Average Weight Loss on Zepbound and Wegovy: What Women Lost in the Trials

The short answer

In their main trials, women and men together lost an average of 15.0% to 20.9% of their body weight on Zepbound over 72 weeks, depending on dose, and 14.9% on the Wegovy injection over 68 weeks. Placebo groups lost about 3%. Most people in both trials were women: 68% in the Zepbound trial and 74% in the Wegovy one.

Elena Voss is a mother writing for mothers, not a treating clinician, and holds no medical license. Every clinical figure here is cited inline to its primary source, the trial or the FDA label, so you can check it. This is background reading, not medical advice.

What did each trial actually find?

The two numbers people quote come from two separate trials, each against placebo, in adults with obesity or overweight and no diabetes.

Zepbound (tirzepatide), SURMOUNT-1. 2,539 adults, mean starting weight 104.8 kg (about 231 lb), randomized to 5, 10 or 15 mg weekly or placebo for 72 weeks, including a 20-week dose-escalation period. Mean weight change was −15.0%, −19.5% and −20.9% by dose, against −3.1% on placebo. At 15 mg, 57% of participants lost 20% or more of their weight, against 3% on placebo¹.

Wegovy injection (semaglutide 2.4 mg), STEP 1. 1,961 adults, 68 weeks. Mean change was −14.9% versus −2.4% on placebo, or −15.3 kg (about 34 lb) against −2.6 kg. Half the semaglutide group (50.5%) lost 15% or more².

Two newer pills sit on the same scale. The Wegovy tablet at 25 mg produced −13.6% versus −2.2% at 64 weeks in OASIS 4³. Orforglipron, sold as Foundayo, produced −7.5% to −11.2% across three doses against −2.1% on placebo at 72 weeks in ATTAIN-1⁴.

The pound columns are simple arithmetic: the trial's average percentage applied to a starting weight. They are not what any one woman lost. An average hides a wide spread, and no trial compared these drugs against each other, so reading down the column is a rough guide, not a ranking.

What if you are not average?

The thresholds show the spread better than the mean does. On Zepbound 15 mg, 91% of participants lost at least 5% of their weight, which means roughly one in eleven did not¹. On the Wegovy injection, 86.4% lost at least 5% and 69.1% lost at least 10%, so about three in ten stayed under 10%². A slower result than the average is common, not a sign that something is wrong.

Do women lose more than men?

This is the question the averages skip, and the honest answer is: probably yes, but the best evidence for it is weaker than the headline trials.

Start with what the labels say. Both the Zepbound and Wegovy prescribing information state that weight reduction was observed irrespective of sex, alongside age, race and starting BMI. Neither label prints separate figures for women and men^5,6. The main SURMOUNT-1 and STEP 1 papers report their subgroups in supplementary files, and those figures are not reproduced here.

Three studies do publish a split.

SURMOUNT-J, a Zepbound trial in Japan. In a prespecified subgroup analysis of 225 adults, the difference from placebo at week 72 was numerically larger for women: −17.5% at 10 mg and −24.9% at 15 mg, against −15.1% and −18.1% for men. The authors call these differences numerical, and the groups are small⁷.

A Mayo Clinic cohort on tirzepatide. Among 1,039 adults who stayed on tirzepatide for at least 12 months in routine care (57% women), women lost 15.1% of their body weight at 15 months against 10.7% for men. Female sex predicted greater loss after adjusting for diabetes, prior obesity drugs, weight-promoting medications and dose. Age did not⁸.

An Italian cohort on GLP-1 drugs in type 2 diabetes. Across 7,847 adults followed for a median of four years, women lost more weight than men after adjustment, and more women reached 5% loss (66.5% versus 58.0%) and 10% loss (40.0% versus 30.7%). The gap held across the different drugs and after accounting for weight-adjusted dose⁹. These patients had diabetes, which is a different population from the weight-loss trials.

So the direction is consistent across three very different settings. What is missing is a large, prespecified, sex-stratified result from the trials the drugs were approved on.

Does menopause change the result?

Less than many women fear, at least on tirzepatide. A post hoc analysis of women in SURMOUNT-1 sorted them by reproductive stage. On tirzepatide, average weight loss was 26% in premenopausal women, 23% in perimenopausal women and 23% in postmenopausal women, against 2% to 3% on placebo. Between 97% and 98% of women in every stage lost at least 5%. The analysis was funded by the manufacturer and done after the fact, which limits it, but the pattern was similar in two other SURMOUNT trials¹⁰.

For the hormonal side of that question, GLP-1s and menopause weight covers what the trials could and could not test.

How long does it take?

The 72-week and 68-week figures are end-of-trial numbers, and the early months look slower for a reason built into the dosing. Zepbound steps up every four weeks, and SURMOUNT-1 allowed up to 20 weeks of escalation before anyone reached 15 mg¹. Wegovy also climbs in four-week steps to 2.4 mg⁶. The 2.5 mg Zepbound starting dose is not a maintenance dose at all. A woman comparing her third month to the trial average is comparing a partial dose to a full one.

What predicts doing better or worse?

The cohorts above point to the same few factors. In the Mayo data, greater loss was tied to female sex, no type 2 diabetes, no previous obesity medication, no other drugs that promote weight gain, and a higher dose⁸. Diabetes shows up in the trials too: the Zepbound label's second trial, run in 938 adults with type 2 diabetes, reports −12.8% and −14.7% at 10 and 15 mg, below the figures from the trial without diabetes⁵.

And the average only holds while the drug is taken. What happens after stopping is a separate question, covered in coming off a GLP-1.

How strong is this evidence?

The overall averages are about as solid as obesity medicine gets: large, placebo-controlled, peer-reviewed trials with figures that match the FDA labels. The women-versus-men gap is weaker. It rests on one small subgroup analysis from a single country, one retrospective clinic cohort and one diabetes registry study, all pointing the same way. A published, prespecified sex analysis of SURMOUNT-1 or STEP 1 would settle it. Until then, the fair reading is that women in these studies tend to lose as much as or more than men, and nobody should promise you a specific number.

If you are comparing the drugs themselves, Zepbound vs Wegovy for mothers and the semaglutide vs tirzepatide board go further.