GLP-1 results vary widely. In trials, most people reached at least 5 percent weight loss while a minority did not. Medication and dose, type 2 diabetes, staying on treatment and early response all help explain the spread.
People respond very differently to GLP-1 medications, and that is visible in every major trial. In the STEP 1 trial of semaglutide, about half of participants lost 15 percent or more of their body weight, while roughly 1 in 7 did not reach 5 percent. The research points to several reasons for the spread: which medication and dose someone takes, whether they have type 2 diabetes, how consistently they stay on treatment, and how their body responds in the first months. Knowing these factors can help you set realistic expectations and have a more useful conversation with your prescriber.
Average results get the headlines, but the distribution tells a more useful story. In STEP 1, published in the New England Journal of Medicine in 2021, 1,961 adults without diabetes were randomized to semaglutide or placebo for 68 weeks, both with lifestyle support. The average change in body weight was a 14.9 percent reduction with semaglutide versus 2.4 percent with placebo. Here is how participants were distributed:
| Weight reduction at 68 weeks | Semaglutide | Placebo |
|---|---|---|
| 5% or more | 86.4% | 31.5% |
| 10% or more | 69.1% | 12.0% |
| 15% or more | 50.5% | 4.9% |
The tirzepatide label reports a similar picture for SURMOUNT-1 at 72 weeks. At the highest dose, 90.9 percent of participants reached at least 5 percent weight reduction and 56.7 percent reached at least 20 percent; at the lowest dose, 30.0 percent reached 20 percent. With placebo, 34.5 percent reached 5 percent and 3.1 percent reached 20 percent.
In other words, a sizable group responded much more than average, most people landed in the middle, and a smaller group responded modestly. These figures come from controlled trials, and individual results vary.
Trials consistently show a dose relationship. In SURMOUNT-1, average weight change at 72 weeks was 15.0 percent with the 5 mg dose, 19.5 percent with 10 mg and 20.9 percent with 15 mg, compared with 3.1 percent with placebo.
A 2025 real-world study in the journal Obesity, which followed 7,881 adults in a large health system in Ohio and Florida, found the same pattern outside of trials. Higher maintenance dosages were associated with greater odds of reaching 10 percent weight loss, and tirzepatide was associated with greater odds than semaglutide. Notably, 80.8 percent of people in that study were on lower maintenance dosages, which the authors identified as one reason real-world results fell short of trial results.
This does not mean the highest dose is right for everyone. Dosing is set by the prescriber, who weighs your response against side effects and your health history. Our semaglutide vs. tirzepatide guide compares the two medications in more detail.
People with type 2 diabetes tend to lose less weight on the same medication. In the STEP 2 trial, published in The Lancet in 2021, adults with overweight or obesity and type 2 diabetes who received the same semaglutide dose used in STEP 1 lost an average of 9.6 percent of body weight at 68 weeks, compared with 3.4 percent with placebo. That is a meaningful benefit, but smaller than the 14.9 percent average in STEP 1, which excluded people with diabetes. If you have type 2 diabetes, comparing yourself with the STEP 1 or SURMOUNT-1 averages may set an unrealistic bar.
Consistency turned out to be one of the biggest factors in the real-world study. Average weight reduction at 1 year was:
| Treatment pattern | Average weight reduction at 1 year |
|---|---|
| Stopped within 3 months | 3.6% |
| Stopped between 3 and 12 months | 6.8% |
| Stayed on treatment | 11.9% |
Among people who stayed on treatment at higher maintenance dosages, average reduction was 13.7 percent with semaglutide and 18.0 percent with tirzepatide. People who did not stop had more than four times the odds of reaching 10 percent weight loss compared with those who stopped early. The authors concluded that higher discontinuation and lower maintenance dosages likely explain why real-world results were smaller than in the phase 3 trials.
The same study found women had higher odds than men of reaching 10 percent weight loss, another reminder that individual characteristics shape the response.
Many people wonder whether a slow start means the medication will not work. A post hoc analysis of the STEP 4 trial looked at exactly this question. Participants who had lost at least 5 percent by week 20 (88.0 percent of those randomized to continue semaglutide) went on to an average reduction of 19.7 percent by week 68. Those who had not reached 5 percent by week 20 still averaged a 6.4 percent reduction by week 68 if they continued semaglutide, compared with 0.3 percent if they switched to placebo.
The authors found that an early response strongly predicted reaching at least 5 percent weight loss later, while a slow start had limited predictive value. A slow first few months is worth discussing, but it is not necessarily a verdict.
Some contributors are outside the scope of these trials but still worth considering with your provider:
Headline trial results such as STEP 1 and SURMOUNT-1 come from participants without diabetes who received the studied doses along with lifestyle support. A large real-world study found average weight reduction at 1 year of 8.7 percent, lower than in trials, mainly because of stopping treatment and lower maintenance dosages. Your own result depends on many factors, and your prescriber can help you interpret it.
Not necessarily. In a STEP 4 analysis, people who had not reached 5 percent weight loss by week 20 still averaged a 6.4 percent reduction by week 68 when they continued semaglutide. Early response is a useful signal, but a slow start had limited value for predicting the final result.
On average, tirzepatide has produced larger weight reductions in trials and was associated with greater odds of 10 percent weight loss in the real-world study. Averages do not predict which medication will work best for you, and side effects, health history and access matter too. A prescriber can help you weigh the options.
It is reasonable to discuss your progress, since trials show results are dose-related. But dosing is set by the prescriber, who balances benefit against side effects and safety. Never adjust your own dose, especially with compounded products, which are not FDA-approved and have been linked to dosing errors.
If your results differ from what you expected, share your timeline, any side effects, and how consistently you have been able to take the medication. A licensed provider can review whether the medication, dose, nutrition or activity plan needs adjusting. This article is educational and does not determine eligibility for any treatment.
Written by the NewDay Wellness editorial team from the sources above and checked against them before publication, and medically reviewed by Dr. Sean Arora and Dr. Shannon Arora of Arora Health & Aesthetics; see our editorial standards. This article is educational and does not diagnose conditions, establish eligibility for any medication, or replace care from a licensed provider. Compounded medications are not FDA-approved.
Every weight loss method eventually levels off. The physiology behind plateaus, why GLP-1 medications delay them, and how to tell a true plateau from ordinary fluctuation.
Read articleResistance training is the single most effective way to protect muscle and bone while losing weight. Here is what the guidelines recommend, what the research shows, and how to begin safely without a gym background.
Read articleLosing weight means losing some muscle along with fat. What the research says about how much, why it matters, and the two levers that protect lean mass: protein intake and resistance training.
Read article