How much weight can you lose on a GLP-1?
In the largest obesity trials, people lost about 15% of body weight on average with semaglutide and up to roughly 20% with tirzepatide, over 16–17 months alongside lifestyle support [1][2]. The calculator above places your own goal against those trial averages (the percentage loss it represents, and a realistic timeline) using the trial figures below, not round marketing numbers.
How much weight will I lose on semaglutide (Wegovy, Ozempic)?
On average, about 15% of body weight over roughly 16 months in the main obesity trial (STEP-1), which studied the higher-strength semaglutide sold for weight loss as Wegovy [1]. Ozempic is the same medicine, approved for type 2 diabetes rather than for weight loss. Results vary widely between individuals.
How much weight will I lose on tirzepatide (Mounjaro, Zepbound)?
On average, more than semaglutide: roughly 20% of body weight at the higher amounts by about 17 months in its obesity trial (SURMOUNT-1), with a range of roughly 15–21% [2]. Tirzepatide is the same medicine sold as Zepbound for weight loss and Mounjaro for type 2 diabetes; the average assumes continued treatment.
Do you keep the weight off?
Most loss happens in the first several months, then slows, so a smaller goal is reached sooner than a proportional share of a large one. But weight is commonly regained after stopping: in STEP-4, people who switched to placebo regained much of what they'd lost [3]. A GLP-1 works while it's taken; a durable result usually means ongoing treatment and lifestyle change together.
The honest bottom line
This is an educational estimate, not a prescription and not a promise. Whether a GLP-1 is right for you (and which one) is a clinical decision based on your health, not a calculator. If you're considering treatment, the useful next step is a conversation with a clinician.
References
[1] Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989-1002. doi:10.1056/nejmoa2032183 https://pubmed.ncbi.nlm.nih.gov/33567185/
[2] Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216. doi:10.1056/nejmoa2206038 https://pubmed.ncbi.nlm.nih.gov/35658024/
[3] Rubino D, Abrahamsson N, Davies M, et al. Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA. 2021;325(14):1414-1425. doi:10.1001/jama.2021.3224 https://pubmed.ncbi.nlm.nih.gov/33755728/