GLP-1 Weight Loss Calculator

The STEP-1 trial (NEJM 2021) showed an average weight loss of 14.9% of body weight at 68 weeks with Wegovy (semaglutide 2.4mg). For a 250 lb person, that's about 37 lbs. Results ranged widely — from roughly 8% to 21% — depending on individual factors. Peak loss typically occurs around 16–18 months, with slight weight regain if the drug is discontinued.

The SURMOUNT-1 trial (NEJM 2022) found average weight loss of 20.9% at 72 weeks with tirzepatide 15mg. For a 250 lb person, that's approximately 52 lbs average. High responders lost up to 26–27% of body weight. Tirzepatide activates both GIP and GLP-1 receptors, making it more potent than semaglutide-only drugs for most patients.

Most patients begin to notice weight loss within the first 4–8 weeks, though early results during dose titration are often modest. Significant weight loss typically accelerates after reaching the maintenance dose (around months 4–5 for Wegovy, month 5 for Zepbound). The rate of loss slows after 12–18 months as the body approaches a new set point.

Yes — clinical studies show that most patients regain significant weight after stopping GLP-1 medications. The STEP-4 trial found that patients who stopped Wegovy regained two-thirds of their lost weight within one year. GLP-1s are generally considered long-term or indefinite treatments for chronic weight management, similar to blood pressure medication.

Head-to-head trials (SURMOUNT-5) showed tirzepatide produces significantly more weight loss than semaglutide. Average weight loss was ~20% for tirzepatide vs ~15% for semaglutide. However, tirzepatide may have more GI side effects, and individual responses vary. Both are highly effective — tirzepatide simply has a higher ceiling in clinical trials.

Key factors include: starting weight (higher BMI often = more absolute weight loss), adherence to the titration schedule, diet quality (lower calorie and lower carb diets enhance results), physical activity level, age, sex (women often respond differently than men), genetic factors, and whether you have type 2 diabetes (T2D patients sometimes lose slightly less). Our calculator uses trial averages as a baseline estimate.

Saxenda (liraglutide 3mg, daily injection) is effective but produces less weight loss than Wegovy or Zepbound. The SCALE trial showed ~8.4% average weight loss at 56 weeks. It requires daily injections vs weekly for Wegovy/Zepbound. For most new patients, providers now preferentially prescribe weekly semaglutide or tirzepatide.

Our projections show three scenarios based on clinical trial data. "Average" reflects the mean weight loss in published trials. "Low" approximates the 5th–25th percentile response (patients who respond less well). "High" approximates the 75th–95th percentile (strong responders). About 50% of patients fall near the average line; outliers exist in both directions.

This calculator provides estimates based on published trial averages. Clinical trial populations may differ from you — trials typically use structured diet and exercise programs alongside medication. Real-world results may be somewhat lower than trial results. Use this as a planning tool, not a guarantee. Consult your provider for individualized expectations.

GLP-1 medications do reduce appetite and caloric intake on their own. However, clinical trials that achieved 15–21% weight loss used structured reduced-calorie diets alongside the medication. Patients without any dietary changes still lose weight, but results are typically lower. Most providers recommend combining GLP-1 therapy with dietary changes and increased physical activity for best results.