A systematic review published March 2, 2026 in JAMA Internal Medicine reported a sex difference in GLP-1 weight loss. Across six trials with 19,906 participants, women lost an average of 10.9% of body weight. Men lost 6.8%. The authors, led by G. Caleb Alexander of the Johns Hopkins Bloomberg School of Public Health, called GLP-1 weight loss in women vs men the one clear exception in an otherwise consistent picture.
The finding does not mean every woman will lose more than every man. It describes pooled averages across large groups. Individual results vary widely, and many factors shape them. This guide explains what the review measured, how big the gap is, which explanations are plausible, and what the result means for treatment decisions.
What the Research Actually Found
The review covered 41 articles describing 64 randomized trials of GLP-1 receptor agonists. It was prospectively registered (PROSPERO CRD42024572444) and followed PRISMA reporting rules. The drugs included semaglutide, liraglutide, exenatide, lixisenatide and dulaglutide. Of the 48 trials that could be individually characterized, 21 (43.8%) tested semaglutide and nine (18.8%) tested dulaglutide. The mean trial enrolled 1,181 participants.
The team looked for differences in treatment effect by age, sex, race, ethnicity, baseline body mass index and baseline HbA1c. Only sex showed a clear difference.
| Subgroup | Trials | Participants | Result |
|---|---|---|---|
| Sex | 6 | 19,906 | Women 10.9% (95% CI 7.0 to 14.8) vs men 6.8% (95% CI 4.6 to 9.0) |
| Age | 7 | 4,314 | No significant heterogeneity |
| Race | 9 | 25,229 | No significant heterogeneity |
| Ethnicity | 7 | 8,328 | No significant heterogeneity |
| Baseline BMI | 15 (three analyses) | 9,473 | No significant heterogeneity |
| Baseline HbA1c | 4 | 1,886 | No significant heterogeneity |
Readers should note three details. First, the sex outcome was percentage change in weight, while age, BMI and HbA1c were analyzed as change in kilograms. Second, only four of the six trials individually showed a statistically significant advantage for women. Third, the reported between-group heterogeneity test had a P value of .08, so the pooled gap is suggestive and consistent in direction but not overwhelming in statistical terms.
Percentage Loss Versus Kilograms Lost
Percentage loss and absolute loss tell different stories. Women on average weigh less at baseline. A given percentage therefore equals fewer kilograms. The table below uses hypothetical baseline weights for illustration only. These are not trial values.
| Illustration | Baseline weight | Average percent loss | Resulting loss |
|---|---|---|---|
| Hypothetical woman | 90 kg | 10.9% | about 9.8 kg |
| Hypothetical man | 105 kg | 6.8% | about 7.1 kg |
| Hypothetical woman | 100 kg | 10.9% | about 10.9 kg |
| Hypothetical man | 100 kg | 6.8% | about 6.8 kg |
Absolute numbers depend on starting weight, so percentage change is the standard comparison in obesity research.
What Earlier Evidence Adds
Other reviews of GLP-1 drugs have examined sex subgroups, but they often draw on the same trials. Overlapping trials do not provide independent confirmation. Anyone comparing syntheses should check which trials each one included, which drugs, and whether the population had obesity or type 2 diabetes. The Alexander review also excluded tirzepatide, because it activates both GIP and GLP-1 receptors.
| Review feature | JAMA Internal Medicine 2026 |
|---|---|
| Included studies | 41 articles, 64 randomized trials |
| Sex-stratified data | 6 trials, 19,906 participants |
| Medications | Semaglutide, liraglutide, exenatide, lixisenatide, dulaglutide |
| Outcome | Percent change in body weight by sex |
| Pooled estimate | Women 10.9%, men 6.8% |
| Main limitations | Few trials reported sex-specific weight data; borderline heterogeneity test; tirzepatide excluded |
Why Weight Loss May Differ Between Women and Men
The authors offered three possible explanations. They suggested a synergy between GLP-1 drugs and estrogen, differences in how women’s bodies process the drug, and lower average body weight in women. These are hypotheses. The included trials did not directly test them.
