Semaglutide Transformations: What Clinical Trials Tell Us

What STEP 1 actually measured, and what the numbers mean

The STEP 1 study, published in the New England Journal of Medicine, recruited 1,961 adults with obesity or overweight plus at least one weight-related condition, none of whom had type 2 diabetes. Participants were randomised to semaglutide 2.4mg weekly or placebo alongside lifestyle support. After 68 weeks, the semaglutide group had lost an average of 14.9% of their starting body weight, compared with 2.4% on placebo. Roughly a third of participants lost more than 20%, a level previously associated only with bariatric surgery.

These figures describe averages across a trial population. Some people lost considerably more; some lost less. Starting BMI, how quickly someone titrated to the maintenance dose, and how consistently they maintained reduced-calorie eating all influenced individual results. The trial also required participants to attend regular lifestyle counselling sessions, so the transformations reported reflect semaglutide plus structured support, not the injection alone.

One practical point worth absorbing: the titration schedule matters. Treatment opens at 0.25mg and steps upward over roughly four months before reaching 2.4mg maintenance. The early weeks are an adjustment period, not the point at which meaningful weight change tends to begin. Patients who stop during titration because results feel slow are often leaving before the medicine has reached its working dose. If you want a thorough grounding in how the treatment works, our page covering information about Wegovy covers the full picture from dosing through to what to expect over time.

The 7.2mg data, does a higher dose produce a bigger Wegovy transformation?

Since STEP 1, Novo Nordisk developed a higher maintenance dose. The MHRA approved 7.2mg semaglutide (Wegovy) on 14 April 2026, initially supplied as three 2.4mg pens weekly and now also available as a dedicated single-dose pen. Trial data at this higher dose reported average weight loss of around 20.7% over 72 weeks, meaningfully above the 15% seen at 2.4mg. The MHRA's approval was for adults with BMI of 30 or above, the cardiovascular and MASH indications that semaglutide also holds are separate, and the 7.2mg dose applies specifically to the weight-management licence.

Whether the 7.2mg dose is appropriate depends on individual clinical assessment: how someone tolerated earlier dose steps, their medical history, and whether the prescriber considers a higher target dose suitable. Specific dose availability is confirmed at consultation rather than assumed in advance. For a full outline of what semaglutide is licensed for in the UK, the semaglutide prescribing information page covers the detail.

The gap between 7.2mg semaglutide results and tirzepatide 15mg results has narrowed with the newer data, though a direct head-to-head at these updated doses has not yet been published. NICE's appraisal of tirzepatide (TA1026) noted that indirect comparisons favour tirzepatide at equivalent durations, but the picture continues to evolve.

Side effects that come alongside the transformation

The body-weight changes in semaglutide trials did not occur without side effects. In STEP 1, gastrointestinal symptoms (nausea, vomiting, diarrhoea, constipation) were the most commonly reported, and they were more frequent on semaglutide than on placebo. Most were mild to moderate and tended to settle within the first few weeks, particularly after each dose increase. Starting low and titrating gradually is the main reason the schedule is designed the way it is.

A small number of participants in trials discontinued because of GI side effects. The NHS semaglutide medicines page lists the common and uncommon side effects in plain language and is a reliable first reference. Acute pancreatitis is an infrequent but more serious concern: severe stomach pain that radiates toward the back, with or without vomiting, warrants prompt medical assessment. Any patient experiencing this should contact their GP or call 111 without delay, and report unexpected reactions through the MHRA Yellow Card scheme.

Changes in appetite can also affect eating patterns in ways that feel unfamiliar. Many people on semaglutide find that meal sizes drop naturally and that foods they previously found irresistible feel less compelling. Maintaining adequate protein and fluid intake during this period matters more than most people realise, and it is worth raising with a prescriber at each review. Our Wegovy patient information page covers the practical side of managing treatment day to day. Breakfast before the morning injection used to be a non-negotiable habit for many patients, some find building the injection into a weekend routine first, when there is no commute or school run adding pressure, helps them settle into the rhythm.

Who the evidence supports, and what a prescriber looks at

Wegovy is licensed for adults with a BMI of 30 or above, or 27 to 29.9 with at least one weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea or prediabetes. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. BMI alone does not determine suitability: a prescriber also considers medical history, current medications and any contraindications before treatment is appropriate.

Semaglutide is not recommended during pregnancy, for people trying to conceive, or while breastfeeding. It is not licensed for under-18s. People with a history of pancreatitis or certain gastrointestinal conditions need to discuss this with a clinician before starting.

NICE recommends semaglutide (TA875) for use within a specialist weight management service for a maximum of two years; private treatment operates under the licensed prescribing criteria. If you are exploring whether treatment is right for you, our weight-loss treatment overview sets out the options clearly, and our clinical team includes GPhC-registered independent prescribers who review every consultation personally. A contextual note: if you are also taking dulaglutide and want to understand whether combining the two is safe, our page on whether you can take Trulicity and Wegovy together addresses that question directly, and for broader outcome comparisons the Wegovy page covers those in more depth.

If the evidence here matches what you have been reading and you want to know whether semaglutide is clinically suitable for you, start your free consultation with our prescribers.