GLP-1 weight loss: what the trials found

What this tool shows

This tool applies the average result published by the clinical trial behind each medication (STEP 1, SURMOUNT-1, SCALE, SUSTAIN 7 and LEAD-6) to your current weight. The tool uses only each trial’s published end point as data, together with who the trial studied and, where the trial reported it, how many people given the medication reached 5%, 10% or more. SUSTAIN 7 (Ozempic) and LEAD-6 (Victoza) studied adults with type 2 diabetes against another diabetes medicine, with no placebo; STEP 1 (Wegovy), SURMOUNT-1 (Mounjaro, Zepbound) and SCALE (Saxenda) studied adults with obesity or overweight without diabetes, against placebo, with lifestyle counselling in both groups.

Who is this for?

GLP-1 users at any stage who want a realistic reference point. A trial average is a group figure from a supervised study, not a target: some participants lost much more and some much less, and the placebo groups lost weight too. Use it as context for a conversation with your prescriber.

Frequently asked questions

How much weight can you lose on Ozempic?

Ozempic is a type 2 diabetes medicine. In SUSTAIN 7 (Pratley et al., Lancet Diabetes Endocrinol 2018), a 40-week trial in adults with type 2 diabetes compared with dulaglutide, people on Ozempic 1.0 mg lost 6.5 kg on average while they stayed on treatment. Wegovy is a separate semaglutide medicine prescribed for weight management: in STEP 1 (Wilding et al., NEJM 2021), a placebo-controlled trial in adults without diabetes, it averaged 14.9% at 68 weeks, against 2.4% on placebo. The two trials studied different people and cannot be compared directly. Individual results vary widely, and any question about your dose is one to talk through with your prescriber.

Is Mounjaro better than Ozempic for weight loss?

Results from separate trials cannot be compared directly. One trial compared the two molecules head to head: in SURMOUNT-5 (Aronne et al., NEJM 2025; adults with obesity, without diabetes), tirzepatide (Mounjaro/Zepbound) at up to 15 mg averaged 20.2% weight loss at 72 weeks, against 13.7% for semaglutide at up to 2.4 mg, the Wegovy dose, which is higher than Ozempic doses. Individual response varies, and which medicine suits you is a decision for you and your prescriber.

Why am I losing weight slower than the trial average?

Slower than the average is common. An average sits in the middle of a wide spread: in STEP 1 (Wilding et al., NEJM 2021), among people given semaglutide 2.4 mg who had a week-68 weight, 13.6% lost less than 5% of their weight, while about half lost 15% or more. Trial participants were in supervised studies, with regular lifestyle counselling in the obesity trials. Dose changes, side effects, plateaus and stress also shape real-world results. If your progress worries you, talk it through with your prescriber.

Will I keep the weight off?

In the STEP 1 extension (Wilding et al., Diabetes Obes Metab 2022), people who stopped semaglutide 2.4 mg and the trial’s lifestyle programme regained, on average, about two-thirds of the weight they had lost within a year. If you are thinking about stopping or changing your medication, plan it with your prescriber.