GLP-1 Weight Loss Projection Calculator
See your projected weight loss based on STEP-1 and SURMOUNT-1 clinical trial data.
How This Calculator Works
This calculator uses data from the STEP-1 trial (semaglutide, NEJM 2021 — 14.9% mean loss over 68 weeks) and SURMOUNT-1 trial (tirzepatide, NEJM 2022 — up to 22.5% over 72 weeks). A non-linear curve reflects real-world patterns: months 1-3 account for ~40% of total loss, months 4-6 add 30%, months 7-9 add 20%, months 10-12 add the final ~10%. The lifestyle multiplier (0.85x, 1.0x, or 1.2x) adjusts for your level of dietary and exercise commitment alongside medication.
Expected Weight Loss by Medication
Wegovy (semaglutide 2.4mg): 14.9% over 68 weeks, STEP-1 trial. Ozempic (semaglutide 1mg): ~6% over 52 weeks, SUSTAIN. Zepbound (tirzepatide 15mg): 22.5% over 72 weeks, SURMOUNT-1. Mounjaro (tirzepatide 15mg): ~19.5% over 72 weeks, SURMOUNT-2. Compounded semaglutide: ~13% estimated. Compounded tirzepatide: ~20% estimated. These are population averages — individual responses range widely.
Month-by-Month: What Weight Loss Actually Looks Like
Most GLP-1 users experience rapid initial response in months 1-3 as appetite suppression takes effect. This is when roughly 40% of total projected loss typically occurs. Months 4-6 add approximately 30%, months 7-9 add 20%, and the final phase contributes the rest. This slowing is normal physiology, not medication failure — the body adapts to a new set point. Patients who maintain medication and lifestyle changes typically sustain most of their loss long-term.
Factors That Affect Your Results
- Starting weight — higher baseline often correlates with larger absolute losses
- Dose adherence — consistent weekly injections and proper titration matter significantly
- Diet quality — GLP-1 reduces appetite but nutritional awareness remains important
- Exercise — resistance training preserves muscle; cardio accelerates fat loss
- Sleep quality — poor sleep elevates hunger hormones, counteracting GLP-1 effects
- Underlying conditions — hypothyroidism, PCOS can slow weight loss response
- Individual genetics — some people are higher or lower responders to GLP-1 agonists
Semaglutide vs Tirzepatide: Which Produces More Weight Loss?
Tirzepatide consistently outperforms semaglutide in head-to-head data. As a dual GIP/GLP-1 agonist, tirzepatide produced 22.5% average body weight loss in SURMOUNT-1 vs Wegovy's 14.9% in STEP-1 — roughly 50% more effective. However, semaglutide has a longer track record, may be better tolerated by some patients, and is often cheaper (especially compounded). Your provider can help choose based on your health history, budget, and goals.
Frequently Asked Questions
Will I regain weight when I stop GLP-1?
Most research shows significant weight regain within 1-2 years of stopping. These medications are often considered long-term or indefinite treatment, similar to blood pressure or cholesterol medications.
Why does my result differ from what my doctor said?
This tool uses population averages. Your provider factors in your specific health history, starting weight, and other individual variables.
Is 22% weight loss with tirzepatide realistic for me?
It is possible but not guaranteed. 22.5% was the average at the highest tirzepatide dose over 72 weeks — about 1 in 3 participants lost 25% or more.
Does insurance cover Wegovy or Zepbound for weight loss?
Coverage varies widely. Medicare does not cover GLP-1 for obesity. Commercial insurance coverage is improving but inconsistent. Check our Cost Calculator for personalized coverage info.
What if I can only afford a lower dose?
Lower doses still produce meaningful weight loss. Compounded GLP-1 at appropriate doses delivers clinical results at a fraction of brand-name costs.