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What weight loss to expect, and when

About this page. Written by the GLPInfo editorial team with AI assistance from the official sources listed at the end, and approved by the site owner before publication. It has not been reviewed by a named clinician. Published 27 Aug 2026 · last updated 27 Aug 2026 · next scheduled review 27 Nov 2026.

This page is information, not medical advice. It never tells you which medicine, dose or format is right for you: those decisions sit with you and a qualified prescriber. Spotted an error? Tell us and we'll fix it fast.

Every figure here comes from the published trials, which measured averages over 64 to 72 weeks in people who also received structured diet and activity support. Averages are not promises: individual variation in the trials was wide in both directions, and anyone selling you a week-by-week schedule is selling.

The shape of the curve

All four medicines produce the same broad shape. The early weeks are modest, because doses start low and climb slowly: the titration period is about tolerability, not maximum effect. The steepest average loss comes through the middle months once effective doses are reached. The curve then flattens toward a plateau as the trials approach their endpoints, with most of the average loss accrued well before the final weeks.

The endpoint averages, with their trials

At 72 weeks, tirzepatide 15mg averaged about 20.9% body-weight reduction (SURMOUNT-1). At 68 weeks, semaglutide 2.4mg averaged 14.9% (STEP 1). Over 64 weeks of treatment, the oral semaglutide 25mg tablet averaged about 14% (OASIS 4). At 72 weeks, orforglipron's highest dose averaged 12.4% among completers and 11.1% counting everyone randomised (ATTAIN-1). Placebo groups averaged roughly 1-3% in each. These are different trials with different populations: the numbers anchor expectations, they do not rank the medicines head-to-head.

The plateau is not failure

Plateauing is what the trials show happening to nearly everyone: the body reaches a new equilibrium at the treated set point. It is the moment people are most tempted to stop, self-escalate or switch, and all three are prescriber conversations rather than solo decisions. What maintains the result is continuing what achieved it: the withdrawal evidence is set out honestly in stopping GLP-1 treatment.

What this means for budgeting

The trial curves are the honest case for budgeting on the ongoing price over many months rather than the first-month offer: the result builds over a year and more. The true cost guide shows 3, 6 and 12-month totals per provider at today's prices, and each medicine's dose schedule shows what the climb itself costs.

Frequently asked questions

How much weight will I lose in the first month?

Less than the headlines: the first weeks run at low titration doses chosen for tolerability. The trials' averages accrued over a year and more, with the steepest period in the middle months. A slow first month is the schedule working, not failing.

Why have I plateaued?

Because that is what the curves do: average loss flattens as the body reaches a new equilibrium. The trials' endpoint averages, with their trial names and caveats, are above. If a plateau arrives much earlier than expected, that is a prescriber conversation about dose, adherence and expectations.

Do results differ between the four medicines?

The trial averages differ (from about 11-12% to about 21% at maximum doses over 64-72 weeks), but they come from separate trials and only one head-to-head exists (SURMOUNT-5, tirzepatide vs semaglutide injection). The comparisons lay out the evidence per pair: Mounjaro vs Wegovy, Foundayo vs Mounjaro, Foundayo vs Wegovy pill.