WeighWeekly / Expected loss by weight
Zepbound at 400 lbs: what the SURMOUNT-1 trial average shows
Short answer: at 400 lbs, the SURMOUNT-1 average works out to about 32 lbs by month 3 (368 lbs), 56 lbs by month 6 (344 lbs), and 84 lbs by week 72 (316 lbs, or 20.9% of your starting weight) on tirzepatide.
Zepbound at 400 lbs, week by week
| Point | % lost | Lbs lost | Weight |
|---|---|---|---|
| Week 4 (~mo 1) | 3.0% | 12.0 lbs | 388.0 lbs |
| Week 13 (~mo 3) | 8.0% | 32.0 lbs | 368.0 lbs |
| Week 26 (~mo 6) | 14.1% | 56.3 lbs | 343.7 lbs |
| Week 39 (~mo 9) | 17.5% | 69.9 lbs | 330.1 lbs |
| Week 52 (~1 yr) | 19.5% | 78.0 lbs | 322.0 lbs |
| Week 72 (~mo 17) | 20.9% | 83.6 lbs | 316.4 lbs |
Applied to a 400 lb starting weight from the mean curve in SURMOUNT-1 (2,539 adults without diabetes, 72 weeks).
Why month 1 looks broken
At 400 lbs the first four weeks average only 12.0 lbs — about 3.0% of your weight. That is not the drug failing. The starter dose is a tolerance ramp, and the steep part of the curve does not arrive until you are on a full treatment dose. Here is the schedule the trial used:
- 2.5 mg (weeks 1-4, starter dose - not a treatment dose)
- 5 mg (weeks 5-8)
- 7.5 mg (weeks 9-12)
- 10 mg (weeks 13-16)
- 12.5 mg (weeks 17-20)
- 15 mg (week 21 onward)
Zepbound is tirzepatide, the same molecule sold as Mounjaro for type 2 diabetes. The numbers here come from the 15 mg arm.
What this would cost
Zepbound without insurance: $299–449 a month for vials through LillyDirect, by dose ($299 at the 2.5 mg start, $449 from 7.5 mg). With commercial coverage and the savings card, as little as $25 a month. Last known price, Oct 7, 2026 — may have changed · confirm on LillyDirect
Compounded tirzepatide, which has no FDA approval: from $99/mo on a one-year plan, up to $399 a month on a month-to-month plan. Compounded tirzepatide price → Price checked Oct 27, 2026 · joinem.co; Oct 27, 2026 · medgm.org
Same starting weight, other drugs
| Drug | Week 52 weight | Total lost |
|---|---|---|
| Zepbound (this page) | 322.0 lbs | 78.0 lbs (19.5%) |
| Wegovy at 400 lbs | 342.0 lbs | 58.0 lbs (14.5%) |
Other starting weights on Zepbound
300 lbs 325 lbs 350 lbs 375 lbs see all
Questions people actually ask
How much weight will I lose in the first month on Zepbound at 400 lbs?
About 12.0 lbs, taking 400 lbs to roughly 388 lbs. Month 1 is the flattest stretch of the whole curve because you are still on the starter dose, which exists to let your gut adjust, not to drive loss. Anything from almost nothing up to about 20 lbs sits inside the normal spread for month 1.
Is 84 lbs guaranteed?
No. These are trial averages. In SURMOUNT-1 the spread was wide: a large minority lost far more than average, and a real share of people lost under 5% of their weight. Dose, how long you stay on it, and whether you hit a protein target all move your own number.
What is the fastest part of the curve?
Roughly months three to eight, once you are on a full treatment dose. In this scenario the average runs near 0.63% of body weight per week through the early titration and then steepens before flattening out toward week 72.
What to do with this number
- Compare a stall against the trial curve — most "plateaus" are the curve flattening on schedule.
- Protein target — 1.2-1.6 g per kg of goal weight (about 0.55-0.7 g per lb) is what protects muscle while you lose.
- Weekly tracker — weigh on the same day, same conditions, and read the trend not the day.
- What it costs and where to get it.
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Educational only, not medical advice. Numbers are published trial averages, not a prediction for any individual. Dosing decisions belong with your prescriber.