Setting a goal that matches the drug
The single biggest source of disappointment on GLP-1 therapy is a goal that exceeds the drug’s trial-validated ceiling. Semaglutide 2.4mg averages 14.9% total body-weight loss (TBWL) at 68 weeks in STEP 1. Tirzepatide 15mg averages 22.5% TBWL at 72 weeks in SURMOUNT-1. If your goal requires 28% loss, you’re planning past the top-line trial outcome of the best available monotherapy. That doesn’t mean it’s impossible — about 10–15% of patients in SURMOUNT-1 lost 25%+ — but it should be the start of a conversation about combination therapy, bariatric surgery consideration, or a recalibrated number.
The calculator above translates your chosen drug and starting weight into a realistic timeline. Cross-check against SURMOUNT-5 head-to-head data if you’re choosing between semaglutide and tirzepatide for weight-loss purposes specifically.
The three phases of a GLP-1 weight-loss curve
- Weeks 0–12 (titration): 2–6% TBWL. You’re still climbing to therapeutic dose. Most of this phase is appetite suppression just starting to show up. Water-weight drops of 3–6 lb in the first 2 weeks are common.
- Weeks 12–32 (steepest phase): 0.5–1.0% TBWL per week. Therapeutic dose achieved, appetite suppression compounds with a calorie deficit you probably didn’t have to enforce consciously. This is where most of the absolute weight comes off.
- Weeks 32–72 (glidepath): 0.2–0.4% TBWL per week, tapering to near-zero. Your body is finding a new set point. Loss slows. This is not a failure — this is the expected shape of the curve.
Why you need a tracker, not just a calculator
Trial averages are averages. Your individual trajectory will deviate — sometimes meaningfully. Some patients run 30% ahead of average (super-responders); about 10–15% run 50% behind average or fail to hit 5% TBWL (non-responders). You need real data on your own response to know which category you’re in.
A minimum viable progress log: one entry per week, ideally same day, same time, same clothes. Waist circumference monthly is a useful parallel metric — it often moves even when the scale doesn’t, because you’re losing visceral fat and gaining muscle. The tracker above handles both.
Tips for realistic milestones
- Month 1 (end of first titration):2–4% TBWL on either drug. Don’t panic if it’s 1.5%.
- Month 3 (90 days):5–7% on semaglutide, 6–9% on tirzepatide. This is the FDA’s “clinically meaningful response” threshold.
- Month 6: 9–12% semaglutide, 13–17% tirzepatide. This is often when BMI crosses a payer threshold.
- Month 12: 13–16% semaglutide, 18–22% tirzepatide. Most patients are at or approaching goal.
- Month 18+: Maintenance. Weight stabilizes. Focus shifts to protein, resistance training, and keeping the habits built during loss.