GLP-1 Weight Loss Calculator
Estimate your projected weight loss on GLP-1 medications like Ozempic, Wegovy, Mounjaro, and Zepbound. Week-by-week projections based on clinical trial data. 100% private — nothing leaves your browser.
How GLP-1 Medications Work for Weight Loss
GLP-1 receptor agonists like semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) work by mimicking the natural incretin hormone GLP-1. They slow gastric emptying, reduce appetite, and improve insulin sensitivity. These medications signal the brain's satiety centers, helping patients feel full with smaller meals. Originally developed for type 2 diabetes, their weight loss effects have made them among the most prescribed medications worldwide. Clinical trials consistently show significant and sustained weight reduction when combined with lifestyle changes.
Ozempic vs Wegovy vs Mounjaro Compared
Ozempic (semaglutide up to 1.0mg) is FDA-approved for diabetes but widely used off-label for weight loss, producing around 10% body weight reduction. Wegovy delivers the same molecule at a higher dose (2.4mg), approved specifically for weight management with ~15% loss in the STEP 1 trial over 68 weeks. Mounjaro (tirzepatide) is a dual GIP/GLP-1 agonist — the SURMOUNT-1 trial showed up to 22.5% weight loss at the 15mg dose over 72 weeks, making it the most effective option currently available. Zepbound is the weight-management branded version of tirzepatide. Oral semaglutide 50mg (Wegovy pill) offers similar efficacy to injectable Wegovy in a daily tablet form.
What to Expect Week by Week on GLP-1
Weight loss on GLP-1 medications follows a logarithmic pattern — faster in the first few months, then gradually slowing as you approach your plateau. Most patients notice reduced appetite within the first 1-2 weeks. Significant scale changes typically appear by week 4-8. The dose titration schedule means you start low and increase gradually, so early weight loss may be modest. Peak weight loss velocity usually occurs between months 3 and 6, with most of the total loss achieved by month 12-16. Maintaining results requires ongoing treatment — studies show patients who discontinue often regain 50-70% of lost weight within a year.
Nutrition Tips While on GLP-1 Medication
Protein intake is critical during GLP-1 treatment. Rapid weight loss can lead to muscle loss, so aim for 1.2 to 1.6 grams of protein per kilogram of body weight daily. Prioritize lean meats, fish, eggs, Greek yogurt, and legumes. Eat protein first at each meal before carbohydrates and fats. Stay well-hydrated — these medications can cause dehydration. Eat slowly and stop at the first sign of fullness. Avoid high-fat and greasy foods which can worsen gastrointestinal side effects. A moderate calorie deficit of around 500 calories below your TDEE, combined with the appetite-suppressing effect of GLP-1, produces optimal results without excessive muscle loss.
Understanding Your Projected Results
This calculator uses a logarithmic decay model calibrated against published clinical trial outcomes. The formula accounts for medication type, dose, and treatment duration. Real-world results vary based on adherence, diet quality, exercise habits, starting BMI, metabolic health, and genetic factors. Higher starting weights typically produce greater absolute weight loss. The projections assume consistent medication use at the selected dose — dose titration periods and treatment interruptions will affect actual outcomes.
Frequently Asked Questions
How accurate is this GLP-1 weight loss calculator?
This calculator uses a logarithmic decay model calibrated against data from major clinical trials (STEP 1, SURMOUNT-1). It provides estimates based on average outcomes — individual results can vary by 30-50% depending on diet, exercise, genetics, adherence, and metabolic health. Use the results as a rough guide, not a guarantee.
How much weight can I expect to lose on Ozempic?
Ozempic (semaglutide) at the maintenance dose of 1.0mg typically produces about 10% body weight loss over 68 weeks based on clinical trials. At the starter dose of 0.25mg, expect around 4%. For higher weight loss, Wegovy (semaglutide 2.4mg) achieves approximately 15% over the same period.
What is the difference between Ozempic and Wegovy?
Both contain semaglutide, but Ozempic is FDA-approved for type 2 diabetes (max 2.0mg dose) while Wegovy is specifically approved for weight management at a higher 2.4mg dose. Wegovy follows a structured dose-escalation from 0.25mg to 2.4mg over 16 weeks. The weight loss effects are more pronounced with Wegovy due to the higher dose.
How does Mounjaro compare to Ozempic for weight loss?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist, while Ozempic targets only GLP-1. In clinical trials, tirzepatide 15mg achieved up to 22.5% body weight loss compared to semaglutide 2.4mg at 15%. However, direct head-to-head trial data is still emerging. Mounjaro generally shows greater weight loss but may have different side effect profiles.
Why is protein important while taking GLP-1 medications?
GLP-1 medications can cause significant weight loss that includes both fat and muscle. Adequate protein intake (1.2-1.6g per kg body weight) helps preserve lean muscle mass during rapid weight loss. Muscle preservation is crucial for maintaining metabolic rate, physical function, and long-term weight maintenance. Resistance training combined with high protein intake provides the best outcomes.
How long does it take to see results on GLP-1 medications?
Most patients notice reduced appetite within 1-2 weeks of starting treatment. Measurable weight loss typically begins by week 4-8. The most rapid weight loss occurs between months 3 and 6, with the rate gradually slowing as you approach your maximum response. Full results are usually achieved by months 12-16 of consistent treatment.
What happens if I stop taking GLP-1 medication?
Research shows that most patients regain 50-70% of lost weight within 12 months of discontinuing GLP-1 medications. The appetite-suppressing and metabolic effects reverse when the medication is stopped. This is why many healthcare providers recommend long-term or indefinite treatment, combined with sustained lifestyle changes in diet and exercise to help maintain results.