Is Wegovy more effective than other drugs like Qsymia for long-term weight management?

Wegovy has shown sustained weight loss of around 15% at 68 weeks, and many participants maintained benefits at two years. Qsymia (not licensed in the UK) has demonstrated average losses of 7–10% in US studies, so semaglutide generally produces greater and longer-lasting reductions.

Two different approaches to weight management

Wegovy and Qsymia are often compared because they both feature in discussions about modern weight-loss treatments. Wegovy (semaglutide) is a GLP-1 receptor agonist that works by reducing appetite, slowing digestion, and supporting healthier eating patterns. Qsymia, available in the United States but not licensed in the UK, is a combination of phentermine (an appetite suppressant) and topiramate (a drug used for epilepsy and migraines). Their mechanisms are quite different, reflecting different eras of obesity treatment.

What the evidence says about Wegovy

The STEP clinical programme provides the clearest picture of Wegovy’s effectiveness. In the STEP-1 trial, published in The New England Journal of Medicine, people using semaglutide 2.4 mg weekly lost on average about 15% of their body weight over 68 weeks when combined with lifestyle support. Longer-term evidence from STEP-5 showed that these reductions could be sustained over two years, demonstrating that semaglutide can deliver not just short-term success but lasting weight management when treatment continues.

What the evidence says about Qsymia

Qsymia has been tested in US-based studies such as CONQUER and SEQUEL. These trials reported average weight loss of around 7–10% at one year, with some participants maintaining benefits at two years. While these outcomes are meaningful, they are generally smaller than those seen with Wegovy at full dose. The combination of phentermine and topiramate can be effective, but tolerability and safety have been ongoing concerns, limiting its wider adoption outside the US.

Safety and tolerability

The safety profiles of the two drugs differ sharply. Qsymia contains phentermine, which can raise blood pressure and heart rate, and topiramate, which has been associated with cognitive side effects such as memory or concentration problems. Because of these risks, Qsymia has not been licensed in the UK or Europe. Wegovy, while not free of side effects, has a safety profile that is generally manageable. Gastrointestinal symptoms like nausea and diarrhoea are the most common, and trials showed that only a minority of participants needed to stop treatment because of them.

NHS and regulatory perspective

In the UK, NICE approved Wegovy in 2023 for adults with a BMI over 35 and weight-related conditions, or in some cases above 30, to be used within NHS specialist services. Qsymia is not available on the NHS or privately in the UK, reflecting the regulatory decision not to license it due to safety and cost-effectiveness concerns. This means that for people in the UK, Wegovy is the clear option where eligibility criteria are met.

Why long-term data matters

A key strength of Wegovy is the durability of its results. The STEP-5 trial showed that weight loss was not only significant but also sustained for two years with ongoing treatment, which is crucial given that obesity is a long-term condition. Qsymia has demonstrated some long-term benefit too, but concerns about side effects and its lack of approval outside the US limit its role in global practice.

Key takeaways

Comparing the two, Wegovy offers greater average weight loss and stronger evidence for long-term safety and effectiveness. Qsymia can be effective in some contexts but is not available in the UK due to regulatory concerns. For long-term weight management, semaglutide stands out as the better-supported option, both in terms of results and accessibility through NHS services.