Body Composition and Hormonal Factors
Women typically carry a higher proportion of body fat and a different fat distribution than men. Lower body weight can also mean a higher drug exposure per kilogram when doses are fixed. Hormones such as estrogen influence appetite and energy balance in animal and human research. Menopausal status may matter as well.
None of this proves a mechanism. Most trials did not report body composition, menopausal status or hormone levels. Attributing the gap to estrogen or any single factor would go beyond the evidence.
Treatment Indication and Study Design
Trials differ in ways that can shape average weight loss. Programs for people with obesity usually use higher doses and lifestyle support. Trials in type 2 diabetes often produce smaller weight changes. Trial length, dose, dropout and adherence also vary. If women were enrolled more often in certain trial types, the pooled gap could reflect design as much as biology.
Do All GLP-1 Medicines Produce the Same Pattern?
No. The category is broad, and the drugs differ in target, dose and approved use.
| Medicine | Receptor target | Typical labeled use (US examples) | Trial context | Key safety points |
|---|---|---|---|---|
| Semaglutide | GLP-1 | Wegovy for chronic weight management; Ozempic for type 2 diabetes | Large obesity and diabetes programs | Boxed warning on thyroid C-cell tumors; GI effects |
| Liraglutide | GLP-1 | Saxenda for weight management; Victoza for type 2 diabetes | Earlier obesity and diabetes trials | Boxed warning on thyroid C-cell tumors; GI effects |
| Dulaglutide | GLP-1 | Trulicity for type 2 diabetes | Diabetes and cardiovascular trials | Boxed warning on thyroid C-cell tumors; GI effects |
| Exenatide and lixisenatide | GLP-1 | Type 2 diabetes | Older diabetes trials | GI effects; label-specific warnings |
| Tirzepatide | GIP and GLP-1 (dual) | Zepbound for weight management; Mounjaro for type 2 diabetes | Phase 3 obesity trials | Boxed warning on thyroid C-cell tumors; GI effects |
Approvals vary by country, so readers should check their national regulator and the current prescribing information. For context, the semaglutide 2.4 mg STEP 1 trial reported 14.9% weight loss at 68 weeks versus 2.4% with placebo. The tirzepatide phase 3 trial cited in the review reported 15.0% to 20.9% loss across doses versus 3.1% with placebo. Those results are overall averages, and the Alexander review did not establish that the sex gap is identical across drugs. Related reading is available in the guides on semaglutide and obesity treatment and on GLP-1 medicines and type 2 diabetes.
What Determines an Individual’s Response?
Sex is one factor among many. The table summarizes what is known and unknown.
| Factor | Evidence strength | Potential influence | What remains uncertain |
|---|---|---|---|
| Sex | Moderate (pooled trials) | Higher average percent loss in women | Mechanism; consistency across drugs |
| Dose and titration | Strong | Higher doses generally produce more loss | Best dose for each person |
| Adherence and persistence | Strong | Stopping early reduces benefit | Reasons for discontinuation |
| Side effects | Strong | Nausea and vomiting can limit dose or adherence | Who tolerates which dose |
| Lifestyle support | Strong in trials | Diet and activity counseling add to drug effect | Intensity needed in routine care |
| Baseline BMI and HbA1c | Moderate | Little evidence of differing percent response | Interaction with sex |
| Age, race and ethnicity | Moderate | No significant differences found | Under-representation in trials |
| Treatment duration | Strong | Loss plateaus after many months | Long-term maintenance |
Weight loss usually plateaus after about a year of treatment. Stopping also matters. In the STEP 1 extension, participants regained about two thirds of their lost weight within a year of stopping semaglutide. A tirzepatide trial showed a similar pattern when participants switched to placebo. Obesity is a chronic condition, and the benefit of these drugs depends on continued use alongside lifestyle support.
Sex alone cannot predict who will respond. Many men lose more than the female average, and many women lose less. Early reassessment, usually within the first months, helps clinicians identify who is benefiting. For related background, see the overview of evidence-based weight management.
Safety, Access and Treatment Decisions
Gastrointestinal effects are the most common side effects. They include nausea, vomiting, diarrhea and constipation, and they tend to be worst during dose increases. Serious warnings in current US labels include thyroid C-cell tumors (as a boxed warning), pancreatitis, gallbladder disease and dehydration that can harm the kidneys.
