In the two big obesity trials, the average person on semaglutide (the Wegovy trial) lost 14.9% of their body weight by week 68, against 2.4% on placebo.1 On tirzepatide (Zepbound's molecule) the averages at week 72 were 15.0%, 19.5% and 20.9% across the three doses tested, from lowest to highest, against 3.1% on placebo.3 On a 230 lb starting weight that is the difference between about 34 lb and a few lb; the trials report percentages, so the arithmetic is yours to do.
We use no patient photos on purpose. A before-and-after photo is the result someone chose to share, and a photo cannot show the part that matters most: how far the group spread around the average. The trials report everyone who was enrolled, so this page uses their numbers, by timepoint.
The after, by timepoint
The two pivotal trials only report the end of the study. The earlier points come from smaller or non-randomized studies, so read the rows above week 68 as a rough shape, not a forecast.
| When | Who and what | Average weight loss |
|---|---|---|
| Week 12 | 30 adults with obesity, semaglutide, 12-week crossover trial8 | 5.0 kg, "predominantly from body fat mass" |
| Month 3 | Mayo Clinic routine-care cohort, semaglutide6 | 5.9% |
| Week 20 | 72 adults with obesity, semaglutide7 | 9.9% vs 0.4% on placebo |
| Month 6 | Same Mayo Clinic cohort6 | 10.9% |
| Week 68 | STEP 1, 1,961 adults without diabetes, semaglutide12 | 14.9% vs 2.4% on placebo |
| Week 72 | SURMOUNT-1, 2,539 adults without diabetes, tirzepatide34 | 15.0%, 19.5% and 20.9% across the three doses tested vs 3.1% on placebo |
Two things shape the early rows. Both brands start low and step up, so the first weeks are on starter doses; in the trials it took 16 weeks to reach the full dose of semaglutide2 and 20 weeks for tirzepatide.4 And the Mayo rows are routine care, with no placebo group. For the first six weeks on one drug, see Ozempic 6 week results, and for how the clocks work see how long GLP-1s take to work.
The spread: not everyone is the average
An average of 15% sounds like a promise. The share-of-people numbers show what it is made of.
| Trial and arm | Lost at least 5% | At least 10% | At least 15% | At least 20% |
|---|---|---|---|---|
| STEP 1, semaglutide1 | 86.4% | 69.1% | 50.5% | not in the abstract |
| STEP 1, placebo1 | 31.5% | 12.0% | 4.9% | not in the abstract |
| SURMOUNT-1, tirzepatide, lowest dose tested3 | 85% | not in the abstract | not in the abstract | not in the abstract |
| SURMOUNT-1, tirzepatide, middle dose3 | 89% | not in the abstract | not in the abstract | 50% |
| SURMOUNT-1, tirzepatide, highest dose tested3 | 91% | not in the abstract | not in the abstract | 57% |
| SURMOUNT-1, placebo3 | 35% | not in the abstract | not in the abstract | 3% |
Read it this way: on semaglutide, about half of the group passed 15% and about one in seven (100% minus 86.4%) did not reach 5%.1 On tirzepatide at the top dose, more than half passed 20%.3 Those are people who stayed in the analysis regardless of whether they kept taking the drug, which is how the trials count them, so the figures include people who stopped early.13
If you have type 2 diabetes
The same drugs lose less weight in people with diabetes. In SURMOUNT-2, the 72-week tirzepatide trial in adults with obesity and type 2 diabetes, the averages were 12.8% and 14.7% on the two doses tested, against 3.2% on placebo.5 The same pattern showed at three months in the Mayo cohort: 3.9% with diabetes against 6.3% without.6 A diabetes result is not a failed result; it is a different curve.
The after is not permanent
The STEP 1 team followed 327 people for a year after treatment ended. They had lost 17.3% on average by week 68 in that subset, and by week 120 they had regained 11.6 percentage points of it, leaving a net loss of 5.6%.9 The authors summarise it as "participants regained two-thirds of their prior weight loss".9 That is the main reason the cost per month matters: the trials describe a drug you keep taking. More in stopping a GLP-1 and weight regain.
What is not in a before-and-after photo
- Which dose and which week. A photo at month 14 on a top dose is not a month-3 result on a starter dose.
- Lean mass. Weight lost is not all fat; the 12-week trial reports the loss "predominantly from body fat mass", and GLP-1 muscle loss covers the rest.
- The face. Quick loss changes it; see Ozempic face.
- Lifestyle support. Every trial above paired the drug with lifestyle intervention,2 so the placebo arm lost weight too.
What it costs to get there
The trial arms ran for about 16 to 17 months, so a realistic budget is the monthly price times the months you stay on. On our board today the cheapest cash GLP-1 program is $41 a month, the middle of the board is $134, and the most expensive is $299. A licensed clinician decides whether you qualify, and compounded versions are not FDA approved.
Brand-name tirzepatide and semaglutide cost more than most compounded programs and are covered by some insurance. See cheapest tirzepatide, cheapest semaglutide and tirzepatide vs semaglutide for the two molecules side by side.