Research

Hormonal

Oral estrogen therapy in postmenopausal women causes adverse body composition changes (increased fat mass, decreased lean body mass) compared to transdermal estrogen, mediated by a first-pass hepatic suppression of lipid oxidation and IGF-I levels.

If you are using estrogen replacement therapy, the method of delivery matters for your body shape. Oral estrogen (pills) can lead to increased body fat and loss of muscle mass in postmenopausal women, likely due to how the liver processes the hormone. Transdermal estrogen (patches) avoids these specific metabolic shifts. Discuss route-specific metabolic impacts with your provider if body composition is a concern.

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In summary, when compared with the transdermal route, oral estrogen reduces lipid oxidation, increases fat mass, and reduces lean body mass. The suppression of lipid oxidation during oral estrogen therapy may increase fat mass although the fall in IGF-I may lead to a loss of lean body mass.
Anthony O’Sullivan et al. · Journal of Clinical Investigation · 1998

Why this rating

Randomized crossover design with rigorous metabolic measurements, though limited by small sample size (n=18) and open-label nature.

Source

The route of estrogen replacement therapy confers divergent effects on substrate oxidation and body composition in postmenopausal women.

Anthony O’Sullivan et al. · Journal of Clinical Investigation · 1998

DOI 10.1172/jci2773

crossover · n=18Cited 208×
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DOI resolved against Crossref · corpus check 2026-06-10

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