GLP-1 Weight Loss Projection Calculator
Estimate expected weight loss on a GLP-1 weight-loss medication based on the published clinical trial that established its efficacy. Adjusts for BMI category based on subgroup data. Educational tool, not a substitute for individual medical advice.
- BMI
- 31.6 — Class 1 obesity
- Trial reference
- SURMOUNT-1 (NEJM 2022)
- Mean trial weight loss
- 20.9% at week 72
- Your BMI-adjusted projection
- ~20.9% (~46 lb)
Projected weight by week
| Week | % loss | Pounds lost | Projected weight |
|---|---|---|---|
| 4 | 1.2% | 2.6 | 217.4 lb |
| 8 | 2.3% | 5.1 | 214.9 lb |
| 12 | 3.5% | 7.7 | 212.3 lb |
| 16 | 4.6% | 10.2 | 209.8 lb |
| 24 | 7.0% | 15.3 | 204.7 lb |
| 36 | 10.4% | 23.0 | 197.0 lb |
| 52 | 15.1% | 33.2 | 186.8 lb |
| 68 | 19.7% | 43.4 | 176.6 lb |
| 72 | 20.9% | 46.0 | 174.0 lb |
| 104 | 20.9% | 46.0 | 174.0 lb |
Educational projection only. Individual results vary substantially. Use with a licensed prescriber to determine medical eligibility, dose, and monitoring. Source: linked clinical trial above.
What this tool calculates
For each medication, the projection anchors to the mean weight loss observed in the pivotal randomized controlled trial at the trial-defined endpoint. For semaglutide 2.4 mg, that is 14.9% mean body-weight loss at week 68 in STEP-1 (Wilding et al., NEJM 2021). For tirzepatide 15 mg, it is 20.9% mean loss at week 72 in SURMOUNT-1 (Jastreboff et al., NEJM 2022). A modest BMI-category factor is applied because higher starting BMI was associated with slightly larger relative weight loss in pre-specified subgroup analyses.
What this tool does not predict
Individual response is highly variable. Roughly one-third of patients in STEP-1 lost more than 20% body weight; another third lost between 5% and 10%; a minority lost less than 5%. Side-effect tolerance, dose escalation pace, adherence, and baseline metabolic profile all materially affect outcome. Discontinuation is followed by substantial weight regain (STEP-1 extension data: ~two-thirds of the loss regained within 1 year of stopping).
Methods note
The week-by-week projection assumes a linear ramp to the trial-defined peak. Real trial curves are slightly concave (faster early loss, plateau by month 9-12), but the linear approximation is well within the trial's reported variance for patient-level counseling purposes.
Last medically reviewed by the HealthRX Medical Team.