The Wegovy STEP 4 trial: what the evidence actually shows

The biggest misconception: that STEP 4 showed Wegovy 'stops working'

A common misreading of the STEP 4 data is that the regain seen after stopping semaglutide means the medicine has failed. That gets it the wrong way round. What the trial actually demonstrated is that semaglutide works precisely because it acts on appetite-regulating pathways in the brain and gut — pathways that return to their previous state once the medicine is withdrawn. Regain is not a sign of treatment failure; it is a predictable consequence of stopping a medicine that was doing its job.

The trial enrolled 803 adults who had already completed a 20-week single-blind run-in phase on subcutaneous semaglutide 2.4mg. By the point of randomisation they had lost an average of around 10.6% of their starting body weight. Half then continued on semaglutide for a further 48 weeks; half were switched to placebo while maintaining the same lifestyle support. By week 68, those who continued treatment had lost a further 7.9% of body weight on average, bringing total mean loss to roughly 17.4%. Those who stopped regained approximately 6.9% — ending about 5% below where they started. The trial did not show that the medicine had stopped working. It showed the opposite. Semaglutide's mechanism of action explains why this pattern is expected.

The important practical message is that weight management with these medicines is an ongoing clinical conversation, not a fixed course. Stopping is a clinical decision, not a default, and one to make with your prescriber rather than independently.

What STEP 4 measured that other STEP trials did not

The broader STEP programme covered a range of questions: initial efficacy, effects in people with type 2 diabetes, effects in people with cardiovascular disease, and so on. STEP 1 is the headline efficacy trial most people encounter first, showing approximately 15% average weight loss over 68 weeks at the 2.4mg maintenance dose. STEP 4 was designed specifically to answer a different question: what happens at the point of stopping?

That distinction matters clinically. A question our prescribers hear most weeks is some version of "do I have to stay on this forever?" STEP 4 is the trial that gives an evidence-based answer rather than a guess. The data showed that cardiometabolic markers (blood pressure, waist circumference, blood glucose, lipid levels) also worsened on average in the group who switched to placebo, and improved in those who continued. Weight is not the only variable that tracked with treatment status.

This is also the trial that informs current clinical thinking around treatment duration. The semaglutide STEP 4 findings are cited in discussions about whether weight-management medicines should be considered long-term rather than short-term interventions, a framing that is increasingly reflected in NICE guidance and NHS commissioning decisions. The semaglutide overview covers how the wider evidence base shaped Wegovy's UK licence.

How STEP 4 fits into what Wegovy is licensed to do in the UK

Wegovy (semaglutide 2.4mg) is licensed in the UK for weight management in adults with a BMI of 30 or above, or 27 or above alongside a weight-related health condition such as high blood pressure, raised cholesterol or obstructive sleep apnoea, used alongside a reduced-calorie diet and increased physical activity. NHS guidance on semaglutide covers the licensed indications and what to expect from treatment.

NICE's appraisal of semaglutide for weight management (published as TA875) recommends it for use within specialist weight management services for a maximum of two years, reflecting the reality that the evidence for long-term use comes from trials of up to 68 weeks, and that regain after stopping is well documented. For private patients, treatment duration is a clinical question between you and your prescriber, reviewed at each repeat.

An important point on Wegovy's recent development: in April 2026 the MHRA approved a 7.2mg maintenance dose, delivered via a dedicated single-dose pen, for adults with a BMI of 30 or above. STEP 4 was conducted entirely with the 2.4mg dose, so the long-term continuation data does not yet exist at that higher dose, something worth knowing if that option comes up at your consultation. If you want to understand current pricing for private Wegovy treatment, the Wegovy cost page sets out what's typically involved.

What this means if you are considering treatment

STEP 4 reinforces two things that are easy to underestimate at the start of a weight-management journey. First, the biological drivers of weight (appetite signalling, metabolic rate, hormonal responses) are persistent. A medicine that works on them needs to keep working for the effect to hold. Second, the decision to start, continue or stop is a clinical one, not just a personal preference, and it benefits from proper medical review rather than an arbitrary cut-off.

For people considering Wegovy through a regulated private service, the full Wegovy guide covers eligibility, how titration works, and what the clinical review process involves. If you'd like to understand how this fits into weight management more broadly, the weight loss treatment overview is a practical starting point. Both medicines available through nume (Wegovy and Mounjaro) are prescription-only and assessed individually by a GPhC-registered prescriber before any treatment is confirmed. When you're ready to take that step, you can start your free consultation and have your answers reviewed the same day by a named clinician, not an automated system.