Contraindications include a personal or family history of medullary thyroid carcinoma and multiple endocrine neoplasia type 2. Pregnancy needs particular care. Labels advise stopping before a planned pregnancy, and the exact interval differs by product. Tirzepatide’s label also advises that oral contraceptive effectiveness may be reduced after starting or increasing the dose, so patients should discuss backup methods.
Cost and supply remain barriers in many countries. Insurance coverage differs for weight management and diabetes indications. Patients should not change doses or stop a prescribed medicine because of group averages. The table lists useful topics for a prescriber visit.
| Topic | Clinical question | Information needed | Reason for review |
|---|---|---|---|
| Indication | Is this drug approved for my goal? | Weight, BMI, diabetes status | Labels differ for obesity and diabetes |
| Dose plan | How will the dose increase? | Titration schedule | Reduces side effects |
| Side effects | What should prompt a call? | Severe pain, persistent vomiting | Pancreatitis and dehydration risk |
| Other medicines | Any interactions? | Full medicine list, contraceptives | Absorption and effectiveness changes |
| Pregnancy plans | When should I stop? | Planned timeline | Label-specific advice |
| Expectations | What counts as a good response? | Early weight targets | Allows timely reassessment |
| Maintenance | What happens if I stop? | Long-term plan | Weight regain is common |
| Cost and access | Is coverage available? | Insurance, supply | Prevents interrupted treatment |
What Researchers Need to Investigate Next
Most trials were not designed to test sex differences. Future studies need adequate numbers of women and men, with outcomes reported by sex. They should record body composition, menopausal and hormonal status, treatment persistence, adverse events and long-term maintenance.
Researchers also need to ask whether the gap persists for newer drugs, including dual and triple agonists, and whether eligibility rules or dropout patterns shape who appears in the data. Until then, the sex difference is best read as a signal worth testing rather than a settled rule.
Conclusion
The best available pooled evidence shows that women lost more weight on GLP-1 receptor agonists than men, 10.9% versus 6.8%. The same review found no significant differences by age, race, ethnicity, baseline BMI or HbA1c. That consistency is reassuring for people of different backgrounds. The sex gap is real in the data, but it is an average and not a universal biological rule.
Treatment decisions should rest on individual assessment, including health history, goals, side effects, cost and the ability to continue therapy. Future research on mechanisms, long-term maintenance and personalization will clarify why responses differ. For now, the most useful message is that these medicines work for many people, results vary, and a clinician should guide dosing and monitoring.
Medical disclaimer: This content is for general education and does not replace individual medical advice. Do not start, stop or change any medicine without consulting a qualified healthcare professional.
FAQ
Q: Do women lose more weight than men on GLP-1 medicines?
A: On average, yes. A 2026 JAMA Internal Medicine meta-analysis found 10.9% weight loss in women and 6.8% in men across six trials. Individual results vary widely.
Q: Does semaglutide work differently in women and men?
A: Semaglutide was the most studied drug in the review. The review pooled several GLP-1 drugs, so it did not prove an identical gap for semaglutide alone.
Q: Why might average weight loss differ by sex?
A: Authors suggested estrogen interactions, differences in drug processing and lower average body weight in women. These ideas were not directly tested in the trials.
Q: Does the research apply to tirzepatide?
A: No. The review excluded tirzepatide because it targets both GIP and GLP-1 receptors. Separate studies are needed for dual agonists.
Q: How much weight do people lose in GLP-1 clinical trials?
A: It depends on the drug and dose. Semaglutide 2.4 mg produced 14.9% loss at 68 weeks in STEP 1, while tirzepatide trials reported 15.0% to 20.9% across doses.
Q: Can individual treatment response differ from the average?
A: Yes. Averages describe groups. Many men lose more than the female average, and many women lose less.
Q: What happens to weight after stopping a GLP-1 medicine?
A: Weight regain is common. In the STEP 1 extension, participants regained about two thirds of their lost weight within a year of stopping.
Q: Should sex alone determine obesity medication choice?
A: No. Choice should reflect medical history, goals, side effects, cost, approved indications and a clinician’s judgment.