STEP 1 Trial Semaglutide Results: The Initial Weight Loss Percentage Explained

What did participants lose in the first weeks, before reaching the maintenance dose?

This is a question our prescribers hear most weeks, and it's a fair one. The trial data reports outcomes at 68 weeks, so the published figures reflect the full treatment period rather than a snapshot after the first pen. Early weight loss while titrating through the lower doses tends to be modest, participants start at 0.25mg weekly, stepping up roughly every four weeks toward the 2.4mg maintenance dose. The body is adjusting, appetite begins to shift, but the bigger reductions typically build as the dose reaches its therapeutic level.

What that means practically: anyone comparing their own early numbers to the 15% trial average is measuring against the wrong point in time. The STEP 1 figure captures the whole 68-week arc. Some participants saw more than 15%; many saw less. Biology, how strictly the lifestyle component was followed, and how well each person tolerated the dose increases all played a role.

For a broader picture of how weight loss percentages accumulate over a Wegovy course, the Wegovy weight loss percentages page breaks this down further.

How do the STEP 1 figures compare to what was seen across the wider trial programme?

STEP 1 is one trial within a larger programme. The STEP trials each tested semaglutide 2.4mg in slightly different populations: people with obesity and no diabetes (STEP 1), people with type 2 diabetes (STEP 2), people with obesity using more intensive lifestyle support (STEP 3), and a longer maintenance study (STEP 4). Results shifted across populations, with the diabetes cohort showing smaller reductions and the intensive lifestyle group showing larger ones.

STEP 1 remains the most-cited because its population most closely matches the licensed indication, adults with obesity or overweight plus a weight-related condition, without diabetes. The semaglutide weight loss trial page covers the wider STEP programme in more depth, including what STEP 4's withdrawal data showed about sustaining results.

NICE's appraisal of semaglutide, published at NICE TA875, drew on this body of evidence when recommending semaglutide for use within specialist weight management services under specific criteria. Those criteria are narrower than the licensed eligibility, worth understanding if you're weighing NHS access against a private route.

What do the results mean for someone considering semaglutide now?

Trial averages describe populations, not individuals. A 15% average means some participants lost 8% and others lost 22%. Body composition, starting weight, adherence, and how the dose was tolerated all fed into where any one person landed. If you want to explore what the REDEFINE 1 trial showed about semaglutide weight loss percentages, that data offers a useful comparison point alongside the STEP programme figures. The lean mass data from semaglutide trials adds a further dimension: a portion of weight lost across GLP-1 trials included lean mass, which is why protein intake and resistance activity are emphasised alongside treatment.

Semaglutide is dispensed in the UK as Wegovy, a prescription-only medicine from Novo Nordisk. Private treatment through a regulated pharmacy is one route for people who don't meet NHS criteria or prefer not to wait. If you are considering using supplements alongside your treatment, our page on whether CBD can be taken with Wegovy covers what you need to know before combining the two. The semaglutide overview covers the UK licence, eligibility, and how the medicine works for readers who want the fuller picture before speaking to a prescriber.

No trial statistic is a personal prediction. If the evidence interests you and you want to understand whether semaglutide is suitable for you specifically, the right next step is a clinical conversation. Speak to our prescribers through a free consultation, every application is reviewed the same day by a GPhC-registered Independent Prescriber.