What Wegovy Studies Tell Us About Semaglutide and Weight Loss

STEP 1: the foundational semaglutide study that set the benchmark

The STEP 1 trial recruited 1,961 adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition, who did not have type 2 diabetes. Participants received once-weekly semaglutide 2.4 mg or placebo alongside lifestyle guidance over 68 weeks. The semaglutide group lost an average of roughly 15% of body weight; the placebo group lost around 2.4%. Around a third of participants on the active treatment lost more than 20% of their starting weight.

One misconception worth clearing up gently: many people assume these results are typical of the first few months. In practice, weight loss accumulates gradually across the titration period and beyond — the 15% figure reflects the full 68-week course, not a quick transformation early on. The STEP 1 study breakdown covers how the trajectory looked across the trial period.

It is also worth noting that STEP 1 participants followed a structured lifestyle programme. Real-world results vary. That honest caveat does not diminish the evidence, it contextualises it, which is exactly what a prescriber does during a clinical review.

Beyond weight: what the SELECT and STRIDE semaglutide studies found

Weight loss was never the only research question. The SELECT trial enrolled over 17,000 adults with pre-existing cardiovascular disease and a BMI of 27 or above (but without diabetes) to test whether semaglutide reduced cardiovascular events. It did: a statistically significant reduction in heart attack, stroke and cardiovascular death compared with placebo over a median of around three years. This is why Wegovy also holds a licensed cardiovascular indication in the UK, separate from its weight-management licence.

The SELECT trial findings are clinically important because they shift the conversation about weight-loss medicines from aesthetics to metabolic health outcomes. For eligible patients, a prescriber might weigh that evidence directly. The STRIDE study explored mobility and physical function as outcomes, finding improvements in physical activity capacity alongside weight reduction, a finding relevant to people for whom joint pain or breathlessness is a driver of seeking treatment.

The NHS patient information for semaglutide reflects the licensed indications that emerged from this broader evidence base.

The higher-dose data: 7.2 mg and where the evidence stands now

The original Wegovy programme established 2.4 mg as the maintenance dose. More recently, Novo Nordisk pursued a higher 7.2 mg dose. On 14 April 2026, the MHRA approved a single-dose 7.2 mg pen, following earlier approval of the dose itself in January 2026. Trial data for 7.2 mg reported average weight loss of around 20.7% over 72 weeks, figures that start to approach the results seen with tirzepatide at its highest dose in the SURMOUNT-5 head-to-head.

The 7.2 mg dose applies to the Wegovy injection and is licensed for adults with a BMI of 30 or above only, the cardiovascular indication is not included at this dose. Starting dose remains 0.25 mg, titrated upward by the prescriber over several months; 7.2 mg is the maximum. For a broader look at how the Wegovy weight-loss trial programme fits together, including the longer-term maintenance data, that page goes into more detail.

If you are curious how private treatment costs compare once you factor in what is included, the Wegovy price comparison guide sets out what different providers typically charge and what those prices do and do not cover.

Safety signals to know from the research programme

The trial programme also generated the safety data that informs current UK guidance. Gastrointestinal effects (nausea, diarrhoea, constipation, vomiting) were the most common adverse events across STEP trials, reported most often around dose increases and generally settling over time. These are listed in full on the semaglutide overview page.

One signal that attracted regulatory attention after the trials concluded: in January 2026 the MHRA issued a Drug Safety Update highlighting acute pancreatitis as an infrequent but potentially serious risk across GLP-1 medicines, including semaglutide. The guidance is straightforward, severe or persistent stomach pain, particularly pain that spreads toward the back, requires prompt medical attention. Suspected side effects can be reported directly at the MHRA's Yellow Card scheme.

There is also a named vision-related signal from a specific analysis: a study examining a possible association between semaglutide and a rare eye condition generated headlines in 2024. The MHRA and NHS are monitoring this; if you have pre-existing eye conditions, it is one to discuss with a prescriber before starting. The overall benefit-risk profile, assessed by both the MHRA and NICE, supports the medicine's use for eligible adults, but that assessment is for a prescriber to apply to your history, not for a webpage to do.