Each trajectory models the S-curve weight loss pattern observed in trials:
- Median trajectory: Based on the published mean weight loss percentage at trial endpoint, using an S-curve interpolation over the reported trial duration.
- Optimistic (top 25% responder): In SURMOUNT-1, the top quartile lost approximately 30–35% body weight at 15 mg tirzepatide; for semaglutide approximately 20–22%. The optimistic trajectory applies a 1.35× multiplier to the median.
- Conservative (bottom 25% responder): The bottom quartile of responders lost approximately 5–8% across medications. The conservative trajectory applies a 0.65× multiplier to the median.
If your goal percentage exceeds the medication's efficacy ceiling, the calculator will flag this. Reaching your goal may require lifestyle changes, medication escalation, or switching medications — discuss with your prescriber.