral fat — the type that accumulates in the belly — was reduced from baseline with semaglutide, along with their total fat mass.

How do people feel about food when taking semaglutide?

A typical anecdote Aronne hears from a patient is: “I went to the same restaurant I always go to, I ordered the same dinner I always order, but when I ate half of it, I just couldn’t continue. I felt so full, so bloated that I could not eat anymore.”

People with binge eating problems or who obsessively think about food tell him, “I have so much time in the day now because I’m not thinking about my next meal all the time.”

Some people also lose cravings. “Looking at a bag of Doritos was kind of like looking at a pair of socks,” Shea Murray, who used Ozempic, previously told TODAY.

People have to keep taking semaglutide for the drug to keep working — otherwise, they will regain two-thirds of their prior weight loss, studies have shown. It’s not a short-term cosmetic fix for someone who wants to lose 10 pounds to look good in a swimsuit, but a long-term treatment for people who have health problems related to obesity, doctors say.

Why do patients experience nausea?

The most common side effects of Ozempic and Wegovy include nausea, diarrhea, vomiting, stomach pain and constipation, according to Novo Nordisk.

Some patients told NBC News the side effects were so severe they stopped taking the drugs or questioned whether they could stay on them long-term.

In clinical trials, almost 7% of patients treated with Wegovy permanently stopped taking it because of adverse reactions, or more than twice the number of people who received a placebo, Novo Nordisk reported.

The nausea, which was the most common side effect that led patients to stop treatment, may be caused by the slowing down of the emptying of the stomach or by acid reflux, Aronne says. People respond in different ways to the medication, so they must start with the lowest dose and work their way up to higher doses slowly, he adds.

What foods should be avoided in the Ozempic diet?

Patients taking semaglutide should notice which foods may exacerbate their symptoms and eat less of those, says Jastreboff.

One Ozempic patient previously told TODAY.com that greasy food in general was “really hard” for her to eat after starting the medication.

To reduce nausea while on semaglutide, registered dietitian Emily Rubin recommended skipping hot, fried or greasy food; and avoiding eating or cooking strong-smelling food.

Don’t eat too quickly and don’t have a large drink with meals, she says.

Do you regain weight after stopping Ozempic or Wegovy?

Because Ozempic is not approved for weight loss, it wasn’t studied for “weight changes following discontinuation,” Novo Nordisk previously told TODAY.

Data from its clinical trials for Wegovy “showed that, not unexpectedly, patients experience weight regain once they stop taking the medication,” the company previously said in a statement to TODAY.com.

“This supports the belief that obesity is a chronic disease that requires long-term management, much like high blood pressure or high cholesterol, for which most patients remain on therapy long term in order to continue to experience the benefits of their medications.”

What are the dangers of Ozempic and Wegovy?

Possible serious side effects of Ozempic and Wegovy include pancreatitis, gallbladder problems and kidney problems, among other issues, according to the manufacturer.

Both drugs also carry the warning that semaglutide causes thyroid C-cell tumors in rodents, though it’s unknown whether that can happen in humans.

Dr. Robert Lustig, a neuroendocrinologist and professor emeritus of pediatrics at the University of California, San Francisco, previously told TODAY.com he has “major, major concerns” about people potentially taking Wegovy for years or for life. He’s not against the drug, but calls it a Band-Aid that’s not fixing the root of the problem of obesity.

If people keep eating junk food and not exercising, the drug is not going to solve any problems, adds Dr. Luigi Fontana, professor of medicine and nutrition, and director of the healthy longevity research program at The University of Sydney in Australia.

Dr. Zhaoping Li, professor of medicine and chief of the division of clinical nutrition at the University of California, Los Angeles, says more long-term data is needed about Wegovy.

But other doctors previously told TODAY.com they were comfortable prescribing it for the long-term. Aronne calls this “the golden age of treating obesity” as more medications that work and are safe become available, he says.

Sabrazsia Gardner, the woman who started taking Wegovy in January, says she’d like to stay on it for as long as she can and hopes to lose 120 pounds.

“The nausea I can live with. It’s annoying, but it’s OK. If it’s making me healthier, I think I’ll be OK,” she says.


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