How much weight can I lose on Wegovy or Ozempic?

In the STEP-1 trial, semaglutide 2.4mg (Wegovy) produced a mean ~14.9% body weight loss at 68 weeks vs ~2.4% with placebo. Ozempic 1mg (lower dose, type 2 diabetes indication) typically yields ~6–7%. Individual response varies — about a third of patients are 'super-responders' losing 20%+; about 15% lose under 5%.

How does Mounjaro / Zepbound compare?

Tirzepatide (Mounjaro for diabetes, Zepbound for weight loss) is a dual GIP+GLP-1 agonist. SURMOUNT-1 showed mean ~22.5% weight loss at 15mg over 72 weeks — roughly 50% more than semaglutide. Wegovy HD 7.2mg (FDA approved Mar 2026) narrows the gap to ~18%. Tirzepatide remains the most effective FDA-approved GLP-1 for weight loss.

What's the typical weight loss timeline?

Loss usually starts within 4 weeks. Most patients reach about 30% of their total loss by month 3, 60% by month 6, 85% by month 12 and plateau by month 15–18. Speed depends on starting weight, dose, adherence, diet and exercise. Stopping the drug generally leads to ~⅔ of the lost weight returning within a year (STEP-4 extension data).

Do I lose muscle on GLP-1s?

Body composition studies show roughly 25–40% of weight lost on GLP-1s is lean tissue — higher than diet alone (typically 20–25%). To minimise muscle loss, hit 1.6–2.2 g/kg protein daily, perform resistance training 2–3× per week, and avoid aggressive deficits. See our Protein Intake Calculator for targets.

Is this calculator a substitute for medical advice?

No. This is an educational tool using published clinical trial averages. GLP-1 medications are prescription drugs with side effects, contraindications (personal/family history of medullary thyroid carcinoma, MEN2, pancreatitis) and interactions. Always work with a licensed prescriber and never source these drugs from unregulated suppliers.

💉 GLP-1 Weight Loss Calculator

Project your expected weight loss at 3, 6, 12 and 18 months on Wegovy, Ozempic, Mounjaro, Zepbound, Saxenda or Wegovy HD using published clinical trial averages.

Units

Current Weight (kg)

Height (cm)

Medication & Dose

Adherence Profile

⚠️ Educational tool — not medical advice. Projections use mean trial outcomes; individual responses vary widely (5%–25%+). GLP-1 medications are prescription-only and have serious contraindications including personal/family history of medullary thyroid carcinoma, MEN2, and pancreatitis. Discuss with a licensed clinician. Never source from unregulated suppliers.

How GLP-1 Receptor Agonists Drive Weight Loss

GLP-1 agonists mimic the natural gut hormone glucagon-like peptide 1. They slow gastric emptying, suppress appetite via the hypothalamus, and improve insulin sensitivity. The result for most patients is dramatically reduced food intake without willpower fatigue — typically 20–35% fewer daily calories without conscious restriction.

What the Clinical Trials Show

STEP-1 (Wegovy 2.4mg): mean −14.9% body weight at 68 weeks vs −2.4% placebo
STEP-UP (Wegovy HD 7.2mg, FDA approved Mar 2026): mean ~−18% at 72 weeks
SURMOUNT-1 (Zepbound 15mg): mean −22.5% at 72 weeks; 57% of patients lost ≥20%
SCALE (Saxenda 3.0mg): mean −8% at 56 weeks
Retatrutide Phase 2: mean −24% at 48 weeks (still in development)

Loss Trajectory

Loss is non-linear. About 30% of total loss happens by month 3, 60% by month 6, 85% by month 12, with most patients plateauing between months 15–18. The plateau occurs because metabolic adaptation reduces TDEE and the drug's anorectic effect partially offsets at lower body weight.

Maintenance & Discontinuation

STEP-4 showed that switching from active drug to placebo at week 20 caused patients to regain about ⅔ of lost weight within the next year. Current evidence suggests GLP-1s are best viewed as long-term therapy for chronic obesity, not a short course. Lifestyle work (resistance training, high-protein diet) makes maintenance after eventual discontinuation more durable.

Side Effects

Most common: nausea (~40%), constipation, fatigue, decreased appetite — usually worst in the first 4–8 weeks of dose escalation and typically improves with slower titration. Rare but serious: pancreatitis, gallstones, gastroparesis, kidney injury via dehydration. Black-box warning for thyroid C-cell tumours (MTC) — contraindicated if personal or family history of MTC or MEN2.

Protect Your Lean Mass

Roughly 25–40% of GLP-1 weight loss is lean tissue — higher than diet alone. To minimise muscle loss while on GLP-1s:

Hit 1.6–2.2 g/kg protein per day (use our Protein Intake Calculator)
Perform resistance training 2–3× per week
Avoid aggressive caloric deficits — let the drug do the work
Track body composition (DEXA, BIA) every 3–6 months, not just scale weight

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Important Note: This is an educational projection tool. GLP-1 receptor agonists are prescription drugs with material risks including pancreatitis, gallbladder disease, kidney injury, and a thyroid C-cell tumour boxed warning. Always work with a licensed prescriber, get your full medical history reviewed, and never source these drugs from unregulated compounding pharmacies or grey-market online sellers.

Related Calculators

Semaglutide & Tirzepatide Dose — mg → units conversion for compounded vials on a U-100 syringe + titration schedule.
BMI Calculator — Body Mass Index with WHO health context.
Calorie Deficit Calculator — Daily calorie target to reach a goal weight. BMR + TDEE, weeks-to-goal projection and macro split.