Weight loss drugs have changed obesity treatment, but new research suggests the results can differ sharply between women and men. A study published in Obesity found that women taking tirzepatide lost significantly more weight than men during long-term treatment.
Tirzepatide is the active ingredient in Mounjaro. The medication affects hormones involved in appetite and blood sugar control, and researchers are now getting a clearer picture of why some patients may respond more strongly than others.
The latest findings point to biological sex as an important factor. Among more than 1,000 patients, women lost about 15% of their body weight after 15 months, while men lost nearly 11%. That works out to women losing roughly 41% more weight than men.
However, it does not mean women lost 41% of their total body weight, an important distinction when interpreting the results.
Women Saw Greater Weight Loss on Tirzepatide
The analysis looked at several characteristics that might affect how much weight a person loses during treatment.
Sex was the biggest determinant of weight-loss outcomes. Women lost an average of about 15% of their starting body weight, compared with nearly 11% among men over the same treatment period.
Consider someone starting at 200 pounds as a simple example. A 15% reduction would equal about 30 pounds, while an 11% reduction would equal about 22 pounds, although individual results can vary considerably.
However, the study does not mean every woman taking tirzepatide will lose more weight than every man. Medication dose, health conditions, treatment history, age, diet, physical activity, and individual biology can all affect the final result. Still, the difference between the two groups was large enough to attract attention. Researchers found that sex had a stronger association with weight loss differences than age, race, ethnicity, or starting body mass index.
The findings also align with results from broader research involving similar GLP-1 medications. Meta-analyses covering nearly 20,000 people have found a comparable difference between female and male participants. Across those analyses, women lost roughly 11% of their body weight, while men lost around 7%. Once again, sex showed a stronger link with differences in weight loss than several other common patient characteristics.
Why Mounjaro May Affect Women Differently
Scientists do not yet have one clear explanation for the gap. One possible answer lies in how male and female bodies process and remove medications from the bloodstream. Researchers have suggested that women may clear certain GLP-1 medicines from the body more slowly. Slower clearance could keep drug concentrations higher for longer periods, potentially increasing the medication’s effects on appetite and food intake.
Body composition could also influence how medications behave. Women and men tend to have different average proportions of body fat, muscle, and water, which can affect how some drugs move through the body.
These differences do not automatically explain the results, but they give researchers several biological factors to investigate. More detailed studies could identify which mechanisms account for the larger average response observed among women.
Age, Diabetes, and Tirzepatide Dose Also Mattered
That does not mean tirzepatide stops working after age 60. Older adults still experienced meaningful average weight loss, but the reduction was smaller than the average recorded among younger participants.
Researchers also found greater weight loss among participants without type 2 diabetes. Similar differences have appeared in other trials of medications used for obesity and blood sugar management.
Previous use of weight loss medication also appeared to matter. Participants who had never taken a weight loss drug before tended to lose more weight than people with a history of using these treatments.
