Wegovy results: the week-by-week STEP-1 milestones you should actually expect

What STEP-1 actually measured — read this first

STEP-1 is the pivotal Wegovy weight-loss trial: 1961 adults with BMI ≥30 (or BMI ≥27 plus a weight-related comorbidity), randomized 2:1 to semaglutide 2.4 mg once weekly vs placebo, both arms with lifestyle intervention. Duration: 68 weeks (16-week dose escalation + 52-week maintenance). Published in NEJM in March 2021 (Wilding et al.).

Every weekly milestone below is either from the primary STEP-1 report or the pre-planned analysis figures — no extrapolation, no marketing gloss. If the trial did not report a specific week, this guide says so.

This is not medical advice for your individual case. It is what the trial cohort experienced, on average, at each dose step. Your rate depends on starting weight, protein target, sleep, strength training, and adherence. Talk to your prescriber for individual dose decisions.

• Sources for this section
• Wilding JPH et al. — Once-Weekly Semaglutide in Adults with Overweight or Obesity — New England Journal of Medicine, 384:989-1002, 2021
• Wegovy FDA prescribing information (2024 revision) — US FDA

Weeks 0-4: 0.25 mg — the tolerability starter

You start Wegovy at 0.25 mg once weekly. This is a subtherapeutic dose: it does not by itself drive meaningful weight loss. Its job is to test your GI tolerance and buy 4 weeks of adaptation before the first real dose step.

Expected loss by week 4: STEP-1 showed roughly −1 to −2% of starting body weight (about 2-5 lbs for a 200-lb starting weight, mostly water). If you weigh yourself daily and expect big drops, you will be disappointed. This is by design.

Common side effects in this window: mild nausea after injection (~20% of STEP-1 patients), occasional loose stool or constipation (~15%), reduced appetite (which most patients notice as "food noise" quieting rather than hunger loss). If these are severe now, they will get worse at the 0.5-1.0 mg steps — call your prescriber to slow titration.

Weeks 4-8: 0.5 mg — the first real step

At week 4 your dose steps to 0.5 mg. Appetite suppression becomes more noticeable. Portions naturally shrink. Many patients describe forgetting to eat lunch.

Expected loss by week 8: STEP-1 mean ~3-4% of starting body weight. Nausea and other GI symptoms often peak transiently for 24-48 hours after each dose step and then subside within a week.

Common mistake in this window: eating too little because appetite drops. Under 1200 kcal/day and under 0.7 g protein per lb body weight both accelerate muscle loss. Set a protein floor and hit it even if you are not hungry.

Weeks 8-12: 1.0 mg — where side effects usually peak

The 1.0 mg step (weeks 8-12) is the roughest window for most patients. STEP-1 reported the highest incidence of nausea, vomiting, and diarrhea during this titration step. If your worst week is week 9 or 10, you are on the standard curve.

Expected loss by week 12: STEP-1 mean ~5-6%. This is when clothing changes become noticeable and the trajectory feels real.

Practical guidance for the 1.0 mg step: smaller meals more often, no fried food, no alcohol on injection day, hydrate aggressively. If nausea is preventing food intake for more than 3 days, call your prescriber — a delayed step to 1.7 mg is often the right call, not pushing through.

Weeks 12-16: 1.7 mg — the sub-maintenance step

Week 12-16 is the final titration step before reaching maintenance. GI side effects usually decline vs the 1.0 mg step — the body adapts.

Expected loss by week 16: STEP-1 mean ~7-8%. For patients in the fastest quartile: ~10-11%.

This is when many patients are tempted to skip a dose or stretch a week because side effects seem manageable and cost pressure is real. Do not. STEP-1 patients who adhered week-over-week hit the trial mean. Non-adherers regressed toward placebo (−2.4%) proportionally.

Weeks 16-20: 2.4 mg — the maintenance dose starts

Week 16 you reach the STEP-1 maintenance dose (2.4 mg) and stay there through the remaining 52 weeks. GI side effects usually stabilize or decline within 2-3 weeks of this step. Nausea beyond week 20 is unusual — flag it to your prescriber.

Expected loss by week 20: STEP-1 mean ~7-9%. The maintenance-dose curve is where the trial mean pulls away from placebo most rapidly.

Weeks 20-44: the fastest loss window

STEP-1 patients accumulated most of their total loss between weeks 20 and 44 (24 weeks at maintenance dose). The curve shape is roughly linear during this window, ~0.25-0.35% of starting body weight per week.

Expected loss by week 32: STEP-1 mean ~11-12%. By week 44: ~13-14%.

Plateau windows within this stretch (2-4 weeks where the scale stalls) are common and expected — they resolved without dose changes in the trial cohort. Common triggers: protein below 0.7 g/lb, sleep under 7 hrs, unusual stress, or a menstrual-cycle water fluctuation. Not a sign to escalate dose or switch drugs.

Hair shedding often begins between week 12 and week 24 — telogen effluvium is a stress response to rapid weight loss, not a drug toxicity. It fully reverses within 6-9 months once weight stabilizes if protein and ferritin are adequate.

Weeks 44-68: the plateau tail

The last ~24 weeks of STEP-1 added roughly 1-2 percentage points on top of the week-44 loss — the curve is flatter here. Mean at week 68 = −14.9%. About one-third of patients reached ≥20% loss; half reached ≥15%.

This is when patients start asking "am I done losing?" The trial answer: possibly. Continued loss beyond week 68 has been observed in extension studies (SELECT trial), but the rate slows further. If you are at a healthy BMI and body composition, this is maintenance, not failure.

Discontinuing at this point leads to substantial regain — the STEP-4 trial (Rubino et al., JAMA 2021) showed patients who switched to placebo at week 20 regained roughly two-thirds of their loss over the following 48 weeks. See our companion guide on preventing rebound weight gain.

• Sources for this section
• Rubino D et al. — Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss (STEP-4) — JAMA, 325(14):1414-1425, 2021

Your realistic band — not the mean

Trial means hide huge individual variation. STEP-1 published response quartiles: 86% of the semaglutide arm hit ≥5% loss, 69% hit ≥10%, 51% hit ≥15%, 32% hit ≥20%. Roughly 12% did not respond meaningfully. These bands, not the mean, are what you should expect.

What predicts being in the higher quartile: (a) starting protein at 0.7-1.0 g per lb goal weight, (b) two strength-training sessions per week from month 2 onward, (c) adherence — hitting your weekly dose within the on-label 48-hour window, (d) sleep at 7+ hours. What predicts the lower quartile: none of the above, plus stress-eating on nauseous days.

If at week 20 you are at less than 5% of starting weight lost, you are in the low-response tail. Options: extend to the STEP-5 protocol (continue past 68 weeks), switch to Zepbound (tirzepatide), or reassess for undiagnosed hypothyroidism / sleep apnea / cortisol drivers.