Do medicines like weight loss drug ozempic work?

Lauren Ball, The University of Queensland and Emily Burch, Southern Cross University

Hundreds of thousands of people worldwide are taking drugs like Ozempic to lose weight. But what do we actually know about them? This month, The Conversation’s experts explore their rise, impact and potential consequences.


After weight-loss drugs like Ozempic exploded onto the market, celebrities and social media influencers were quick to spruik their benefits, leading to their rapid rise in use. In the last three months of 2022, clinicians in the United States alone wrote more than nine million prescriptions for these drugs.

As they’ve grown in popularity, we’ve also heard more about the potential side effects – from common gastrointestinal discomforts, to more serious mental health concerns.

But what does the science say about how well Ozempic and Wegovy (which are both brand names of the drug semaglutide) work for weight loss? And what are the potential side effects? Here’s what to consider if you or a loved one are thinking of taking the drug.

Potential benefits

1) It’s likely to help you lose weight

The largest, well-conducted research study of semaglutide was from United Kingdom in 2021. Some 1,961 people who were classified as “overweight” or “obese” were randomly assigned to have either semaglutide or a placebo and followed for 68 weeks (about 1.3 years). All participants also had free access to advice about healthy eating and physical activity.

The study found those taking semaglutide lost weight – significantly more than people who had the placebo (-14.9% of their body weight compared with -2.4% of body weight).

In another study in the United States, one health-care clinic gave 408 people weekly injections of semaglutide. Over the first three months, those included in the final analysis (175 people) lost an average of 6.7kg. Over the first six months, they lost an average of 12.3kg.

Large weight losses have been found in a more recent trial of semaglutide, suggesting weight loss is a very likely outcome of ongoing use of the medication.

Man stands on scales
People taking semaglutide in the trial lost just under 15% of their body weight, on average, compared with 2.4% for those taking a placebo. John Hanson Pye/Shutterstock

2) It may reduce your chronic disease risk factors

When people in the overweight or obese weight categories lose at least 5% of their body weight, physiological changes often occur beyond a change in weight or shape. This might include lowered cholesterol levels, lowered blood pressure and lowered blood glucose levels, which all reduce the risk of chronic diseases.

In one of the semaglutide trials, most people (87.3%) lost at least 5% of their body weight. Although most of the large studies of semaglutide excluded people with metabolic health conditions such as type 2 diabetes, metabolic health gains were observed, including lowered blood pressure, blood glucose levels and fasting blood lipid (fat) levels.

In the UK study from 2021, people taking semaglutide had greater improvements in physical capabilities and risk factors for heart disease and diabetes, including reductions in waist circumference, markers of inflammation, blood pressure and blood glucose levels.

3) It might improve your quality of life, emotional wellbeing or sense of achievement

The original trial of semaglutide did not focus on this bundle of benefits, but further follow-ups show additional benefits associated with the medication. Compared to the placebo, people taking semaglutide saw significant improvements in their physical functioning and perceptions of their general health, social functioning and mental health.

Anecdotally (not based on scientific research), people using semaglutide, such as Oprah Winfrey, report a reclaiming or turning point of their life, social situation and body image.

What about the risks?

1) You may experience gastrointestinal symptoms

In the US clinical trial, nearly half (48.6%) of people taking semaglutide reported experiencing adverse effects. Nausea and vomiting were the most frequently experienced (36.6%) followed by diarrhea (8.6%), fatigue (6.3%) and constipation (5.7%).

In the UK study, nausea and diarrhoea were also commonly reported.

In another trial, many participants (74.2%) using semaglutide reported gastrointestinal symptoms. However, nearly half (47.9%) using the placebo also reported gastrointestinal symptoms, indicating that symptoms may be similar to those experienced during normal daily living.

Most gastrointestinal symptoms were mild to moderate in severity, and resolved for most people without the need to stop participating in the study.

2) You might feel fatigued

Fatigue was the second most common side effect for participants in the US clinical trial, affecting 6.3% of participants.

Person holds Ozempic injection
The most common symptoms are gastrointestinal, followed by fatigue. fcm82/Shutterstock

3) You might be among the minority who don’t tolerate the drug

Australia’s Therapeutic Goods Administration (TGA) has approved Ozempic as safe to use, for the treatment of type 2 diabetes but it has not yet been approved for weight loss. The TGA has also approved Wegovy (a higher dose of semagtlutide) for weight loss, however it’s not yet available in Australia.

In the US clinical trial, no unexpected safety issues were reported. However, five patients (2.9%) had to stop taking the medication because they could not tolerate the adverse effects. Fifteen (8.6%) had to either reduce the dose or remain on the same dose to avoid the adverse effects.

In other studies, some patients stopped the trial due to gastrointestinal symptoms being so severe they could not tolerate continuing.

More severe safety concerns reported in studies include gallbladder-related disorders (mostly cholelithiasis, also known as gallstones) in 34 patients (2.6%) and mild acute pancreatitis in three patients (0.2%). All people recovered during the trial period.

A 2024 European study analysed psychiatric adverse events associated with semaglutide, liraglutide and tirzepatide (which work in a similar way to semaglutide). Between January 2021 and May 2023, the drug database recorded 481 psychiatric events (about 1.2% of the total reported) associated with these drugs. About half of these events were reported as depression, followed by anxiety (39%) and suicidal ideation (19.6%). Nine deaths and 11 life-threatening outcomes were reported during the study period.

Due to the severity and fatal outcomes of some of these reports, the US Food and Drug Administration investigated further but did not find evidence that use of these medicines caused suicidal thoughts or actions.

4) It might be difficult to access

Despite being considered safe, the TGA has warned significant Ozempic access barriers are likely to continue throughout 2024.

To manage the shortage, pharmacists are instructed to give preference to people with type 2 diabetes who are seeking the medication.

5) You might not always get clear information from vested interests

Given the popularity of Ozempic and Wegovy, health organisations such as the World Obesity Federation have expressed concern about the medication’s marketing, PR and strong social media presence.

Some journalists have raised conflict of interest concerns about the relationship between some obesity researchers and Novo Nordrisk, Ozempic and Wegovy’s manufacturer. The worry is that researchers might be influenced by their relationship with Novo Nordrisk to produce study results that are more favourable to the medications.

Bottom line

Ozempic is a medication that should be used in conjunction with your health care provider. But remember, weight is only one aspect of your health and wellbeing. It’s important to take a holistic view of your health and prioritise eating well, moving more and getting enough sleep.


Read the other articles in The Conversation’s Ozempic series here.

Lauren Ball, Professor of Community Health and Wellbeing, The University of Queensland and Emily Burch, Lecturer, Southern Cross University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

You might also be interested in these articles:

How to lose 5kg: Here’s how I did it in 6 weeks

How to lose weight: The start of my weight loss journey

Sign up to feel-good emails.

Get health and wellbeing inspiration delivered straight to your inbox.

    Leave a Reply

    Your email address will not be published. Required fields are marked *