The trials give a fairly consistent answer: about 15% of body weight on the 2.4 mg dose, for adults with obesity and without diabetes, reached over a year or more. The spread around that average is wide, and people with diabetes lost less.
This page sets out what the semaglutide weight trials measured: the average, the spread, the effect of diabetes and dose, and how long the loss lasted.
What STEP 1 measured
STEP 1 randomized 1,961 adults with a BMI of 30 or more, or 27 or more with a weight-related condition [2]. People with diabetes were excluded. Two in three got semaglutide 2.4 mg once weekly and one in three got placebo, for 68 weeks, with lifestyle counseling for everyone.
−14.9%
Mean weight change on 2.4 mg at week 68
Wilding 2021
−2.4%
Mean weight change on placebo
Wilding 2021
−15.3 kg
Mean change on 2.4 mg, against −2.6 kg on placebo
Wilding 2021
The 15.3 kg average is about 34 pounds. That conversion is plain arithmetic on the trial’s own figure, not a number the trial reported in pounds.
The analysis counted everyone assigned to the drug, including people who stopped taking it. So the average includes some who were no longer on treatment by week 68.
How the results were spread
A single mean says little about one person. STEP 1 also reported the share of each group that crossed each threshold at week 68 [2].
| Weight lost | Placebo | Semaglutide 2.4 mg |
|---|---|---|
| 5% or more | 31.5% | 86.4% |
| 10% or more | 12.0% | 69.1% |
| 15% or more | 4.9% | 50.5% |
Read the other way, about 14% of the semaglutide group did not reach a 5% loss. About half did not reach 15%. Gastrointestinal effects led 4.5% on semaglutide to stop treatment, against 0.8% on placebo.
The full side-effect record is in semaglutide side effects.
With type 2 diabetes
STEP 2 enrolled 1,210 adults with type 2 diabetes and a BMI of 27 or more [3]. After 68 weeks, weight fell 9.6% on 2.4 mg and 3.4% on placebo.
That is a real loss, but about 5 points less than in STEP 1. The same gap between people with and without diabetes appears in the tirzepatide trials, set out in how much weight you can lose on tirzepatide.
How fast it comes off
The label starts at 0.25 mg weekly and steps up every 4 weeks, reaching 2.4 mg at week 17 [1]. Much of the first four months is spent on doses below the one the trials tested for weight.
The dose steps are covered in semaglutide dosage, and the early weeks in how long semaglutide takes to work.
Two years and four years
STEP 5 ran for 104 weeks in 304 adults without diabetes [4]. Weight fell 15.2% on 2.4 mg and 2.6% on placebo, and 77.1% on semaglutide kept at least a 5% loss at two years.
The SELECT trial followed 17,604 adults with heart disease and overweight or obesity, without diabetes [5]. Its weight analysis found the loss continued for 65 weeks and held to week 208.
At 208 weeks the mean change was 10.2% on semaglutide and 1.5% on placebo. SELECT was a heart-outcomes trial in an older, higher-risk group, so its weight figure is not directly comparable with STEP 1.
What the 7.2 mg dose added
The label now allows 7.2 mg weekly for adults who have tolerated 2.4 mg for at least 4 weeks and need more weight reduction [1]. STEP UP tested it in 1,407 adults with obesity and without diabetes [6].
At 72 weeks, mean weight change was 18.7% on 7.2 mg, 15.6% on 2.4 mg and 3.9% on placebo. The extra 3.1 points came with more side effects.
Gastrointestinal effects were reported by 70.8% on 7.2 mg and 61.2% on 2.4 mg. Dysesthesia, an altered or painful skin sensation, affected 22.9% on 7.2 mg against 6.0% on 2.4 mg.
Stopping is covered in more depth in what happens when you stop taking semaglutide.
What these numbers do not tell you
Every trial here used the brand injection alongside diet and activity counseling. Most participants were women: 77.6% in STEP 5 and 73.7% in STEP UP [4] [6].
No trial here tested compounded semaglutide, so these figures say nothing either way about it. The daily alternative produced smaller losses, as set out in liraglutide dosage. For eating on the drug, see what to eat on semaglutide.
The tablet form has its own trial record, covered in Wegovy pill. To compare online prescribers, see the compounded semaglutide rankings and the broader weight-loss peptide rankings.