Weight loss medications compared
This page has not yet been reviewed by a credentialed medical professional. It is educational and is not medical advice.
What each approved option achieved in its main phase 3 trial, with the placebo result alongside. Every number links to the PubMed record.
| Medication | Form | Best-dose avg. loss | Placebo | Trial |
|---|---|---|---|---|
| Tirzepatide Zepbound (weight), Mounjaro (diabetes) | weekly injection | -20.9% (15 mg) | -3.1% | SURMOUNT-1 n=2,539, 72 wk, Eli Lilly |
| Semaglutide injection Wegovy (weight), Ozempic (diabetes) | weekly injection | -14.9% (2.4 mg) | -2.4% | STEP 1 n=1,961, 68 wk, Novo Nordisk |
| Semaglutide pill Wegovy pill | daily pill | -13.6% (25 mg) | -2.2% | OASIS 4 n=307, 64 wk, Novo Nordisk |
| Orforglipron Foundayo | daily pill | -11.2% (36 mg) | -2.1% | ATTAIN-1 n=3,127, 72 wk, Eli Lilly |
| Liraglutide Saxenda (weight), Victoza (diabetes) | daily injection | Mean loss 8.4 kg vs 2.8 kg on placebo at 56 weeks (63.2% vs 27.1% lost at least 5%). | see note | SCALE Obesity and Prediabetes n=3,731, 56 wk, Novo Nordisk |
| Phentermine / topiramate Qsymia | daily pill | -9.8% (15 mg / 92 mg) | -1.2% | CONQUER n=2,487, 56 wk, not stated in abstract |
Percent change in body weight from baseline at the end of each trial. Trials differ in population, duration and analysis method, so do not compare rows directly. Direct head-to-head results are below.
Head-to-head trials
- Tirzepatide vs semaglutide (SURMOUNT-5): -20.2% vs -13.7% at 72 weeks (open-label, n=751)
- Semaglutide vs liraglutide (STEP 8): -15.8% vs -6.4% at 68 weeks (open-label, n=338)
What the numbers do and do not mean
- Averages hide a wide range. Some people lose far more than the average and some lose little.
- Placebo groups also got lifestyle support and still lost 1% to 3% on average.
- The effect depends on continuing treatment. After stopping, much of the weight returns.
- Side effects are mostly gastrointestinal (nausea, vomiting, diarrhea, constipation), usually during dose escalation.
- Most pivotal trials were funded by the manufacturer.
Individual options
Tirzepatide (Zepbound (weight), Mounjaro (diabetes))
Highest average weight loss of any approved option. In the SURMOUNT-5 head-to-head it beat semaglutide (-20.2% vs -13.7% at 72 weeks).
US status: FDA-approved prescription drug.
Semaglutide injection (Wegovy (weight), Ozempic (diabetes))
Also reduced major cardiovascular events in people with heart disease and overweight (SELECT). In the STEP 1 extension, people regained about two-thirds of the weight within a year of stopping.
US status: FDA-approved prescription drug.
Semaglutide pill (Wegovy pill)
Taken on an empty stomach with a small sip of water, with a wait before eating. Gastrointestinal events were more common than placebo (74.0% vs 42.2%). A smaller trial than the injectables.
US status: FDA-approved for chronic weight management (December 2025), per news reports and company statements; check the FDA label.
Orforglipron (Foundayo)
A small-molecule (non-peptide) pill. Discontinuation due to adverse events was 5.3 to 10.3% across doses vs 2.7% on placebo.
US status: FDA-approved (April 2026), per news reports and company statements; check the FDA label. Not a peptide drug.
Liraglutide (Saxenda (weight), Victoza (diabetes))
An earlier daily GLP-1 drug. In the STEP 8 head-to-head, weekly semaglutide produced more weight loss than liraglutide (-15.8% vs -6.4% at 68 weeks).
US status: FDA-approved prescription drug.
Phentermine / topiramate (Qsymia)
An older oral option that is not a peptide drug. Prescribing information carries important cautions (for example, pregnancy risk with topiramate); read the full label.
US status: FDA-approved prescription drug. Not a peptide drug.
Frequently asked questions
Which weight loss medication works best?
In the one direct head-to-head obesity trial, tirzepatide produced more average weight loss than semaglutide (-20.2% vs -13.7% at 72 weeks). Individual results vary widely, and tolerability, cost and medical history matter.
How much weight do people lose on weight loss medication?
Placebo-controlled phase 3 trials report average losses of roughly 8% to 21% of body weight over 56 to 72 weeks, compared with about 1% to 3% on placebo with lifestyle support. These are averages, not predictions.
What happens when you stop?
In the STEP 1 extension, people who stopped semaglutide regained about two-thirds of their lost weight within a year. In SURMOUNT-4, people who switched from tirzepatide to placebo regained much of it.
Who qualifies for these medications?
The trials enrolled adults with BMI of 30 or more, or 27 or more with a weight-related condition. Actual prescribing criteria are set by each drug's label and your clinician.
Related
Educational only, not medical advice. Weight loss medication has risks and is prescribed by a clinician.