Wegovy stats: what the clinical trial numbers actually show

What did the STEP 1 trial actually measure?

STEP 1 randomised 1,961 adults without type 2 diabetes, all with a BMI of 30 or above (or 27 or above with at least one weight-related condition), to either semaglutide 2.4 mg or a placebo, weekly by injection, over 68 weeks. Everyone in the trial also received structured lifestyle counselling. That last point matters more than it sometimes gets acknowledged: the medicine was tested alongside support, not instead of it.

The average weight reduction in the semaglutide group was around 14.9% of starting body weight, equivalent to roughly 15 kg for a person starting at 100 kg. Around 86% of participants on semaglutide lost at least 5% of their weight; around a third lost 20% or more. So while 15% is the figure most often cited, the distribution beneath it is wide. Some people lost considerably less; a meaningful proportion lost considerably more.

The placebo group, also receiving lifestyle support, lost an average of around 2.4%. The difference between groups (not just the semaglutide result in isolation) is the clinically meaningful number. You can read the full data in the STEP 1 paper in the New England Journal of Medicine.

Does the new 7.2 mg dose change the numbers?

It does, modestly but meaningfully. On 14 April 2026 the MHRA approved a dedicated single-dose 7.2 mg Wegovy pen (one pre-set weekly injection) for adults with a BMI of 30 or above. Trial data at that dose reported an average weight loss of around 20.7% over 72 weeks, which starts to approach the results seen with tirzepatide at its highest doses in the SURMOUNT programme.

The 7.2 mg dose is the maximum. Starting dose remains 0.25 mg, titrated upwards roughly every four weeks by the prescriber. The official approval announcement is on GOV.UK. Whether a patient moves to 7.2 mg depends on tolerability and response at lower doses, that decision sits with the prescriber, not the patient. If you're exploring what treatment options are available to you, our overview of what Wegovy is used for sets out the licensed indications clearly.

One thing the stats can't tell you: whether 7.2 mg will be the right dose for any individual. Titration exists for a reason. The body's response to semaglutide varies, and many people reach a dose below the maximum that works well for them.

How do Wegovy's figures compare with what else is on offer?

A common misconception is that all GLP-1 weight-loss medicines produce roughly the same result. The trial data suggests otherwise. At 2.4 mg, semaglutide's ~15% average sits below what tirzepatide produced in SURMOUNT-1 (around 20–21% at 15 mg), a gap confirmed in the SURMOUNT-5 head-to-head trial published in 2025. The 7.2 mg semaglutide data narrows that gap considerably, which is why the approval of the higher dose shifted the conversation.

Wegovy is also now approved in the UK for reducing the risk of major cardiovascular events in eligible adults, and from July 2026 holds a conditional approval for a form of fatty liver disease (MASH). Weight loss is one part of a broader clinical picture. For a fuller look at how the two licensed injectable treatments sit alongside each other, the semaglutide overview on this site covers the mechanism and the evidence base in more depth.

On cost, private prices for Wegovy vary by dose and provider. If that's on your mind, a grounded look at what's involved is on the Wegovy cost and pricing page. The NICE assessment of semaglutide for weight management (NICE TA875) sets out the evidence review that underpins NHS commissioning decisions, and is worth reading if you want the full regulatory picture.

What do the stats not capture?

Trial populations are selected. STEP 1 excluded people with certain medical histories, and like all phase-3 studies it ran under conditions (regular check-ins, structured support, motivated participants) that don't always mirror everyday life. That's not a criticism; it's just how drug trials work, and it's why real-world results can look different from headline percentages.

The stats also don't capture what happens when the medicine stops. Wegovy is not a permanent fix: weight tends to return after stopping, which is consistent with what we understand about how obesity works as a condition. The background on Wegovy covers the mechanism behind this honestly. NICE's guidance notes a maximum treatment duration of two years for semaglutide within NHS specialist services, which itself reflects the evidence horizon of the trials.

None of this makes the statistics less real. It makes them more useful when read carefully. Our detailed statistics breakdown goes further into the subgroup data for anyone who wants the deeper cut. And if you're thinking about whether treatment might suit your own circumstances, including practical questions such as whether you can take Wegovy alongside statins, our prescribers are the right people to talk to, not a percentage on a page.