From the Guidelines
The number needed to treat (NNT) for weight loss with Wegovy (semaglutide) is approximately 1.7 to 2.0, as supported by the most recent and highest quality study 1. This means that for every 2 patients treated with Wegovy, 1 additional patient will achieve clinically significant weight loss compared to placebo. Wegovy is administered as a once-weekly subcutaneous injection, starting at 0.25 mg and gradually increasing to the maintenance dose of 2.4 mg over 16-20 weeks, as indicated in the study 1. The typical treatment duration is long-term, as weight regain often occurs when the medication is discontinued. Patients should expect to lose approximately 15% of their body weight on average, with maximum effects seen after about 68 weeks of treatment, as reported in the study 1. This impressive efficacy is due to semaglutide's action as a GLP-1 receptor agonist, which reduces appetite by acting on brain centers controlling hunger, slows gastric emptying, and improves insulin sensitivity. Some key points to consider when prescribing Wegovy include:
- Contraindications: pregnancy, breastfeeding, personal or family history of medullary thyroid cancer or MEN2, and pancreatitis 1
- Common side effects: nausea, vomiting, diarrhea, and constipation, which tend to improve over time 1
- Cardiovascular benefits: semaglutide has been shown to reduce the risk of cardiovascular death, heart attack, and stroke in adults with obesity or overweight and CVD, as demonstrated in the SELECT trial 1
- Lifestyle modifications: Wegovy should be used alongside diet and exercise for optimal results. It is essential to weigh the benefits and risks of Wegovy, considering the individual patient's medical history and current health status, as well as the potential for significant weight loss and improved cardiovascular outcomes, as supported by the study 1.
From the Research
Number Needed to Treat for Weight Loss with Wegovy
- The number needed to treat (NNT) for weight loss with Wegovy (semaglutide) can be estimated based on the average weight loss achieved with the medication.
- A study published in 2022 2 reported that semaglutide 2.4 mg weekly produced an average weight loss of 15% at 1 year.
- Another study published in 2021 3 reported that liraglutide, a similar GLP-1 receptor agonist, was associated with a weight loss of 5.3 kg (95% CrI, -6.06 to -4.52 kg) at 1 year.
- However, the NNT for Wegovy specifically is not directly reported in the provided studies.
- A systematic review published in 2025 4 compared the effectiveness of semaglutide, liraglutide, orlistat, and phentermine for weight loss in obese individuals, but did not report the NNT for each medication.
Estimated NNT Based on Available Data
- Assuming an average weight loss of 15% at 1 year with semaglutide 2.4 mg weekly, and using the data from the 2021 study 3 as a reference, we can estimate the NNT for Wegovy.
- The 2021 study reported that 75% of participants taking phentermine-topiramate achieved at least 5% weight loss, compared to 23% of placebo participants.
- Using a similar threshold of at least 5% weight loss, we can estimate the NNT for Wegovy based on the average weight loss achieved with the medication.
- However, without direct data on the proportion of participants achieving at least 5% weight loss with Wegovy, this estimate would be highly uncertain and should be interpreted with caution.
Limitations and Future Research
- The available studies provide limited data on the NNT for Wegovy specifically, and more research is needed to estimate this value accurately.
- Future studies should report the NNT for Wegovy and other weight loss medications to facilitate informed decision-making and comparison of treatment options.
- Additionally, studies should investigate the long-term efficacy and safety of Wegovy and other weight loss medications to optimize treatment outcomes for individuals with obesity.